This edition of the conference will take place in Saint Petersburg State University, Russia, 2020-2021. The first part (online) will be held from 11th to 17th October 2020. The second part (in person) will be held from 28th June to 3rd July 2021. For the second part of the conference, a new call for abstracts will be organized from January to March 2021.
The conference is devoted to the actual nuclear and high energy physics problems and their applications. This is the eldest international nuclear conference in Russia (since 1951). It is also one of the eldest conferences in Europe.
The aim of the conference is the discussion of the latest results on
• Experimental study of properties of atomic nuclei;
• Experimental study of mechanisms of nuclear reactions;
• Theory of atomic nucleus and fundamental interactions;
• Theory of nuclear reactions;
• Application of nuclear physics methods in related fields of science and technology.
The program will include plenary (30+5 min), oral (20+5 min) and poster presentations.
The working language of the Conference is Russian and English.
The theoretical description of nuclear magnetic excitations within self-consistent models is hampered by the fact that the parameters of the underlying energy-density functionals (EDF) are determined without accounting for magnetic properties which leaves the EDF’s spin parameters uncertain. In a recent paper 1 we have explored low-lying M1 excitations in $^{208}$Pb within a self-consistent random-phase approximation (RPA) based on a Skyrme EDF. By re-tuning the spin parameters we managed to reproduce the experimental key quantities: energy and the strength of the $1_1^+$ state as well as mean energy and summed strength of the M1 resonance in 208Pb in the interval 6.6-8.1 MeV.
However, the observed fragmentation of the M1 resonance and its total width are not described within the RPA. Here we have to go beyond RPA by proceeding to the self-consistent time blocking approximation (TBA) which includes particle-phonon coupling and which we use actually in its renormalized version [2]. The Skyrme EDF with the basis parametrization SKXm [3] was used both in the RPA and in the TBA. The spin-related EDF parameters $x_W$, $W_0$, $g$ and $g'$ were refitted as explained in 1. The theoretical and “experimental” strength functions were obtained by folding the discrete spectra with a Lorentzian of half-width Δ = 20 keV. The results are shown in the figure. The TBA, in contrast to the RPA, reproduces the experimental splitting of the M1 resonance into two components separated by the dip near 7.4 MeV. But the total width of the resonance is still underestimated and the detailed fragmentation structure of the experimental curve is not quantitatively reproduced.
The study of nuclear giant resonances has long been a subject of extensive theoretical and experimental research. The multipole response of nuclei far from the $\beta$-stability line and the possible occurrence of exotic modes of excitation present a growing field of research. In particular, the study of the isoscalar giant monopole resonances (ISGMR) in neutron-rich nuclei is presently an important problem not only from the nuclear structure point of view [1] but also because of the special role they play in many astrophysical processes such as prompt supernova explosions [2] and the interiors of neutron stars [3]. One of the successful tools for describing the ISGMR is the quasiparticle random phase approximation (QRPA) with the self-consistent mean-field derived from Skyrme energy density functionals (EDF) [4]. Such an approach can describe the properties of the low-lying states reasonably well by using existing Skyrme interactions. Due to the anharmonicity of the vibrations there is a coupling between one-phonon and more complex states [5]. The main difficulty is that the complexity of calculations beyond standard QRPA increases rapidly with the size of the configuration space, and one has to work within limited spaces. Using a finite rank separable approximation for the residual particle-hole interaction derived from the Skyrme forces one can overcome this numerical problem [6-8].
In the present report, we analyze the effects of phonon-phonon coupling (PPC) on the E0 strength distributions of neutron-rich tin isotopes. Using the same set of the EDF parameters we describe available experimental data for $^{118,120,122,124}$Sn [9] and give prediction for $^{130,132}$Sn [10]. The effects of the PPC leads to a redistribution of the main monopole strength to lower energy states and also to higher energy tail.
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5. V.G. Soloviev // Theory of Atomic Nuclei: Quasiparticles and Phonons. 1992. Bristol/Philadelphia.
6. N.V. Giai, Ch. Stoyanov, V.V. Voronov // Phys. Rev. C. 1998. V. 57. P. 1204.
7. A.P. Severyukhin, V.V. Voronov, N.V. Giai // Phys. Rev. C. 2008. V. 77. P. 024322.
8. A.P. Severyukhin, V.V. Voronov, N.V. Gia // Eur. Phys. J. A. 2004. V. 22. P. 397.
9. T. Li, U. Garg, Y. Liu et al. // Phys. Rev. C. 2010. V. 81. P. 034309.
10. N.N. Arsenyev, A.P. Severyukhin // in preparation.
The $\beta$-decay properties are very important for understanding the nuclear structure evolution at extreme N/Z ratios, for analysis of radioactive ion-beam experiments, and modeling of the astrophysical r-process. For this reason, the $\beta$-decay properties of r-process “waiting-point nuclei” $^{129}$Ag, $^{130}$Cd, and $^{131}$In provides valuable information, with important tests of theoretical calculations. One of the successful tools for nuclear structure studies is the quasiparticle random phase approximation (QRPA) with the self-consistent mean-field derived from the Skyrme interaction. The framework allows to relate the properties of the ground states and excited states through the same energy density functional. On the other hand, it would be desirable to overcome the discrepancies between the theoretical predictions low-energy $1^+$ spectrum using the one-phonon QRPA wave functions of the daughter nucleus and the measurements [1]. We have generalized the approach to the coupling between one- and two-phonon terms in the $1^+$ wave functions and the tensor force effects on the $\beta$-decay rates of neutron-rich nuclei [2]. We applied the influence of the phonon-phonon coupling on the multi-neutron emission probabilities [3]. The new calculation is extended by enlarging the variational space for the $1^+$ states with the inclusion of the two-phonon configurations. The dominant contribution to the additional $1^+$ states comes from the $[3^+\otimes2^+]_{QRPA}$ two-phonon configurations constructed from the charge-exchange $3^+$ phonons. A correlation is found between the low-lying E2 transition strengths of the parent and daughter isobaric companions. Using the same set of parameters this correlation is studied for $^{126,128,130}$In and $^{126,128,130}$Cd.
1. A. Etilé et al.// Phys. Rev. C. 2015. V.91. P.064317.
2. A.P. Severyukhin, V.V. Voronov, I.N. Borzov, N.N. Arsenyev, Nguyen Van Giai// Phys. Rev. C. 2014. V.90. P.044320.
3. A.P. Severyukhin, N.N. Arsenyev, I.N. Borzov, E.O. Sushenok// Phys. Rev. C. 2017. V.95. P.034314.
The semi-microscopic particle-hole dispersive optical model (PHDOM), in which main relaxation modes of high-energy particle-hole-type nuclear excitations are together taken into account [1], has been implemented for describing various giant resonances in medium-heavy closed-shell nuclei (see, e.g., Refs. [2,3]).
A lot of experimental data concerned with giant resonances in medium-heavy open-shell spherical nuclei makes reasonable an extension of PHDOM for taking nucleon pairing into account. In the present work, an extended PHDOM version is developed in a “high-energy limit” employing the simplest BCS-model.
The proposed version is implemented for describing main properties of Isoscalar Giant Monopole Resonance (ISGMR) and Isobaric Analog Resonance (IAR) in a number of tin isotopes.
From studies of ISGMR in a chain of tin isotopes one gets information about isotopic dependence of nuclear-matter incompressibility coefficient (see, e.g., Ref. [4]).
Existence and properties of IAR are closely related to the isospin and symmetry in nuclei. Using previous studies of ISGMR [2], IAR and its overtone [3] as a base, we employ the extended PHDOM version for describing strength function, projected transition density, probabilities of direct one-nucleon decay of ISGMR, and main relaxation parameters of IAR (partial proton and spreading widths, resonance-mixing phase).
The obtained results are compared with respective experimental data related to ISGMR (Ref. [4] and references therein) and IAR [5].
This work was partially supported by the Russian Foundation of Basic Research (grant No. 19-02-00660).
The particle-hole (p-h) dispersive optical model (PHDOM) developed recently [1] is adopted and implemented for describing main properties of Isoscalar Giant Multipole Resonances (ISGMPR) up to L=3 in medium-heavy closed-shell nuclei. The overtones of monopole and quadrupole isoscalar giant multipole resonances are also studied. Being considered in a large excitation-energy interval, the main properties include the following energy-averaged quantities: the strength function related to an appropriate probing operator; the projected (i.e., related to the mentioned operator) one-body transition density; partial probabilities of direct one-nucleon decay. Unique abilities of PHDOM are conditioned by a joint description of the main relaxation modes of high-energy p-h configurations associated with a given giant resonance. Two modes (Landau damping and coupling of mentioned configurations to the single-particle continuum) are described microscopically in terms of Landau-Migdal p-h interaction and a phenomenological partially selfconsistent mean field. Another mode, coupling to manyquasiparticle states (the spreading effect), is described phenomenologically in terms of the imaginary part of the properly parameterized energy-averaged p-h self-energy term. The imaginary part determines the real one via a microscopically-based dispersive relationship. Using previous studies of the isoscalar giant monopole resonance in 208Pb [2, 3] as a base, we specify and markedly extend the above-outlined PHDOM description of mentioned giant resonances in closed-shell nuclei 40,48Ca, 90Zr, 132Sn, 208Pb. The model parameters related to a mean field and p-h interaction are taken from independent data accounting for the isospin symmetry and translation invariance of the model Hamiltonian. Parameters of the strength of self-energy term imaginary part are adjusted to reproduce in PHDOM-based calculations of ISGMPR total width (full width at half maximum (FWHM)) in each nucleus under consideration. The calculation results are compared with available experimental data. Some of results are compared with those obtained in microscopic Hartree-Fock calculations [4]. These comparisons confirm the statement that PHDOM is a powerful tool for describing ISGMPR in medium-heavy closed-shell nuclei. Extension of the model on taking nucleon pairing into account in open-shell spherical nuclei is in order.
This work was supported in part by the Russian Foundation for Basic Research (grant No. 19-02-00660).
The evolution of single-particle energies $\it E_{nlj}$ of near to spherical medium and medium- heavy nuclei as they approached neutron drip line was studied within the dispersive optical model (DOM) [1]. The main attention was paid on the dependence of the diffuseness parameter $\it a_{HF}$ of the Hartree-Fock component of the potential on neutron-proton asymmetry and its influence on the evolution. It was shown that the agreement with the available experimental data was improved if $\it a_{HF}$ depended on neutron-proton asymmetry:
$\it a_{HF}= \it a_{HF}^0\pm \it a_{HF}^1(N-Z)/A$, + for n, – for p . (1)
In other words, the diffuseness $\it a_{HF}$ increased when the Fermi energy goes up. The dependence (1) differs from that of the global diffuseness parameter $\it a_V^{KD}$ of the traditional optical model potential [2]. The parameter $a_V^{KD}$ decreases with increasing mass number A of the nucleus for both neutrons and protons. The dependence (1) leads, in particular, to the following: more pronounced inversion of the $2\it s_{1/2}–1\it d_{3/2}$ proton levels in stable Са isotopes and the $1\it g_{7/2}–2\it d_{5/2}$ proton levels in stable Sn isotopes; more pronounced evolution of the energy gap between the neutron states $1\it f_{5/2}$ and $2\it p$ in the stable $1\it f-2\it p$– shell nuclei; better agreement with the experimental energies $\it E_{nlj}$ of the $1\it d_{3/2}$ neutron state in neutron-rich Si isotopes [3] comparing to the parameter $\it a_{HF} = \it a_V^{KD}$ (see fig). Thus, dependence (1) improves the predictive power of DOM with respect to the nuclei far from the $\beta$-stability valley.
In nuclear reactions induced by low-energy charged particles, atomic electrons can participate in the process by screening the nuclear charge and so, effectively reduce the repulsive Coulomb barrier. Consequently, the measured cross section is enhanced by an effect called electron screening. In numerous experiments, different research groups [1-4] obtained extremely high values of electron screening, that are in several cases (depending on target-nuclei environment) more than an order of magnitude above the prediction based on available theoretical model in adiabatic limit [5].
Nevertheless, even as a considerable amount of experimental data was collected over the past twenty years, a suitable theory, which can give an explanation of this effect, has not yet been found. However, electron screening is very important in nuclear astrophysics. For nucleosynthesis calculations, precise reaction rates should be known at very low energies. At these energies charged-particle-induced reaction cross sections become difficult to measure due to their sharp drop with decreasing energy. Nowadays, the energies of astrophysical interest can only be reached in underground laboratories with high-current low energy accelerators [6]. In spite of that, even when the lowest energies are reached, the measurements do not give the nuclear cross section, since the reaction rate in the laboratory is always influenced by the atomic electrons that surround the reacting nuclei.
Trying to understand this process, the effect of electron screening has been investigated by our group [7-9]. We measured the highest value of electron screening in a graphite target. The measured value is about a factor of 50 above the adiabatic limit prediction and much higher than any potential measured so far. Further, our results pointed out that the Z dependence of the screening is even higher than Z$ ^{2} $ instead of expected linear dependence. This rules out the theory based on static electron densities. In order to explain our data, we proposed a new model assuming that an electron is caught in the attractive potential of the two approaching nuclei, similar to the potential of the hydrogen molecular ion [8].
At the moment, our group is focusing on studying the electron screening effect in deuterium implanted titanium targets using the $ ^{19} $F(d,p)$ ^{20} $F reaction. Titanium is particularly suitable because it can absorb deuterium up to the stoichiometric ratio of 1:2. It is also very interesting for our investigations due to particular dependence of the electron screening potential on the concentration of deuterium in titanium [3]. Deuterium depth profiles of Ti targets were analysed by nuclear reaction analysis. In order to get a better insight into the condition of the titanium lattice itself, targets were additionally analysed by X-ray diffraction, thermal desorption and Raman spectroscopy. Our goal is to find a different value of the screening potential in two titanium targets and then to understand which parameters of those targets differ and cause high electron screening. An overview of our work will be given and our latest results will be presented.
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[9] M. Lipoglavšek et al., Phys. Lett. B, 773:553, 2017.
The fast proton induced p – processes reactions play a key role in the astrochemical elements yields of the big bang nucleosynthesis for standard cosmology. Astrophysical concurrence of several p - process mechanisms in the production of p – nuclei was analyzed for proton energy up to 25 MeV.
Cross sections of proton induced reactions and contribution of each nuclear reaction mechanism for each process are evaluated theoretically and measured experimentally at Electrostatic Generator EG-5 from FLNP for incident protons up to 5 - 10 MeV. For protons up to 4-8 MeV compound processes are dominant and they are described applying Hauser – Feshbach statistical approach. At higher energies direct and pre-equilibrium mechanisms cannot be neglected. Contribution to the cross section of direct mechanism was determined using DWBA approach and pre-equilibrium processes by exciton model. Parameters of optical potential and levels density for incident and emergent channels were also extracted. Cross sections, parameters of potentials and levels density are of a great importance for astrophysical reactions rates estimation and for estimation of the astrochemical elements abundance.
The statistical uncertainties reduction was done by Talys using a Bayesian Monte Carlo procedure based on the EXFOR database and they were in fair agreement with the standards. The uncertainties in the nuclear element abundances originating from the combined effect of experimental and theoretical errors leading to total uncertainties in the final abundances were determined.
Present results are obtained in the frame of the bilateral scientific JINR - Romania projects dedicated to nuclear reactions for astrophysics developed at JINR Dubna basic facilities.
The phenomenon of dissociation of relativistic nuclei observed with a unique completeness in the nuclear track emulsion (NTE) makes it possible to study ensembles of nucleons and lightest nuclei of interest to nuclear cluster physics and astrophysics [1]. The advantages of the NTE technique include a record space resolution in determining emission angles for recognition relativistic ${}^{8}$Be and ${}^{9}$B decays among the He and H projectile fragments. The decays are identified by the invariant mass $M^*$ defined by the sum of all products of 4-momenta $P_i$ of relativistic fragments He and H. The components $P_i$ are determined by the fragment emission angles under the assumption of conservation a projectile momentum per nucleon. Recently, in the events of relativistic dissociation of ${}^{9}$Be, ${}^{10}$B, ${}^{10}$C, ${}^{11}$C nuclei were identified unstable ${}^{8}$Be and ${}^{9}$B nuclei by invariant mass approach [2]. The successful identification of ${}^{9}$Be nuclei allowed us to cross to the problem of identifying triples of alpha particles in the Hoyle state (HS) in the dissociation of relativistic nuclei. Production of $\alpha$-particle triples in the HS in dissociation of ${}^{12}$C nuclei at 3.65 and 0.42 $A$ GeV in NTE was investigated [3]. Contribution of the HS to the dissociation ${}^{12}$C $\to$ 3$\alpha$ is (11 $\pm$ 3) %. Analysis of data on coherent dissociation ${}^{16}$O $\to$ 4$\alpha$ at 3.65 $A$ GeV is revealed the HS contribution of (22 $\pm$ 2) %. These observations indicate that it is not reduced to the unusual ${}^{12}$C excitation and, like ${}^{8}$Be, is a more universal object of nuclear molecular nature. Reanalysis of data on dissociation of heavier nuclei (Ne, Si, Kr and Au) pointed out to significant contribution of HS in the n$\alpha$-channels. The analysis of the NTE layers exposed to relativistic ${}^{14}$N nuclei is resumed in the HS context. Video collection of relativistic nuclei dissociation events in NTE obtained using a microscope and a digital camera can be found [4].
References:
1. P.I.Zarubin // Lect. Notes in Physics, Clusters in Nuclei, 2014. V.875(3) P.51; arXiv: 1309.4881.
2. D.A.Artemenkov, A.A.Zaitsev, P.I. Zarubin // Phys. Part. Nucl. 2017. V.48 P.147; arXiv:1607.08020.
3. D.A.Artemenkov et al. // Rad. Meas. 2018. V.119. P.119; arXiv:1812.09096.
4. The BECQUEREL Project. http://becquerel.jinr.ru/movies/movies.html.
The properties of an extreme state of nuclear matter, the Quark-Gluon Plasma (QGP), are studied in experiments at RHIC and LHC with heavy-ion datasets collected at ultrarelativistic energies. The QGP consists of asymptotically free quarks and gluons which move freely over distances large in comparison to the typical size of a hadron. If the nuclear matter produced in heavy-ion collisions reaches thermalization, its behavior will be dominantly governed by non-trivial collective effects, like anisotropic flow. In non-central heavy-ion collisions, the initial ellipsoidal volume containing the interacting nuclear matter is anisotropic in the coordinate space, due to the geometry of non-central collisions. Multiple interactions within this anisotropic volume cause the anisotropy to be transferred from coordinate space into momentum space. This transfer is the anisotropic flow phenomenon. Flow measurements have provided the key constraints on transport properties of QGP (e.g. on its shear viscosity), and these results helped a great deal in establishing the perfect fluid paradigm about QGP.
In this contribution, we introduce new experimental methods and observables for anisotropic flow analyses in high-energy physics, which can provide further and independent constraints on QGP properties. The cornerstone of this approach are multiparticle azimuthal correlations, from which the new observables, dubbed higher-order Symmetric Cumulants, have been recently derived in [1], as well as new estimators for symmetry-plane correlations in [2]. Both theoretical predictions and first experimental results from ALICE Collaboration are presented and discussed.
[1] C. Mordasini, A. Bilandzic, D. Karakoc, and S. F. Taghavi, ``Higher-order Symmetric Cumulants,'', accepted by Physical Review C, arXiv:1901.06968 [nucl-ex].
[2] A. Bilandzic, M. Lesch, S. F. Taghavi, "New estimator for symmetry plane correlations in anisotropic flow analyses", accepted by Physical Review C, arXiv:2004.01066 [nucl-ex].
The collective expansion of the color-deconfined fireball created in relativistic heavy-ion collisions maps the initial state of the quark-gluon plasma (QGP) to the final-state particle spectrum.
The LHC experiments are completing the flow harmonic measurements at the highest energies to date as well as improving flow harmonic correlation techniques to understand the properties of the QGP and the full evolution of the heavy-ion collisions.
In this talk, a brief summary of the flow measurements developed in recent years and their implications to constrain the initial conditions and transport properties of heavy-ion collisions will be discussed.
The ALICE experiment is designed to study the hot and dense medium, the quark-gluon plasma, produced in ultra-relativistic heavy-ion collisions at the LHC. Measuring the
production of hadrons with large Q2 transfer in these collisions provides the possibility to explore one of the most spectacular effects -- parton energy loss in hot QCD matter. By varying the observables among light- and heavy-flavor hadrons and fully reconstructed jets and by changing the colliding systems from pp to p-Pb to Pb-Pb, one can explore the transport properties of hot QCD matter in great detail.
In this talk we present an overview of recent ALICE results on high-pT hadron and jet production in pp, pA and AA collisions at LHC energies.
Femtoscopy is an important tool to measure spatial and temporal characteristics of the collision system. In this talk, the results of one-dimensional pion femtscopic analysis performed for d+Au collisions at $\sqrt s_{NN}$ =200 GeV will be shown. We will present various dependences of the invariant radii on pair transverse momentum and particle multiplicity per event. The physics implications of the resulting radius from the 1D pion femtoscopic analysis in this small system will be discussed.
The $φ$ meson has a small inelastic cross section for interaction with nonstrange hadrons, therefore it is less affected by late hadronic rescattering and better reflects the initial evolution of heavy ion collisions. Small systems, such as $p$+Al, $p$+Au, and $^3$He+Au, can help us understand whether the suppression of hadron yields in the region of intermediate to large transverse momenta is associated with hot (QGP) or cold nuclear matter effects. In this talk we will present a study devoted to the phi meson production in small collisions systems at $\sqrt{s{_{_{NN}}}}=200$ GeV as measured by the PHENIX experiment at RHIC. The $φ$-meson production shows a small system size dependence in the most central $p$+Al, $p$+Au, $^3$He+Au collisions, and the nuclear modification factors are consistent with those of the $π^0$ within uncertainties for all three collision systems. Implications for hadronization and strangeness production will be discussed.
The primary goal of the ultra-relativistic heavy-ion collision program at the Large Hadron Collider (LHC) is to study the properties of the Quark-Gluon Plasma (QGP), a novel state of strongly interacting matter which exists in the early universe. Anisotropic flow, which quantifies the anisotropy of the momentum distribution of final state particles, is sensitive to the fluctuating initial conditions and the transport properties of the created QGP. The successful description of the measured anisotropic flow coefficients by hydrodynamic calculations suggests that the created medium behaves like a nearly perfect fluid. However, the observation of collective flow phenomena in high energy proton-lead and proton-proton collision triggers intense discussions. Whether the smallest droplet of QGP has been produced in these collisions or other physics mechanisms will be attributed to this phenomenon, is under debate.
In this talk, I will present the latest developments of flow studies at the LHC, including both recent theoretical model calculations and experimental measurements in proton-lead collisions at $\sqrt{s_{_{\rm NN}}} =$ 5.02 TeV and proton-proton collisions at $\sqrt{s} =$ 13 TeV. I will especially highlight the current challenge of the hydrodynamic description on multi-particle cumulants measurements, and try to answer whether we have the evidence of the creation of a small droplet of QGP in these small collision systems.
Using the Gribov–Glauber model for photon–nucleus scattering and a generalization of the vector meson dominance (VMD) model for the hadronic structure of the photon, we make predictions for the cross sections of coherent and incoherent photoproduction of rho-mesons in Pb-Pb ultraperipheral collisions (UPCs) at the LHC. We find that the effect of inelastic nuclear shadowing is significant and leads to an additional 40% (25%) suppression of the coherent (incoherent) cross section. Our approach provides a very good description of the ALICE data on coherent rho photoproduction in Pb-Pb UPCs at 2.76 and 5.02 TeV. Comparing our predictions to those of the STARlight Monte-Carlo framework, we observe very significant differences.
We argue that $p_T$ distribution data from the LHC on the invariant differential yield of the charged primary particles in Pb–Pb collisions at 2.76 TeV with six centrality bins contains several $p_T$ regions with special properties. These distributions were analyzed by fitting the data with exponential functions. We conclude that the regions reflect features of fragmentation and hadronization of partons through the string dynamics. The nuclear transparency results in negligible influence of the medium in the III region ($p_T$ > 17−20 GeV/c), which has highest $p_T$ values. The effects and changes by the medium start to appear weakly in the II region (4−6 GeV/c < $p_T$ < 17−20 GeV/c) and become stronger in the I region ($p_T$ < 4−6 GeV/c). It seems that the II region has highest number of strings. The increase in string density in this region could lead to fusion of strings, appearance of a new string and collective behavior of the partons in the most central collisions. These phenomena can explain anomalous behavior of the Nuclear Modification Factor in the II region. We propose the II region as a possible area of Quark Gluon Plasma formation through string fusion. The first $p_T$ regions are the ones with the maximum number of hadrons and minimum number of strings due to direct hadronization of the low energy strings into two quark systems–mesons.
The BESIII experiment, installed at the BEPCII electron positron collider in Beijing, has acquired large data sets at center-of mass energies between 2.0 GeV and 4.6 GeV. One of the main aspects of the BESIII physics program is to test the understanding of QCD at intermediate energies. Applying different experimental techniques, form factors of hadrons are measured. An overview of the recent results at BESIII will be reported.
The results of new comprehensive data analyses of geoneutrino measurements in Borexino experiment at underground Gran Sasso national laboratory (LNGS) are presented. The analysis is the result of 3262.74 days of data between December 2007 and April 2019 with improved analysis techniques and optimized data selection, which includes enlarged fiducial volume and sophisticated cosmogenic veto. Geo-neutrino fluxes generated in the processes of radioactive decay of elements in the depths of the Earth carry information about the radioactive elements inside our planet and its geological structure. The measured geoneutrino signal at LNGS is compared to the expectations of different geological models. The extraction of the mantle signal using knowledge of the signal from the bulk lithosphere and the consequences of the new geoneutrino measurement with respect to the Earth’s radiogenic heat are discussed.
Solar neutrino spectrum measurement plays a crucial role for solar metallicity determination. 127I(nu,e)127Xe reaction is sensitive to CNO and boron components of the solar neutrino spectrum due to the relatively high threshold (662 KeV).
For neutrinos with energies upper S_n = 7.246 MeV 127I(nu,e) capture produces 126Xe + n. The concentration ratio of 127Xe and 126Xe could clarify parameters of high energy solar neutrino spectrum and neutrino oscillations. We present production rate estimation for of 127Xe and 126Xe based on experimental strength function from 127I(p,n)Xe reaction.
Intensive experimental searches for axions and axion-like particles are currently supported by two main reasons: firstly, axions solve the CP problem of strong interactions and, secondly, axions are well-motivated candidates for the role of dark matter particles. If axions exist, the Sun should be a powerful source of such particles. The expected energy spectrum of solar axions, like the spectrum of solar neutrinos, contains both continuous spectra and monochromatic lines. Moreover, the fluxes of solar axions should be directly proportional to the fluxes of neutrinos; only the proportionality coefficients remain unknown, which are determined by the effective coupling constants of the axion with photons, electrons, and nucleons. The report discusses some past, present and future experiments aimed at detecting solar axions and axion-like particles. This work was supported by the Russian Foundation for Basic Research (project nos. 16-29-13014, 17-02-00305 and 19-02-00097).
Recent achievements in experimental neutrino physics allow studying the Sun's deep interior through the high precision spectroscopic measurements of the solar neutrinos. Currently the most sensitive solar neutrino detector Borexino, which takes data in Gran Sasso national laboratories in Italy, is able to separately measure neutrinos produced in various nuclear reactions of the solar proton-proton fusion chain. Recent Borexino results indicate the preference of high over low metallicity solar models - the step forward of extreme importance for solar physics. Borexino's measurements contribute to neutrino physics as well: for the first time single neutrino detector examines simultaneously the MSW-LMA neutrino oscillation paradigm both in the vacuum and the matter dominated regimes. In this talk I overview the major Borexino accomplishments.
The results of a low-energy neutrino search with the Borexino detector in coincidence with gamma-ray bursts (GRB), solar flares (SF) and gravitational wave (GW) events are presented. The correlated events with energies greater than 0.25 (1.0) MeV, positioned inside the detector fiducial volume and not identified as alpha-particles or fast cosmogenic decays (neutrino-like events) were searched within various time windows centered around the GRB or GW detection time. The events correlated with SF were searched in the time window corresponding to SF duration. All count rates obtained are in good statistical agreement with the expected count rate of natural, cosmogenic and neutrino backgrounds in the detector. As a result, we have obtained the best current upper limits on all flavor neutrino fluences associated with these astrophysical sources for neutrino energy below 5-7 MeV. The obtained limits allow to exclude the solar neutrino explanation of the anomaly of the run 117 in the Homestake River neutrino experiment.
The DANSS detector is a movable neutrino spectrometer currently operating under one of industrial reactors of the Kalinin Nuclear Power Plant. Its plastic scintillator composition with no flammable or otherwise dangerous materials allows placing it close to the reactor core thus benefiting from ample antineutrino flux. Complex multilayers of the active and passive shielding and high segmentation of the sensitive volume makes it possible to reconstruct up to 5000 IBD events per day with residual cosmic background on the level of few percent. The data are recorded in three different positions from the center of the reactor core, which gives a great opportunity to search for short-range neutrino oscillations to a hypothetical sterile state in a wide range of mixing parameters.
In this talk the DANSS collaboration reports the results on short-range oscillations, which are obtained from the 2016-2019 data set comprising about three million IBD events. The dependence of the measured antineutrino spectrum on the nuclear fuel composition is also presented. Finally, the long-term measurements of the reactor power are discussed, illustrating the excellent DANSS capacity for independent high-precision monitoring of nuclear reactor.
The neutrino scattering on nuclei in hot and dense matter relevant for core collapse supernovae, neutron star mergers, and proto-neutron stars is considered accounting for magnetization. At finite temperature neutrinos undergo exo- and endo-energetic scattering [1] on nuclei due to the neutral current Gamow-Teller component. The energy transfer cross section in neutrino-nuclon scattering is shown to change from positive to negative values at neutrino energies four times the matter temperature. Effects in neutrino transport and spectra are discussed.
[1] V. N. Kondratyev, et al. // Phys. Rev. C 2019. V. 100, 045802
The Impurity Components in the 7Be Solar
Neutrino Flux
Romanov Yu.I.
Kosygin Russian State University, Moscow, Russia
E-mail: romanov.yu.i@mail.ru
In the present work, a development [1], the flavor structure of the 7Be
solar neutrino (SN) flux is investigated.
The electron spectrum of the (v_e ) ̅e-scattering differs from the fairly flat
spectra of all neutrinos. Such difference will open the way for the Borexino
Collaboration to search for an antineutrino admixture in the SN flux [2].
If the part of this flux transforms into neutrinos of the second and third
generations and related antiparticles v ̅e, the total electroweak spectrum of recoil electrons can be written in the form:
(dσ/dT)tot= P(v_e ) (dσ(vee))/dT +P_(v_(μ,τ) ) (dσ(v_(μ,τ) e))/dT +P_(¯v_e ) (dσ( v ̅ee))/dT , (1)
where T is the kinetic energy of the final electron.
The table
P_(¯v_e ) (dσ/dT)tot
0 [0.28; 0.36]
0.05 [0.27; 0.39]
0.1 [0.27; 0.41]
0.2 [0.26; 0.46]
0.3 [0.25; 0.51]
shows the results of calculations based on the Borexino data: a limit of the conversion probability P(v_e→v ̅e ) < 0.35 (90% C.L.) for 862 keV 7Be neutrinos [2], under the assumption of v_e transition to other active neutrino flavors, the SN survival probability P(v_e )= 0.51 ± 0.07 [3].
Each spectrum is presented by ten values of the differential cross sections, corresponding to the recoil electron kinetic energy for the kinematically allowed escape angles, determined by the segment [0°; 90°].
The graphical image of these spectra is presented in the form of figures.
DEAP-3600 is a low-background liquid argon detector for a direct WIMP (Weakly Interacting Massive Particles) dark matter search. The detector consists of 3279 kg of LAr contained in a spherical acrylic vessel. Liquid argon is an excellent scintillator, transparent to its own scintillation light. Scintillation is detected by photomultiplier tubes, and pulse shape discrimination is used to differentiate between nuclear recoils, which may result from WIMP-nucleus scattering or some rarer backgrounds, and electronic recoils, the most abundant backgrounds which predominantly come from the beta-decay of Ar39. Ar39 is an inevitable component of background created by interaction of Ar40 with cosmic rays. Here we report the results of an analysis of a 231 live-days data set taken during the first year of operation. We also describe a detailed background model, WIMP selection criteria and future plans including blinding scheme for analysis and machine learning techniques for discrimination against alpha-decays in the neck of the detector.
Scanning electron microscopy has been extensively used for the material characterization of objects of artistic and archaeological importance, especially in combination with energy dispersive X-ray microanalysis (SEM-EDX) [1, 2], and become an indispensable tool in delineating the degradation processes of ancient as well as modern materials in art and archaeology [1].
Rock art is found on every continent and comprises one of the most abundant and informative of archaeological artefacts [3]. In general, paintings are made by mixing dry pigments with a liquid binder either of animal or plant origin [1, 3]. After drying the paint layer, a new layer can be applied [1]. Three main problems arising when studying the composition of ancient paintings are the determination of the paint production technology and raw material sources, as well as the way of how the paint is applied [2].
Present study is devoted to the elemental and mineral composition of pigments from the cave paintings of the Ignatievskaya cave [4] and pictographs of the Idrisovskaya cave [5] (Southern Urals, Russia) using SEM-EDS. SEM images and elemental mapping of carbon sputtered samples were performed using JEOL JSM-6390LV with INCA Energy 450 EDS spectrometer with accelerating voltage of 20 kV at the IGG UB RAS.
It has been shown that the main inorganic components of the pigments are goethite and hematite-containing ochres and carbon, most likely derived from burnt bone; organic binder is likely of animal origin. The technology of dye manufacture could include the stage of thorough grinding of inorganic raw materials with a binder, and the application of paint could occur in layers.
For the images of open-air pictographs, the presence of calcium oxalates, formed as a result of the interaction of organic components with rock matter, is characteristic, which can perform a stabilizing function and protect pigments from weathering and reliably fix the dye to the substrate as it was pointed out by [6].
Fig. 1. BSE image of red pigment from the Idrisovskaya cave. Fine-grained calcite crystals of the wall and paint layers.
The work was carried out at the UB RAS “Geoanalytic” Center for Collective Use within IGG UB RAS state assignment № АААА-А18-118053090045-8.
References:
1. M. Schreiner, M. Melcher, K. Uhlir, Anal Bioanal Chem. 387(3), 737 (2007).
2. A.S. Pakhunov, E.G. Devlet, I.A Karateev et al., Crystallography Reports 63(6), 1027 (2018).
3. R. Reese, M. Hyman, M. Rowe et al., Journal of Archeological Science 23, 269 (1996).
4. V.T. Petrin, Paleoliticheskoe svyatilishche v Ignatievskoi peshchere na Yuzhnom Urale. Novosibirsk: Nauka, 207 p. (in Russian) (1992).
5. V.N. Shirokov, Uralskie pisanitsy. Yuzhny Ural. Ekaterinburg: AMB, 128 p. (in Russian) (2009).
6. J. Russ, W.D. Kaluarachchi, L. Drummond et al., Studies in Conservation 44(2), 91 (1999).
Synchrotron and neutron imaging are the unique tools that allow non-destructive studies of the internal structure of bulk metal objects. It's very significant for the assessing artifacts preservation, clarifying the manufacturing technology and localization of possible decorative ornaments.
A complex of imaging techniques including X-ray computed tomography, synchrotron radiography and tomography at the KISI "Kurchatov" synchrotron radiation source and neutron tomography at the neutron source Research reactor IR-8 are used at the Kurchatov Institute. These methods are complementary, since the different nature of radiation interaction with matter.
We have studied some artifacts from the most famous mound of Medieval Rus’ – Chernaya Mogila (Black Grave mound, X century, Chernigov) from the collection of State Historical Museum in Moscow. The presented results of X-ray, synchrotron and neutron studies of metal artifacts showed rich ornamentation of weapons and allowed us to study on the hidden features. In particular:
- the silver decoration of Scandinavian style was detected on the object with unknown function, later it was supposed that this object was ‘barbarian scepter’ [1];
- a part of a mark on a blade fragments was recognized [2];
- details of a manufacturing technology were clarifying for composite construction of the helmet [2];
- some items (stirrup, spear-heads etc.) were recognized inside the sintered bulk of weapon [2].
References:
1. V. Murasheva, S. Kainov, Е. Kovalenko, et al., ‘Barbarian Scepters’ of the Viking Age from the Chernaya Mogila burial mound at Chernigov (present-day Ukraine) (in press).
2. E.S. Kovalenko, V.P. Glazkov, M.M. Murashev, et al., X-ray, synchrotron and neutron imaging of metal artifacts from the Chernaya mogila (in press).
Measuring the natural abundance of isotopes and the variations in their ratios in the archaeological hard tissues (such as bones and teeth) can provide important information about the evolution and migration of humans and animals and their origin. Strontium isotopes are among the most effective for characterizing the prehistoric mobility of humans and animals [1]. $^{87}$Sr/$^{86}$Sr isotope ratio incorporates into the surrounding biosphere from underlying bedrocks and is practically not fractionated by biological organisms. Since Sr can replace Ca in the hydroxyapatite crystal lattice of bones and teeth, $^{87}$Sr/$^{86}$Sr ratio can be directly attributed to the isotopic ratio of the geochemical province where humans and animals reside [1].
The work presents the method of $^{87}$Sr/$^{86}$Sr isotope ratio analysis in biogenic apatite by multi-collector (MC) ICP-MS using the standard-sample bracketing (SSB) technique with preliminary chromatographic separation of Sr.
All works were performed in cleanrooms (ISO 6, 7) of the Zavaritsky Institute of Geology and Geochemistry, UB RAS. Single-step chromatography technique modified from [2] and described in detail in [3] was applied for strontium isolation using SR resin (100–200 mesh, Triskem®). Sr isotope measurements were carried out using a MC ICP-MS Neptune Plus (Thermo Fisher Scientific, Germany) equipped by the ASX 110 FR sample introduction system (Teledyne CETAC, USA) fitted by PFA micro-flow nebulizer (50$\mu$L min$^{−1}$) connected to a quartz spray chamber.
Mass bias was corrected by the combination of exponential law normalization and standard-sample bracketing (SSB), the $^{87}$Sr/$^{86}$Sr ratio was normalized by the value of 88/86=8.375209 [4]. In addition, interference correction was provided by accounting of $^{86}$Kr and $^{87}$Rb by $^{83}$Kr/$^{86}$Kr=0.664162, $^{83}$Kr/$^{84}$Kr=0.201579 and $^{87}$Rb/$^{85}$Rb=0.386 ratios (also normalized). Subsequently, the normalized values were additionally corrected by the mean value variation of SRM-987 “bracketed” each two samples from the reference value of 0.710245 (GeoReM database, http://georem.mpch-mainz.gwdg.de/).
The analysis of Bone Meal SRM 1486 and Bone Ash SRM 1400 standard reference materials was carried out, and the expanded uncertainty was calculated. For NIST Bone Ash 1400, $^{87}$Sr/$^{86}$Sr = 0.71318 ± 0.00026, and for NIST Bone Meal 1486 $^{87}$Sr/$^{86}$Sr = 0.70933 ± 0.00022, which is in an excellent agreement with the GeoReM Database data (0.7131-0.7134) and (0.709269-0.70964), respectively. The method precision was estimated as the within-laboratory standard uncertainty (2σ) obtained for SRM-987 and was ± 0.003 %.
The developed method was applied to the strontium isotope analysis of animal and human teeth and bones from a number of archaeological sites in Russia.
The work was carried out at the “Geoanalitik” Center for Collective Use and supported by RFBR grant No. 20-09-00194.
References:
1. J.E. Ericson, Journal of Human Evolution 14, 503 (1985).
2. D. Muynck et al., Journal of Analytical Atomic Spectrometry 24, 1498 (2009).
3. A. Kasyanova et al., AIP Conference Proceedings 2174, 020028 (2019).
4. A.O. Nier, Physical Review 54, 275 (1938).
Lead isotope analysis (LIA) has been rapidly approved by archaeologists as a method for provenance studies of metal artefacts as well as glass, pottery, pigments, etc. [1, 2]. The major advantage of LIA application for provenance studies is that lead isotope ratios do not change during metallurgical processes, which means that the isotope pattern remains constant independent on the temperature of ore roasting or Red-Ox conditions of metal smelting. The pattern is therefore characteristic of a particular deposit and allows a secure assignment of the finished product to the initial raw material [1]. The modern instrumental methods of isotope analysis, in particular, mass-spectrometry, are characterized by high sensitivity and precision. Lead mass of $10^{-9}$ - $10^{-7}$ g is sufficient for a routine isotope measurement resulting in the sample mass of only tens of mg, which can be very important when working with unique and valuable archaeological artefacts.
Lead isotope measurements of a number of bronze and copper artefacts and ingots of the Bronze Age steppe Cis- and Trans-Urals of were carried out on a Neptune Plus multicollector ICP-mass spectrometer (Thermo Fisher Scientific, Germany) using Tl-normalization technique [3] after the chromatographic lead isolation. A conventional ion-exchange chromatography technique using Bio-Rad AG 1x8 resin (100–200 mesh) proposed by [4] was applied for lead isolation [5]. The calculated U(k=2) method expanded uncertainty was U($^{208}$Pb/$^{204}$Pb)=0.3%, U($^{207}$Pb/$^{204}$Pb)=0.1% and U($^{206}$Pb/$^{204}$Pb)=0.1%. All works were performed in cleanrooms (ISO 6, 7) of the Zavaritsky Institute of Geology and Geochemistry, UB RAS.
The obtained data for bronze and copper artefacts and ingots of the steppe Cis- and Trans-Urals of the Bronze Age indicate their fairly clear assignment to the ores of the Trans-Urals and Ural-Mugodzharsky or Cis-Urals ancient mining and metallurgical centers. For a number of samples studied, the interpretation is complicated. More correct comparisons will become possible only after the implementation of a large-scale program of isotopic analyzes of ore deposits and occurrences of all mining and metallurgical centers of the Bronze Age of the Southern Urals.
The work was carried out at the “Geoanalitik” Center for Collective Use and supported by RFBR grants № 18-00-00036 К (18-00-00030, 18-00-00031).
References:
1. Z.A. Stos-Gale, Isotopic Analyses of Ores, Slags and Artefacts: The Contribution to Archaeometallurgy, In: Archaeologia delle attività estrattive e metallurgiche, Firenze, 593 (1993).
2. A. Hauptmann, The archaeometallurgy of copper: evidence from Faynan, Jordan, Springer Science & Business Media, 388 p (2007) .
3. J. Woodhead, J. Anal. At. Spectrom. 17, 1381 (2002).
4. B.S. Kamber, A.H. Gladu, Geostandards and Geoanalytical Res. 33(2), 169 (2009).
5. D.V. Kiseleva, N.I. Shishlina, M.V. Streletskaya et al., Geoarchaeology and Archaeological Mineralogy (GAM 2019), Springer Proceedings in Earth and Environmental Sciences, Springer, Cham, 133 (2020).
Lead isotope analysis (LIA) is widely applied by archaeologists as a method for provenance studies of metal artifacts [1, 2]. Nevertheless, there are several issues complicating LIA interpretation of archaeological artefacts, including following [2]: 1) ore deposits can have identical or overlapping isotope compositions, even when they are geographically far apart; 2) the recycling of scrap metal has also to be taken into account, and the isotope pattern resulting from such processes cannot be compared with the original ore source; 3) the assignment of metal artefacts to a raw material source could be hindered further if ores from different sources had been smelted together [2].
The hoard found near the village of Sosnovaya Maza (Saratov region, Russia) in 1901 is the second largest hoard of the Bronze Age in Eastern Europe with its total weight of 22.5 kg. It is composed of sickles and their fragments, daggers and their fragments, and some other metal artefacts [3].
The aim of the work is to assess the homogeneity/heterogeneity of the ore base used when smelting the sickles of the Sosnovo-Mazinsky hoard and to determine the probable ore resource base or several sources of ore used for metal smelting.
The lead isotope composition of copper alloys of items from the Sosnovaya Maza hoard and bronze items of a comparative samples from the archaeological sites of the Urals and Kazakhstan was studied.
A Perkin Elmer ELAN DRC-e quadrupole ICP mass-spectrometer was used to obtain lead isotope ratios according to the methodology proposed by [4]. For Pb isolation, an extraction chromatographic column containing Pb-selective PBA052316 100-150 mm resin was used.
The comparative analysis of obtained data with the lead isotopic analysis of copper ores from ancient and modern mines of the Cis- and Trans-Urals regions allowed an assumption to be made about the probable use of several types of deposits – copper-pyrite of the Southern Urals; Late Permian oxidized ores of the Urals from the Sakmara-Samara mining and metallurgical region; the ore of the third type, characterized by highly radiogenic $^{208}$Pb/$^{204}$Pb, probably comes from the deposits of northern Kazakhstan. The variability of the lead isotopic composition of the hoard items confirms the use of several ore deposits and the re-melting of bronze scrap.
The work was supported by RFBR grant No. OFI-M 17-29-04176.
References:
1. A. Hauptmann. The archaeometallurgy of copper: evidence from Faynan, Jordan. Springer Science & Business Media, 388 p. (2007).
2. E. Pernicka et al., Jb Röm-German Zentralmuseum 31(2), 533 (1984).
3. N. Shishlina et al., Sickles from the Sosnovaya Maza hoard of the Late Bronze Age from the Lower Volga region: technological analyses, experiments and chronology (in press).
4. D. De Muynck, C. Cloquet, F. Vanhaecke, Journal of Analytical Atomic Spectrometry 23, 62 (2008).
In 2020, we celebrate 80 years since the discovery of the fundamental phenomenon - spontaneous fission of uranium - a type of radioactive decay that defines the boundaries of the Periodic system of elements. The paper with the results of research carried out by K. Petrzhak (Radium Institute) and G. Flerov (Leningrad Institute for Physics and Technology) was sent to Physical Review on June 14, 1940 and published on July 7, 1940.
The questions of the creation and development of nuclear physics in the 20-30th XX century at the Radium Institute are considered. Little-known documents and historical facts are examined to estimate the contribution of the Radium Institute - the cradle of comprehensive studies of radioactivity in Russia - to the world atomic science and technology.
The global beta-decay calculations are presented which are based on the Density Functional developed by Fayans et.al. [1] and Continuum Quasiparticle Random-Phase Approximation. The DF3+CQRPA model [2] describes the data on the half-lives and probabilities of delayed neutron emission for more than 200 (quasi) spherical nuclei with Z = 18 - 52 and T1/2 < 5c within the factor of 2 and 3 correspondingly (Fig.1). A detailed comparison with modern self-consistent models: spherical RHB + RQRPA [3], deformed FAM [4] and HFB + QRPA [5] is performed. The“sudden shortening” of the β-decay half-lives found in RIKEN for the Ni isotopes crossing the major neutron shell at N=50 [6] are addressed (Fig.2). The performance of “beyond the QRPA models” in explaining beta-decay acceleration in the 78,79Ni is discussed. Supported by the grant of Russian Foundation for Basic Research (RFBR 18-02-00670).
[1]. S.A. Fayans, S.V. Tolokonnikov, EL. Trykov, D. Zawischa., Nucl.Phys. A676, 49 (2000).
[2] I.N. Borzov., Phys. Rev. C67, 025802 (2003).
[3] T. Marketin, L. Huther, and G. Martinez-Pinedo, Phys. Rev. C 93,025805 (2016).
[4] M. T. Mustonen, T. Shafer, Z. Zenginerler, and J. Engel., Phys. Rev. C 90, 024308 (2014)
[5] K. Yoshida., Phys.Rev. C100, 024316 (2019).
[6] Z. Y. Xu et al., Phys. Rev. Lett. 113, 032505 (2014).
Development of radioactive ion beam (RIB) facilities is the highway of the low-energy nuclear physics development in the world the last 3 decades. RIB studies in Russian Federation at the moment are conducted only in one place – ACCULINNA/ACCULINNA-2 facility at Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research. However, scientific opportunities of these instruments are lower than those expected for the modern RIB center. It is proposed to develop powerful RIB facility DERICA (Dubna Electron – Radioactive Ion Collider fAcility) covering broad range of modern nuclear physics aspects (new isotope synthesis and production, its masses, lifetimes and decay modes, nuclear reactions and spectroscopy). The emphasis of the project is storage ring physics with ultimate aim of electron-RIB scattering studies in the collider experiments.
The DERICA concept combines in-flight production of RIBs by projectile fragmentation technique (primary beams up to uranium with energy ~100 AMeV), stopping RIBs by gas catcher, reacceleration by LINAC-synchrotron combination, usage of reaccelerated RIBs for reaction studies and for storage ring experiments.
Status of DERICA project and the most recent information can be obtained at http://derica.jinr.ru. Letter-of-Intent for DERICA project is published in [1].
The artificial r-(rapid)-process of nucleosynthesis goes under high neutron flux densities: the obtained neutron fluencies in the irradiated volume of thermo-nuclear devices reach ~1025 neutrons/cm2 during the time interval ~10-6 s. Under (thermo) nuclear explosions the obtained conditions in neutron flux and temperature (~ 108 °K) reach extreme values. The creation of transuranium nuclides under pulsed neutron fluxes of thermonuclear explosions is investigated by means of dynamical model (as in the kinetic model of the astrophysical rapid r-process) taking into account the time dependence of the external parameters and the processes accompanying the beta decays of neutron-rich nuclei. Time dependent neutron fluxes in the interval ~ 10-6 s (prompt rapid pr-process) were simulated within the framework of the developed adiabatic binary model (ABM) [1]. The results of calculation on the base of the ABM model are compared with the experimental date for all mass numbers in the region A = 239 – 257.
Calculations of transuranium nuclides yields Y(A) are made for six large scale explosion USA experiments ("Mike", "Anacostia", "Par", "Barbel" "Vulcan" and “Kankakee” and it were obtained good or satisfied agreement. The corresponding root-mean-square deviations (r.m.s.) of the model yields compare to the experimental data are: 91% (for "Mike"); 70% ("Anacostia"); 33% ("Par"); 29% ("Barbel"); and 45% ("Vulcan"). The beta-delayed processes are taken into account for isotope yields correction after the pulse neutron wave. The calculations include the processes of delayed fission (DF) and the emission of delayed neutrons (DN), which determine the "losing factor" – the total loss of isotope concentration in the isobaric chains. The DF and DN probabilities were calculated in the microscopic theory of finite Fermi systems [2]. Thus, it is possible to describe the even-odd anomaly in the distribution of concentrations N(A) in the mass number region A = 251 – 257. It is shown qualitatively also that the odd-even anomaly may be explained mainly by DF and DN processes in very neutron-rich uranium isotopes.
The work is supported by the Russian Foundation for Basic Research (Grant no.18-02-00670_а).
On behalf of the JUNO collaboration
The Jiangmen Underground Neutrino Observatory (JUNO) is a next generation multi-purpose liquid-scintillator neutrino experiment under construction in South China. Exploitingthe anti-neutrinos produced by the nearby nuclear power plants, JUNO will be able to study the neutrino mass hierarchy, one of the open key questions in neutrino physics. The JUNO detector structure consists of a large acrylic sphere (34.5 m diameter), containing almost 20 kton of ultra pure linear alkylbenzene with proper additives. The light produced by the scintillator will be seen by about 18,000 large photomultiplier tubes (PMT)(20”) and about 25,000 small PMTs (3”). The described central detector will be placed inside an instrumented water pool that will act both as a Cherenkov muon veto and as a shield against environmental radiation coming from the rock. A key ingredient for the measurement of the neutrino mass hierarchy is an excellent and challenging energy resolution of the central detector: 3% at 1 MeV or better is required. Beyond mass hierarchy and precision determination of the three active neutrino oscillation parameters, JUNO can give access to valuable data on many topics in physics, like supernova burst and diffuse supernova neutrinos, solar neutrinos, atmosphericand geo-neutrinos, nucleon decay, indirect dark matter searches and a number of additional exotic searches. During the presentation, the status of the design, construction and the JUNO prospects on physics will be reported.
For the KATRIN collaboration
The KArlsruhe TRItium Neutrino experiment (KATRIN) is designed to improve the existed direct limit on the effective electron antineutrino mass by an order of magnitude, with a projected sensitivity of 0.2 eV/c2 at the 90% confidence level. To achieve this KATRIN is using a windowless gaseous tritium source containing up to 100 GBq activity and electrostatic spectrometer with adiabatic magnetic collimation with resolution up to 1 eV. In spring 2019 first 521.7 hour long data taking run was performed. Data analysis provided new upper limit on the electron antineutrino effective mass 1.1 eV (90% confidence level), published at Phys. Rev. Lett. 123, 221802, November 2019. In 2020 Neutrino-4 experiment presented evidence of a sterile neutrino signal observation of with parameters sin22θ14≈0.35±0.07(5σ) and Δm214≈(7.3±0.7)eV2. KATRIN experiment is sensitive to sterile neutrino with these parameters. Last results from KATRIN project and common analysis with Neutrino-4 are presented.
The GERDA (GERmanium Detector Array) experiment, located at the Laboratori Nazionali del Gran Sasso (LNGS) of the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, searches for the neutrinoless double beta decay (0$\nu\beta\beta$) of $^{76}$Ge. During Phase II, 35.6 kg of bare high purity germanium diodes enriched in $^{76}$Ge have been deployed in liquid argon; they serve both as source and detector. The use of active background rejection methods, e.g liquid argon scintillation light read-out and pulse shape discrimination of germanium detector signals, has allowed to achieve a background index of 6·10$^{−4}$ cts/(keV·kg·yr). No evidence for 0$\nu\beta\beta$ decay has been found establishing the up-to-date most stringent half-life limit for this process in $^{76}$Ge with a sensitivity of 1.1·10$^{26}$ yr at 90$\%$ C.L. The experimental setup, the analysis procedures and the latest results of GERDA are summarized in the present work.
Ultra-high-energy cosmic rays (UHECRs) are the highest energy messengers in the universe, with energies up to $10^{20}$ eV. Studies of astrophysical particles (nuclei, electrons, neutrinos and photons) at their highest observed energies have implications for fundamental physics as well as astrophysics. The primary particles interact in the atmosphere (or in the Earth) and generate extensive air showers. Analysis of those showers enables one not only to estimate the energy, direction and most probable mass of the primary cosmic particles, but also to obtain information about the properties of their hadronic interactions at an energy more than one order of magnitude above that accessible with the current highest energy human-made accelerator.
The Pierre Auger Observatory, located in the province of Mendoza, Argentina, is the biggest cosmic ray experiment ever built. The Observatory was designed as a hybrid detector covering an area of 3000 km$^2$ and it has been taking data for more than twenty years.
In this talk a selection of the latest results is presented: the cosmic ray energy spectrum, searches for a directional anisotropy and studies of mass composition (including the photon and neutrino searches). Finally, the current upgrade ("AugerPrime“) of the Observatory, which is mostly aimed at improving the sensitivity to the particle type and mass of ultra-high energy cosmic rays, is described.
Fully self-consistent calculation of the Odd-Even Staggering (OES) of the charge radii in the long isotopic chains is presented. The nuclei around the neutron shells at N=20, 28, 50 including non-magic ones with pairing in both neutron and proton sectors are treated in the Density Functional Theory. Well-established Fayans functional DF3-a developed in [1] is used. A comparison with its new options Fy(stand) [2] and more recent Fy(∆r,HFB) [3] is performed. The performance and flexibility of the DF3-a are demonstrated. Namely, it describes better the unexpected OES reduction which was observed in the CERN-ISOLDE experiments on the charge radii of the 58-78Cu isotopes approaching the N=50 shell [3] (Fig.1). Also, the DF3-a allows one to simultaneously describe the total beta-decay energies. The latter (presented as the 3-point OES parameters in Fig.2) are more sensitive “markers” than the binding energies used in [3]. Still, the problem of the charge radii OES needs a more detailed study. A rather strong dependence of the pairing on the density gradient is needed in order to comply with the experimental data on nuclear radii [3]. Supported in part by the grant of Russian Scientific Foundation (RSF 16-12-10161).
Fig. 1. The “liquid drop” charge radii of 58-78Cu compared to the data [3] and calculation within the DF3-a functional for a few different strengths of the gradient paring term.
Fig. 2. The 3-point OES parameters ∆(3)=1/2(QA+1 -2 QA+ QA-1) for the measured total beta-decay energies Qβ and ones calculated with DF3-a for the Cu isotopic chain.
[1]. E.E. Saperstein, S. V. Tolokonnikov, Physics of Atomic Nuclei 74, 1277 (2011).
[2]. P.-G. Reinhard, W. Nazarewicz., Physical Review C95, 064328 (2017).
[3]. R.P. de Groote et.al. arXiv:1911.08765v1 (2019).
The report considers the structure of high-spin (9+) isomers and the nature of rotational bands in Ho and Dy nuclei with A= 156, 158, 160.
A detailed comparative analysis of the decay of holmium isomers into dysprosium levels (Ho → Dy) for A= 156, 158, 160 (see Fig. 1.).
Fig. 1. Decay of isomer 9+ in ${}^{156}$Ho nucleus.
1. V.G.Kalinnikov et al. // Int. conference on nuclear physics «Nuclear shells - 50 years». Summaries of reports. p. 88. Dubna, Russia, 1999.
2. K.Ya.Gromov et al. // Acta Physica Polonica, B7 (1976) 507.
The real observed excitation spectrum of deformed nuclei is complex and contains levels having both a rotational nature and levels arising from collective vibrations. The collective spectra of atomic nuclei with axial-symmetry quadrupole and octupole deformations are characterized by rotational bands with alternating parity.
Earlier energy sequences with alternating parity of deformed axial-symmetry even-even nuclei described within a collective model with non- adiabatically coupled quadrupole and octupole degrees of freedom. Satisfactorily reproduced the structure of the yrast and first non-yrast alternating-parity sequences in the rare-earth nuclei ${}^{150}$Nd, ${}^{152,154}$Sm, ${}^{154,156,158}$Gd, ${}^{156}$Dy, ${}^{162,164}$Er and the actinides ${}^{224}$Ra, ${}^{228}$Th, ${}^{232;234;236;238}$U, ${}^{240}$Pu. It should be noted that in the experiments one can observe energy bands, which cannot be explained framework the nuclei models with axially-symmetric multipole deformations. For example, the spectrum of $\gamma$–band energy levels. In present work we are attempt to describe energy spectrum of yrast-, non-yrast- and $\gamma$-bands even-even nuclei framework the model with trixial-asymmetric multipole deformations.
The self-consistent calculations with the use of functionals of both Skyrme and Fayans have been performed for the probability of E1-transitions between the first one-phonon $2^+$ and $3^-$states in Sn isotopes. Good agreement with the available experimental data has been obtained. As in our previous calculations for the quadrupole moments of the first $2^+$ [1], and $3^-$ states [2], and for the EL transitions between first $2^+$ and $3^-$ states in magic nuclei [3], we have found that two dominant contributions to observed characteristics come from new three-quasiparticle ground states correlations (GSC), which are largely due to tadpole effects, and from the nuclear polarizability. The polarizability effects reduce the E1 transition probabilities by one order of magnitude. An opposite effect of similar magnitude proves to arise from the three-quasiparticle GSCs. So, in contrast to E2 transitions, the E1 transition probability is determined by the difference between the large effects of nuclear polarizability and three-quasiparticle GSCs.
D. Voitenkov, S. Kamerdzhiev, S. Krewald, E. E. Saperstein,and S. V. Tolokonnikov, Phys. Rev. C 85, 054319 (2012).
S. P. Kamerdzhiev, D. F. Voitenkov, E. E. Sapershtein, S. V. Tolokohhikov, JETP Lett. 108, 155 (2018)
S. P. Kamerdzhiev, D. F. Voitenkov, E. E. Sapershtein,S. V. Tolokonnikov, and M. I. Shitov, JETP Lett. 106, 139 (2017).
${}^{156}$Gd-одно из изученных ядер. Причиной этого является то, что величина сечения $(n,\gamma)$ - реакции дает богатые возможности для изучения спектра излучения. Наиболее полные результаты по этому ядру представлены в работах [1,2]. В реакции $(n,\gamma)$ получены данные об уровнях ротационных полос с $K=0_{1}^{+}$ - до ${26}^{+}$, $0_{2}^{+}$ до ${14}^{+}$, $2_{1}^{+}$ до ${14}^{+}$, $0_{3}^{+}$ до ${10}^{+}$, $0_{4}^{+}$ до ${6}^{+}$, $0_{5}^{+}$ до ${4}^{+}$ и $2_{2}^{+}$ до ${4}^{+}$. Из имеющихся результатов можно сказать, что в ${}^{156}$Gd обнаружены почти все уровни до энергии возбуждения 2 МэВ.
В данном ядре известны пятнадцать состояния с $K=1_{1}^{+}$. Абсолютно большинство из них принадлежат ножничной моде и экспериментально определены вероятности М1- переходов [1,3]. Электрические характеристики низколежащих коллективных состояний экспериментально исследовались в работах [2,4], а магнитные свойства этих уровней изучались в [1,5]. Эти экспериментальные данные указывают на наличие отклонения от адиабатической теории.
В данной работе в рамках феноменологической модели [6], рассматривающей смешивание состояний низколежащих ротационных полос, описываются неадиабатические эффекты, проявляемые в энергиях и электромагнитных характеристиках. Вычислены спектр энергии, структура состояний и вероятности электромагнитных переходов.
Показано, что неадиабатические эффекты, проявляемые в энергиях и электромагнитных свойствах состояний, является результатом кориолисово смешивание состояний адиабатических полос, имеющих одинаковые моменты инерции. Ранее эта модель была применена для изучения смешивание полос состояний положительной четности изотопов ${}^{158,160}$Gd [7,8].
On the base of microscopic version of the IBM1 plus other bosons
of positive parity with spins from $0^+$ to $10^+$ properties of
yrast-band states in even Ce isotopes are studied. Parameters of
the boson Hamiltonian and interactions of the collective
quadrupole bosons with other bosons are calculated
microscopically. This study is a continuation of similar works on
the isotopes Xe and Ba [1], in which the possibilities of the
microscopic theory have been investigated in the description of
increasingly deformed nuclei.
In all considered even Ce isotopes in which there are developed
yrast-bands theoretical calculations show that at spin $I{\rm
cr}=12^+$ in $^{122-128}$Ce and at $I{\rm cr}=10^+$ in
$^{130,132}$Ce the band-crossing takes place just as in even Ba
isotopes [1]. The back-bending in moment of inertia (expect
$^{122}$Ce) at corresponding rotational frequency and minima in
$B(E2;\ I\rightarrow I-2)$ values at $I=I{\rm cr}$ serve
experimental confirmation of such calculations. In $^{122}$Ce
because of a strong interaction between two bands the moment of
inertia up to $I=14^+$ retains the square dependence on frequency.
The suggested theory satisfactory describes these experimental
facts: fig.1 present yrast-band energies (theoretical quantities
distinguish from experimental ones not more then by 60 keV), fig.2
$B(E2)$'s for $^{128}$Ce.
A non-adiabatic collective model that takes into account the relationship of rotational motion with longitudinal and transverse vibrations of the quadrupole type of the surface of the nucleus allows us to explain a number of patterns observed in the excitation spectra of deformable non-axial even-even nuclei.
Various well-known types of deviations of nuclear collective motion from purely rotational are known. As a result of these deviations, high-order effects such as "squeezing", "backbending" and "staggering" occur in the structure of the nuclear rotational spectrum.
In particular, the "staggering" effect represents the branching of rotational bands in a sequence of states that differ by several units of angular momentum. The use of discrete approximations of high-order derivatives of a given nuclear characteristic as a function of a particular physical quantity shows various forms of even-odd "staggering" effects that carry information on the fine properties of nuclear interaction and the corresponding high-order correlations in the collective dynamics of a system.
Collective excitations of even-even nuclei of a quadrupole type were studied in the framework of the approximation with arbitrary nonaxiality. In the framework of this approximation, the zigzag behavior of the $\Delta I=1$ "staggering" effect in the energy spectrum of the collective excitation of the $\gamma$-band of heavy even-even nuclei of ${}^{152}$Sm, ${}^{156}$Dy, ${}^{164,166}$Er and ${}^{230}$Th is considered. Moreover, the first and second order terms in the expansion of the rotational energy operator in the variable γ are taken into account in the description of the energy of the levels of the nuclei under consideration. It was shown that the $\Delta I=1$ "staggering" effect occurs in the case of strong coupling of the ground and $\gamma$-bands in the framework of the SU(3) dynamic symmetry.
Experiment was done by our group on $^{12}$C($^{3}$He,t)$^{12}$N reaction. The measurements were conducted at the University of Jyväskylä (Finland) using the K130 cyclotron to produce a $^{3}$He beam at E($^{3}$He)=40 MeV. The 150 cm diameter Large Scattering Chamber was equipped with three ΔE-E detector telescopes, each containing two independent ΔE detectors and one common E detector. So each device allowed carrying out measurements at two angles. The differential cross sections of the ($^{3}$He,t) reaction on $^{12}$C were measured in the c.m. angular range 8°–70°. Self-supported $^{12}$C foils of 0.23 and 0.5 mg/cm$^{2}$ thicknesses were used as targets. It should be mentioned that, before starting measurements, beam monochromatization was done [1], which made it possible to diminish beam energy spreading up to three times and obtain a total energy resolution about 140 keV. Triton angular distributions for the g.s. and three first excited states of $^{12}$N: 0.96-MeV 2$^{+}$, 1.19-MeV 2$^{−}$, and 1.80-MeV 1$^{−}$ were measured. Modified Diffraction Model (MDM) analysis [2] of ($^{3}$He,t) experimental data was done. Enhanced rms radii were obtained for the 2$^{−}$ (1.19-MeV) and 1$^{−}$ (1.80-MeV) states of $^{12}$N. It can be an argument for existence of halo in these states.
The differential cross-sections of the elastic and inelastic d + $^{13}$C scattering were measured at E(d)=14.5 and 18 MeV on U150M cyclotron of Institute of Nuclear Physics (Almaty, Kazakhstan).
The first 3.09 MeV $(1/2^{+})$ excited state of $^{13}$C nucleus is of special interest because, it is a state with increased radius, where we can talk about a neutron halo-like structure.
The most probable candidate having the structure of $\alpha$-particle condensate is still considered a known Hoyle state of 7.65 MeV (0$^{+}_{2}$) in the $^{12}$C nucleus. In the context of $\alpha$-particle hypothesis, the level of 7.65 MeV in the $^{12}$C nucleus is the simplest example of $\alpha$-particle condensate state and plays an important role in Astrophysics problem. In the work [1], it is proposed that similar Hoyle state can be detected in some neighboring nuclei, such as excited state 8.86 MeV (1/2$^{-}$) in the $^{13}$C nucleus.
In this paper we show the results of the calculations of the radii of the excited states: 3.09 (1/2$^{+}$) and 8.86 (1/2$^{-}$) which were determined by the Modified diffraction model (MDM)[2] at E(d)=14.5 MeV.
[1] M. Milin and W. von Oertzen, EPJ A V 14 (2002);
[2] A.N. Danilov et.al. Phys.Rev. C 80 (2009);
One of the main few-body reactions, in which data on nn-interaction are obtained, is the nd-breakup reaction n + $^2$H → n + n + p. However, the data on main nn interaction parameter - nn scattering length, extracted from this reaction at different energies, have a large scatter of values that exceeds the experimental errors. In [1], it was assumed that this dispersion is related to the unaccounted contribution of 3N forces depending on the energy of primary neutrons. Moreover, at low energies, the contribution of 3N forces is relatively large, while at high energies it is negligible, and we can assume that the extracted scattering length value is independent on the 3N interaction. To verify this assumption, it is necessary to obtain data for various energies.
The advantage of RADEX channel of the Moscow Meson Factory (INR RAS) is a possibility of studying nd-breakup reaction in a wide range of neutron energies. Although the energy spectrum of neutrons formed in the beamstop of INR linear proton accelerator is wide and includes all energies up to the limit ones equal to the energy of the proton beam, the energy of the primary neutron may be reconstructed from the kinematics of the reaction and, thus, the data may be obtained in a wide range of primary energies.
In [2], data on nn-scattering length were obtained in nd-breakup reaction at energy of 60 MeV. In this work, the reaction was studied both at low energy ~ 10 MeV and at high one ~ 80 MeV. Two neutrons were detected in the kinematic region of FSI at neutron opening angle of $\Delta$Θ = 5°. The proton was detected in the active C$_{6}$D$_{6}$ scintillator target. The energies of secondary neutrons were determined by the time of flight, and the relative energy of the nn-pair was calculated for each event using the energies of two neutrons and their opening angle.
In this experimental setup, the neutron-neutron interaction in the final state manifests as a maximum in the dependence of reaction yield on the relative energy of two neutrons, the shape of which is sensitive to the scattering length $a_{nn}$. To determine $a_{nn}$, the experimental dependence of nd-breakup reaction yield was compared with the simulation results.
Earlier in [1], it was suggested that the reason of discrepancies in experimental $a_{nn}$ values (from –16 to –22 fm) may be connected to a large effect of $3N$ forces. It can also be assumed that the values of the proton-proton scattering length $a_{pp}$ and the energy of the virtual $^{1}S_{0}$ state $E_{pp}$ extracted from the experiment with three particles in the final state will differ from the values obtained in the free $pp$ scattering. We plan to test this idea studying the $d+^{1}$H$→p+p+n$ reaction.
Simulation of this reaction showed that studying the energy spectrum shape of single proton in coincidence with the neutron will allow us to determine the energy of the virtual state of the $pp$-pair. Parameters of the experimental setup were also determined by simulation.
The experiment was started at 15 MeV deuteron beam of the SINP. A solid deuterated polyethylene target was used. To determine the spectrum of protons, we used a three-detector ($\Delta E-E_{1}-E_{2}$) telescope of silicon surface-barrier detectors. The advantage of such a system is a separation of events with coincidences in two ($\Delta E-E_{1}$) and three ($\Delta E-E_{1}-E_{2}$) telescope detectors, which greatly simplifies the analysis of energy loss diagrams (the absence of inverse loci in $\Delta E-E_{1}$ and $E_{1}-E_{2}$ diagrams). With this in mind, a technique was developed for reconstructing the energy spectrum of charged particles from energy losses of particles in detectors. The basis of this technique is the kinematical simulation of the passage of charged particles through matter. The neutron energy is determined by the time of flight using liquid-hydrogen scintillation detector. At that, it is possible to separate neutron events from those caused by gamma rays by the pulse shape. Preliminary data on the shape of the spectrum of protons in coincidence with neutrons are obtained.
The results on the vector Ay and
tensor Ayy and Axx analyzing powers in deuteron-proton
elastic scattering at large transverse momenta are presented.
These data were obtained at internal target at JINR Nuclotron
in the energy range 400-1800 MeV using polarized deuteron beam
from new polarized ion source.
New data on the deuteron analyzing powers in
in the wide energy range demonstrate the sensitivity to the short-range spin structure
of the isoscalar nucleon-nucleon correlations.
Nitin Sharma and Manoj K. Sharma
School of Physics and Materials Science, Thapar Institute of Engineering & Technology,
Patiala-147004, India
E-mail: msharma@thapar.edu
The study of heavy ion induced reactions provides an opportunity to extract the knowledge of nuclear dynamics and related structural effects of nuclear systems belonging to different regimes of isotopic chart. Significant theoretical and experimental work have been done to understand the dynamical processes associated with variety of nuclear reactions, but still there is an enigma among the investigators due to complex nuclear properties and associated aspects. In view of this, the present work aims to analyse the decay of 221Ac* nucleus formed in 16O+205Tl reaction at Ec.m.=76.2-104.5 MeV. In reference to the experimental finding of Gehlot et al. [1], the evaporation residue (ER) cross sections are calculated using Dynamical Cluster decay Model (DCM) [2,3]. The corresponding decay properties are investigated by analysing the fragmentation potential and preformation probability of decaying fragments. Note that, the calculations are performed using quadrupole(ß2) deformations of decay fragments with optimum orientations (θiopt ). We intent to present comprehensive analysis of decay dynamics associated with the chosen reaction at time of conference.
[1] J. Gehlot, A.M. V. Kumar et al.// Phys. Rev. C. 2019. V. 99.I.034615.
[2] A. Kaur, M. K. Sharma//Phys. Rev. C. 2019. V. 99.I.044611
[3] N. Grover, K. Sandhu, M. K. Sharma//Nucl. Phys. A. 2018.V.974.P.56.
In the analysis of heavy-ion fusion cross-sections, the relativistic effects are usually ignored [1]. However, it is known that the fastest nucleons in a nucleus have the velocity close to a quarter of the speed of light. The relativistic mean-field (RMF) theory accounting for the effects of high nucleons velocity was successfully applied to reproduce the binding energies and astrophysical S-factors for proton-induced reactions [2].
In the present work, we demonstrate the results of the application of the RMF theory for describing the heavy-ion above-barrier fusion process of complex nuclei. The modeling is performed within the framework of a trajectory model [3-5] based on the double-folding approach and accounting for energy dissipation. We employ six different RMF parameter sets for the effective nucleon-nucleon (NN) forces. The forces as well as the resulting potentials and cross-sections are compared with those obtained using the non-relativistic M3Y NN-forces.
It turned out that several of the RMF parameter sets appeared to be inapplicable for the dynamical calculations of the fusion cross-sections. For the feasible parameter sets, we perform a quantitative comparison of the calculated above-barrier fusion excitation functions with the experimental ones for reactions involving spherical colliding nuclei.
1. Newton et al. // Phys. Rev. C 70 (2004) 024605.
2. Lahiri et al. // Int. J. Mod. Phys. E 25 (2016) 1650015.
3. Gontchar et al. // Phys. Rev. C 89 (2014) 034601.
4. Chushnyakova et al. // Phys. Rev. C 90 (2014) 017603.
5. Chushnyakova et al. // Nucl. Phys. A 997 (2020) 121657.
Today the studies of the hadron yields containing heavy quarks are of particular interest for high-energy physics. These yields are characterized by small cross-sections for interaction with the nuclear medium. As a result, for the processes of relativistic nuclear collisions the information about the states of nuclear matter (arising in such processes) could be obtained. In this case, the efficient identification of strange and charmed particles registered by the experimental setup plays an important role in the analysis of possible phase transitions. In addition, at the energies of the colliding nuclei which are accelerated in Nuclotron-based Ion Collider fAcility (NICA) [1], it is possible to study clusters of dense nuclear matter arising inside the nuclei. Therefore, for precise registration of short-lived particles produced in nucleus-nucleus collisions the Vertex detector based on silicon monolithic active pixel detectors (as a part of the Multi-Purpose Detector (MPD) experiment) was proposed.
In present overview the properties of silicon monolithic active pixel detectors (developed for the upgraded Inner Tracing System of ALICE experiment in CERN [2]) together with new ultralight, radiation-transparent carbon fiber support structures as basic elements for Vertex detector of MPD experiment will be discussed. To investigate the tracking efficiency and main characteristics of the silicon pixel detectors, the comprehensive studies with a variety of gamma, beta sources and also with cosmic rays were carried out.
Acknowledgments: the reported study was supported by RFBR, research project No. 18-02-40075.
[1] V.Kekelidze, V.Matveev, I.Meshkov, A.Sorin, G.Trubnikov, Project Nuclotron-based Ion Collider Facility at JINR. Physics of Particles and Nuclei, 2017, Vol. 48, No. 5, pp. 727–741.
[2] ALICE collaboration, Technical design report for the upgrade of the ALICE Inner Tracking System, Journal of Physics G: Nuclear and Particle Physics, vol. 41, iss. 8, P087002, 2014.
After BM@N technical run in spring 2018, the first physical stage of the experiment will begin in 2021. For stop time Silicon tracking modules of BM@N Forward Silicon Detector are applied at muon stand to test and measure R-t characteristics of straw detectors (6 mm diameter, produced by JINR, Dubna) by reconstructing cosmic rays tracks (based on bmnroot software). Muon stand consists of Triggering scintillators, Silicon tracking planes, Straw detectors and Data Acquisition System. Si modules based on Double-sided Silicon Strip Detectors (DSSDs, pitch 95 μm p+ side and 103 μm n+ side, stereo angle between strips is 2.5o) are used as external tracking system in muon stand. General view of stand, Si-modules description and first measurement results are presented.
The BM@N is a fixed target experiment for studies of baryonic matter at the Nuclotron (JINR, Dubna). According to upgrade plans for BM@N, vacuum beam pipe will be added into experimental setup. To determine the coordinates of incident “trigger ion” and to tune the beam, it is necessary to develop three coordinate stations of beam tracker and two coordinate stations of beam profilometer respectively. Each station of beam tracker or beam profilometer will be based on Double-sided Silicon Strip Detector (DSSD) with 175 μm thickness and following number of strips: 128x128 is for tracker and 32x32 – profilometer. Front-end electronics for these Silicon Detectors are based on the multichannel IDEAS (Integrated Detector Electronics AS, Norway) ASICs. Overview of developing system is presented.
BM@N (Baryonic Matter at Nuclotron) is the first experiment to be realized at the accelerator complex of NICA-Nuclotron at JINR (Dubna). The aim of the experiment is to study interactions of relativistic heavy ion beams with a kinetic energy from 1 to 4.5 AGeV with fixed targets.
In the report an algorithm for global tracks reconstruction in the BM@N experiment are described. The core of the global track is the track inside the magnet, to which are added upstream and downstream tracks.
The results of the proposed algorithm working for both the BM@N experiment and its extension SRC program are presented. Matching efficiency and residuals are shown. Influence of global matching procedure on quality of momentum reconstruction and other parameters of a track are presented.
BM@N experiment of the NICA accelerator complex at the Joint Institute for Nuclear Research, Dubna is aimed at studying heavy ion collisions with fixed targets. The BmnRoot software package [1, 2] is used in the BM@N experiment and it plays a crucial role both in event simulations and in track and event reconstruction [3]. Event reconstruction may take significant time per event. Time of reconstruction depends on the kind of the colliding particles, the beam energy, the collision centrality and other parameters. Event simulations with realistic Monte-Carlo generators are also time-consuming. Processing of big amount of data which is produced in physical runs of the accelerator takes significant time, so the software performance should be optimized to make the data processing efficient [4].
We have performed high-performance optimization of the simulation and reconstruction modules of the BmnRoot software package. The optimization is based on the performance analysis [5] of the BmnRoot package on representative test cases and on localization of the performance bottlenecks in the software source code. Several approaches have been tested and the most suitable approaches to the BmnRoot optimization are chosen. Parallelization of some modules has been performed. Numerical estimates of the scalability and speedup of the parallelized modules for event simulation and reconstruction demonstrate good efficiency of parallelization.
Other approaches to high-performance optimization such as adaptation of the BmnRoot software package for hybrid computing systems, its vectorization and algorithmic optimization are also considered.
The reported study was funded by RFBR according to the research project № 18-02-00041.
References
BM@N experiment at Nuсlotron in Dubna is currently being upgraded for the study of dense nuclear matter in heavy-ion collisions. One of the major upgrades is a new hybrid tracking system consisting of large-area Silicon Tracking System (STS) with fast data-driven readout to be installed in-front of seven GEM planes currently partially installed. The STS contains of four position-sensitive stations built of modules with double-sided microstrip silicon sensors which have been developed for the CBM experiment at FAIR. STS consumes 292 silicon modules the assembly of which is making a challenge. For this task a working group in VB LHEP JINR developed customized methods to be briefly reported along with the workflow description and first results.
In order to study the high-density nuclear equation-of-state in collisions between gold nuclei at Nuclotron beam energies (2– 4.5A GeV), the existing BM@N experiment at JINR in Dubna has to be substantially upgraded. The measurement of high-multiplicity events at interaction rates up to 5 MHz requires the installation of four new tracking stations equipped with double-sided micro-strip silicon sensors, which have been developed for the CBM experiment at FAIR. It has been demonstrated by simulations that the hybrid tracking system comprising four silicon stations and seven (already partly existing) GEM tracking detectors will be able to reconstruct charged particles including hyperons emitted in Au+Au collisions with good efficiency and high signal-to-background ratio. The results of the simulations and the status of the detector development are presented.
Work is supported by RFBR 18-02-40047 grant.
Today the silicon-based detector systems are playing a key role in experimental studies of the nuclear matter properties. Using thin silicon pixel detectors for the precise identification of charged particles opens completely new opportunities to investigate the states of nuclear matter arising in processes of relativistic nuclear collisions. For stable operational conditions of such detectors, the efficient mechanic and cooling systems at minimum material budget should be used.
In present work, the ideas and developments for mechanic and cooling systems for novel vertex detectors based on silicon pixel sensors have been presented.
The reported study was supported by RFBR, research project No. 18-02-40075.
A method is proposed [1] for constructing a model for the interaction of fields of quantum electrodynamics (QED) with two-dimensional materials in the framework of the Symanzik approach [2]. It is based on the modification of the QED Lagrangian by adding to it an additional contribution (the Lagrangian of the defect) concentrated in a two-dimensional region of space. The requirement to comply with the basic principles of QED (renormalization, locality, gauge invariance) makes significant restrictions on the type of defect Lagrangian. As a result of the modification of QED, a small number of new dimensionless parameters appear in the model which describe the material properties of defect. The Dirac spinor fields in this approach can be used to describe the processes of interaction of spin ½ particles (electrons, protons, neutrons) with two-dimensional objects. The talk presents the results of the study of the scattering of Dirac particles on a homogeneous isotropic plane, as well as properties of bound states arising from the interaction of the spinor field with the plane [3-8]. It is shown that the choice of specific values of the seven dimensionless parameters in the model can achieve significant differences in the quantitative characteristics of the studied physical effects. Theoretical investigations within the framework of the proposed approach may be useful both for improving the methodology of experiments with two-dimensional materials, and for analyzing the possibilities of technical devices created on their basis.
References
[1] V.N. Markov, Yu.M. Pis'mak, Casimir effect for thin films in QED // Journal of Physics A: Mathematical and General, 2006. --Vol. 39,-- P. 6525-6532; arXiv: hep-th/0505218v3, 2005; D.Yu. Pis'mak, Yu.M. Pis'mak, Modeling the interaction of a material plane with a spinor field in the framework of Symanzik's approach // Theoretical and Mathematical Physics, 2015. --Vol.184,--№ 3.-- P. 505–519.
[2] K. Symanzik, Schrödinger representation and Casimir effect in renormalizable
quantum field theory//Nucl.Phys. B, 1981-- Vol. 190, P. 1-44.
[3] Yu.M. Pismak, O.Yu. Shakhova, Symanzik approach in modeling the interaction of quantum fields with extended objects: scattering of Dirac particles on material plane// Phys. Part. Nucl. Lett., 2019 – Vol. 16, – P. 441-444.
[4] Yu.M. Pismak, Modelling of Bound States of Dirac Particles in Singular Background in Framework of Symanzik Approach. // Phys. Part. Nucl. Lett. , 2018— Vol. 15, 4, —P. 380-383.
[5] Yu. Pismak, F. Wegner, Dispersion relations and dynamic characteristics of bound states in the model of a Dirac field interacting with a material plane //EPJ Web of Conferences, 2018 —Vol. 191, — P. 06015.
[6] Yu.M. Pismak and D.Yu. Shukhobodskaia Symanzik approach in modeling of bound states of Dirac particle in singular background // EPJ Web of Conferences, 2017. — Vol. 158, — P. 07005.
[7] Yu.M. Pismak and D.Yu. Shukhobodskaia, Bound states in a model of interaction of Dirac field with material plane // EPJ Web of Conferences, 2016. — Vol. 125, — P. 0522.
[8] Yu.M. Pis'mak, D.Yu. Shukhobodskaia, Model of Dirac field interacting with material plane within Symanzik’s approach, // EPJ Web of Conferences, 2016. — Vol. 126, — P. 05012.
The description of relativistic nuclear interactions in the four velocity space allows to enter the self-similarity parameter. This parameter allows us to describe rather well the ratio of the proton to anti-proton yields in A-A collisions as a function of the energy in a wide range from 10-20 GeV to a few TeV. It is shown that the inclusive spectra of the produced hadrons in hadron-hadron and nuclear-nuclear collisions can be presented as the universal function dependent of the self-similarity parameter in analytical form. The experimental data are in good agreement with results our calculations in a wide energy range from a few GeV to a few TeV in central rapidity region.
The study of continuous (Lorentz transformations) and discrete symmetries of P, T, C, CP, and CPT and their disturbances is one of the important directions in modern quantum field physics. However, the derivation of formulas defining these transformations for spinors still relies heavily on physical considerations, rather than on the algebraic properties of spinors. Initially, in quantum field theory, spinors were considered using the Dirac matrix formalism. The modern theory of spinors is formulated in the framework of the formalism of Clifford algebras, such spinors are called algebraic [1]. However, algebraic spinors are rarely used in quantum field theory, since difficulties arise in constructing the vacuum state vector, second quantization theory, and spinor bundles. The theory of superalgebraic spinors [2-4], which is an extension of the theory of algebraic spinors, solves these problems. In it, spinors, basis Clifford vectors (analogues of Dirac gamma-matrices) and the state vector of vacuum are constructed from Grassmann variables and derivatives with respect to them. In this case, the expansion of the second quantization for the operator of the spinor field is obtained from purely algebraic relations, and the spinor momentum, electromagnetic and other gauge fields are of the same nature - they arise as affine connections in a superalgebra bundle. In the case of four independent Grassmann variables and derivatives with respect to them, not five Dirac matrices arise, but seven gamma operators - superalgebraic analogues of such matrices. Of these, one corresponds to the fifth Dirac matrix, multiplied by an imaginary unit, and is a pseudovector.
We have shown that in a matrix formalism there are two outwardly indistinguishable, but fundamentally different types of matrix operators acting on spinors. Operators of the first type are associated with spinor transformations. The operators of the second type are associated with the replacement of the spinor basis, and in the superalgebraic formalism, the spinor itself does not change from such a replacement.
We have constructed in an explicit form the state vector of the vacuum and its change during symmetry transformations. It is invariant with respect to Lorentz transformations and spatial reflections. There are two unitary transformations of the reflection of the time axis, which act equally on Clifford vectors, but act differently on spinors. For one of them, the vacuum is not T-invariant. When the time axis is reflected, it passes into an alternative vacuum, for which the spinor creation operators turn into annihilation operators, and the annihilation operators turn into birth operators. For the second operator, the vacuum is T-invariant, and the corresponding CPT transformation is an anti-unitary symmetry transformation.
$\bf{A.T. D’yachenko^{1,2}}$
$^{1}$Emperor Alexander I Petersburg State Transport University, St.Petersburg, Russia;
$^{2}$NRC "Kurchatov Institute", Petersburg Nuclear Physics Institute, Gatchina, Russia
The transverse momentum distributions for lambda-hyperons are found in the thermodynamic model, which are in agreement with experimental data for proton-proton collisions with energies of $\sqrt{s}$ = 53, 200, 900, and 7000 GeV. The calculated spectra are consistent with the results of the quark-gluon string model [1].
The spectra of soft photons in proton-proton collisions were also considered in the thermodynamic approach at a proton momentum of 450 GeV /c on a fixed target [2], and the possibility of an exess in this experiment for a new particle, X17 boson with a mass of 17 MeV [3,4], was analyzed.
$\bf{References}$
1. O. Piskounova, arXiv: 1908.10759v3 [hep-ph].
2. A. Belogianni et al., Phys. Lett. $\bf{B 548}$, 129 (2002).
3. A.J. Krasznshorkay at al, Phys. Rev. Lett. $\bf{116}$, 042501 (2016).
4. C.Y. Wong, arXiv: 2001.04864v1 [nucl-th]
The holographic methods inspired by the gauge/gravity correspondence
from string theory have been actively applied to the hadron spectroscopy in
the last fifteen years. Within the phenomenological bottom–up approach,
the linear Regge-like trajectories for light mesons are naturally reproduced
in the so-called “soft-wall” holographic models. I will give a very short
review of the underlying ideas and technical aspects related to the meson
spectroscopy.
The AdS/QCD models are believed to interpolate between low and high energy sectors of QCD. This claim is usually based on observations that many phenomenologically reasonable predictions follow from bounds imposed at high energies although the hypothetical range of applicability of semiclassical bottom-up holographic models is restricted by the gauge/gravity duality to low energies where QCD is strongly coupled. To test the feasibility of high energy constraints it is interesting to calculate holographically several observable constants at low and high momenta independently and compare. We will discuss an AdS/QCD model which describes the Regge-like linear spectrum of spin-1 mesons in a general form and demonstrate that under certain physical assumptions the low-energy constraints on 2-point correlation functions lead to nearly the same numerical values for the parameters of linear radial spectrum as the high energy ones. This coincidence looks surprising in view of the fact that such a property for observables is natural for conformal theories while real strong interactions are not conformal.
Based on: arXiv:2006.14439
The modern medical method of nuclear visualization based on monoclonal antibodies, the new carriers of the radioactive label, is Immuno-PET. For its realization, it is necessary that the biological half-life of the molecule, the label carrier, coincides with the half-life of the radioactive isotope. The $^{89}$Zr isotope has optimal physical characteristics for Immuno-PET: it decays with a half-life of 78.41 hours by positron emission and electron capture to the intermediate state $^{89m}$Y, which decays to stable $^{89}$Y with half-life 15.7 s.
Traditionally, $^{89}$Zr is produced with cyclotrons in the ($p, n$)- and ($d$, 2$n$)-reactions. However, in both methods, the exclusion of $^{88}$Zr isotope impurities with a half-life of 83.4 days and its daughter $^{88}$Y isotope with a half-life of 106 days resulting from ($p$, 2$n$)- or ($d$, 3$n$)-reactions presents a significant problem.
Therefore, an urgent task is to study the $^{89}$Zr yield in various photonuclear reactions.
We irradiated a $^{94}$Mo enriched molybdenum target and a tantalum monitor target using an electron accelerator with a 20 MeV maximum electron energy.
The spectra of irradiated targets were measured by Canberra and Ortec gamma spectrometers with ultra-pure semiconductor detectors with a (15–40)% detection efficiency compared to a 3′×3″ NaI(Tl) detector. The energy resolution of the spectrometers was 1.8–2.0 keV on the 1332 keV $^{60}$Co γ-line. In the studied spectrum, γ-transitions from $^{89}$Zr decay are reliably identified. The bremsstrahlung spectrum was simulated using the Geant4 software code.
As a result, we obtained the integral cross-section for the $^{94}$Mo(γ, $n$)$^{89}$Zr reaction equal 4.5 mbn×MeV. The $^{89}$Zr yield is 5×10$^4$ Bq×μA×hour. Obtained data are discussed.
The beam hardening effect can induce strong artifacts in CT images, which leads to severe deterioration in image quality. This work develops an effective beam hardening correction algorithm using filtered back-projection based maximum a posteriori.
An x-ray tube emits a continuous spectrum, which gives rise to energy-dependent attenuation of different tissues. The spectrum is not known with sufficient accuracy as a rule/ Low-energy photons are preferentially absorbed compared to photons with higher energy along the integral path of a polychromatic x-ray beam, such that the beam gradually becomes harder, i.e. its mean energy increases. Neglecting this beam hardening effect in reconstruction leads to artifacts.
The iterative approaches that suppress beam hardening induced artifacts by directly incorporating the beam hardening effect into the projection matrix in an iterative reconstruction model were proposed earlier in [1]. The proposed method can be considered as an iterative maximum a posteriori reconstruction with the beam hardening effect incorporated in the forward-projection.
The algorithm has important properties. Most other iterative approaches require prior knowledge of the energy spectrum or the material composition, which is difficult to obtain in some clinical practice cases. The proposed method does not suffer from this obstacle, and can be used when no information about the beam spectrum or the material properties is available. It based on a fact that attenuation in every voxel can be decomposed into a photoelectric component and Compton scatter component. Besides, the photoelectric component depends on atomic number very strong: total cross section is proportional to $Z^{4.5}$ and its maximum value is shifting to the more energies when $Z$ increase. In our method, we use the database for energy dependence of the photoelectric cross section for the different materials that might induce “hardening” artifacts, such as bone, aluminum and titanium implants etc.
This method has a high computation efficiency and needs small amount of iterations to obtain a satisfying reconstruction result. With usage of high voltage or bow-tie wedges to reduce the amount of low energy photons, the iteration number can be further reduced. In addition, the proposed method performs well in terms of both the overall reconstruction quality and suppression of beam hardening induced artifacts.
Currently, photon beams obtained from linear electron accelerators are used for radiation therapy. The most widely used bremsstrahlung is ones with a maximum energy of 6, 10, 15, 18, and 20 MeV. The main advantages of radiation therapy with high-energy photons (15, 18 and 20 MeV) are high penetrating ability, the ability to create a maximum dose at almost any depth of the tumor in the patient’s body, a reduced dose for the skin and a reduced peripheral dose due to lower angular dispersion. However, the interaction of photons with an energy of more than 8 MeV with the structural elements of the accelerator made of materials with a high atomic number is accompanied by the formation of secondary neutron radiation through (γ, $Xn$) reactions, subsequent neutron capture is a source of induced gamma radioactivity, which does not generate a dose taken into account in radiotherapeutic treatment.
The neutron flux intensity of the Varian Trilogy linear medical accelerator with a maximum electron energy of 20 MeV was estimated by the activation method by irradiating tantalum targets with brake beams under conditions close to clinical. Because fast neutrons make the main contribution to the patient’s dose, the targets were irradiated as part of the tantalum – cadmium – tantalum – cadmium foil assembly to cut off thermal neutrons.
The spectra of irradiated targets were measured by Canberra and Ortec gamma spectrometers with ultra-pure semiconductor detectors with a (15–40)% detection efficiency compared to a 3′×3″ NaI(Tl) detector. The energy resolution of the spectrometers was 1.8–2.0 keV on the 1332 keV $^{60}$Co γ-line.
The gamma transitions from the $^{180}$Ta formed in the $^{180}$Ta(γ, $n$)$^{181}$Ta reaction and $^{182}$Ta formed in the $^{181}$Ta($n$, γ)$^{182}$Ta reaction were reliably distinguished in the studied spectra.
The average fast neutron energy was calculated from the reconstructed spectrum obtained by a modified Bonner activation spectrometer. The energy distribution of the secondary neutron flux density in the neutron energy range 0.1–15 MeV were obtained by the SDMF-1608PRO spectrometer-dosimeter. After analyzing the spectra, it was found that the average fast neutron energy of the Varian Trilogy linear medical accelerator is 0.89±0.02 MeV. Experimental data of neutron energy and activation of tantalum monitor targets were used to estimate the fast neutron flux. It was found that the flux of fast neutrons on the tantalum monitor target is from 5 to 10% during the accelerator operates with a 20 MeV bremsstrahlung maximum energy.
Taking into account the coefficient of relative biological efficiency of neutron radiation for neutrons with energies from 100 keV to 2 MeV, equal to 20, compared with the coefficient for gamma rays (equal to 1), even in preliminary studies, there is a significant underestimation of the contribution radiation of secondary neutrons in the total dose received by the patient during radiation therapy with 20 MeV bremsstrahlung maximum energy.
A discussion of the findings is ongoing. The reported study was funded by RFBR according to the research project №18-00-00745.
The main goal of the FOOT experiment is to provide nuclear cross section measurements necessary in two different fields: hadrontherapy and radioprotection in space.
In the last decade, a continuous increase in the number of cancer patients treated with Particle Therapy (PT) has been registered, due to its effectiveness in the treatment of deep-seated solid tumors [1]. When the charged particles travel through the patient, nuclear interactions occur producing nuclear fragments that can cause side effects in regions outside the tumor volume. Nuclear fragmentation produces both light and heavy fragments: the first are produced within a wide opening angle, while the second close to the beam direction. To detect both types of fragments, the FOOT detector consists of two different configurations: an electronic setup [2] and an emulsion chamber [3].
Target (16O,12C) fragmentation induced by 150-250 MeV proton beam will be studied via inverse kinematic approach, where 16O and 12C beams, in the 150-200 MeV energy range, collide on graphite and hydrocarbons target to allow the extraction of the cross section on Hydrogen. This configuration explores also the projectile fragmentation of these beams. The electronic setup includes a pre-target region (a plastic scintillator and a drift chamber), a magnetic spectrometer based on silicon pixel and strip detectors, a scintillating crystal calorimeter able to stop the heavier fragments produced and to achieve the needed energy resolution, and finally a TOF and ΔE scintillating detector for particle identification. The emulsion chamber setup includes the same pre-target region as the electronic setup and a set of three different emulsion chambers for different purposes.
Regarding to the second FOOT mission, the XXI century will be characterized by a deeper exploration of the Solar System that will involve long term missions as the expedition to Mars. Health risks are associated to exposure to Galactic Cosmic Radiation (GCR), that is very energetic (on average around 700-1000 MeV/u) and produces showers of light fragments and neutrons by nuclear fragmentation when hitting the spaceship shields. Considering that the GCR are composed of 90% of protons, 9% of helium and the rest of heavy nuclei, the overlap with the measurements for hadrontherapy purposes is large, the main difference being the energy range.
The experiment is being planned as a ‘table-top’ experiment in order to cope with the small dimensions of the experimental halls of the CNAO, LNS, GSI and HIT treatment centers, where the data taking is foreseen in the near future (2020). The detector, the performances, the physical program and the timetable of the experiment will be presented.
References
[1] M. Durante and J. Loeffler, Charged particles in radiation oncology, Nature Reviews Clinical Oncology, 7:37-43, 2010;
[2] G. Battistoni et al, The FOOT (FragmentatiOn Of Target) experiment, Proceedings of Science, 302, 2017;
[3] G. De Lellis et al, Emulsion cloud chamber technique to measure the fragmentation of a high-energy carbon beam, Journal of Instrumentation, 2, 2007.
As it has been demonstrated by the conducted experiments, the production of targeted radioactive pharmaceutical preparations (RPHs) that are based on alpha-emitters using the traditional approach (biologically active molecular constructs with a chelate, DOTA, that carries a radioactive tracer) is just a sort of scientific mystification: the recoil nuclei formed after such decay will destroy the carrier molecules thus completely excluding a targeted transport of the preparation.
A success in the production of such pharmaceutical formulations that are based on the use of alpha-emitters is possible only in the case when there is some way of “levelling” the harmful effect of recoiling nuclei, for example, by means of using inorganic compounds (“nano-containers”) of a high radiation resistance.
As such a model matrix material, magnetite, Fe3O4, has been used whose main transport characteristic that accounts for the transportation accuracy of magnetite-based RPHs is the value of the internal magnetic field on the iron nuclei. The magnetite nano-crystallites have been prepared labelled with Auger- and internal conversion electrons, beta- and alpha-emitters (57Co, 60Co and 241Am radionuclides).
A comparative analysis has been conducted of radiation-induced damage patterns in nano-crystallites in the dependence of nuclear- and physical characteristics of the radioactive tracer and total fluence. It has been established that under irradiation there is a comminution of crystallites taking place, the effective magnetic fields on the iron atoms in the labelled nano-crystallites remaining unchanged irrespective of the “dose load”.
Taking into consideration the typical recoil energies (90 keV to 150 keV) of the daughter atoms that are produced as a result of alpha-decay, the chemical composition and density of possible “carriers” needed for an efficient “conservation” of traditional therapeutic radionuclides (in particular, 211At, 212Bi, 213Bi, and 223Ra), “nano-containers” should be used with the particle size of not less than 80 nm.
The work was supported by a grant from the Russian Foundation for Basic Research (18-03-00832).
Radioisotopes of 227Ac and 227,228,229Th are basis of the radiochemical generators for production of alpha-emitters radium-223, radium-224, actinium-225 and bismuth-213. These generator radionuclides are used to produce radiopharmaceuticals and therefore their radiochemical purity has to be maintained high demands. For example, actinium-225 generator has to contain less than 1·10-3 % of each Ra and Th isotopes (standard of ORNL), radium-223 generator – less than 0.5% of thorium-227 and 0.04% of actinium-227.
Irradiated radium-226 used in the presented work is contained mixture of all abovementioned isotopes with their daughter radionuclides. In frame of the presented work methods of chromatographic extraction [1] of thorium-229 and actinium-227 from irradiated radium-226 have been developed and tested with technological reprocessing procedures [2]. Activities of 226Ra, 227Ac, 227,229Th and their daughter nuclides for chemical procedures and final batches have been measured with gamma- and alpha-spectrometry. Measured activities of 227Ac and 227,229Th were compared with values calculated by a computer code.
Taking into account the effect of Gd self-shielding in experiments with Magnevist on Gd NСT significantly improves the accuracy of determining the absorbed dose. As is known, collimated neutron beams are mainly used in NСT, therefore, the bulk of thermal neutrons fall from the front side and, at a high concentration of gadolinium, are absorbed by the front layers of gadolinium. In work [1], the effect of self-shielding was confirmed by calculations using MSNP for modeling and when measuring the dose of gadolinium using chemical Frice dosimeters. The effect of self-shielding when using a drugs based on 10B and B4C was also investigated in works [2,3]. It is especially important to consider this effect when conducting radiobiological experiments, since excess concentration of gadolinium can lead to an underestimation of the expected dose in the tumor or to the irregularity of its exposure. In this paper, we present the results of calculations of the MCNP simulation of experiments on epithermal neutron irradiation of biopsy samples of human brain glioma tumors. Using these calculations, we performed experiments on tissue samples of human glioma tumors extracted during surgery. From tissue samples of tumors, live sections were prepared and placed in a nutrient medium. Prepared live sections were used to irradiate a beam of epithermal neutrons in the presence of the Magnevist preparation. The dependence of the percentage of necrosis in the samples on the concentration of Gd in human brain glioma tumors was studied experimentally The results showed that the percentage of necrosis in the tissues of human brain tumors linearly depends on the concentration of Gd to 1000 ppm, and with a further increase in the concentration, the percentage of necrosis does not change. This indicates that, due to the above factors, there is a certain optimal concentration of Gd for irradiating human brain glioma tumors, and a further increase in the concentration of Gd can adversely affect, i.e. reduces the absorbed dose. This fact must be taken into account when using various drugs to increase the effectiveness of GdNСT.
The nuclear physics methods are increasingly important in medicine for the early diagnosis of diseases. Nuclear medicine is of the most modern methods of non-invasive functional diagnostics, providing information that cannot be acquired with other imaging technologies. Its methods require advanced mathematics for data processing and analysis [1]. Development of mathematical methods and data processing software for single photon emission computed tomography (SPECT) and positron emission tomography (PET) remains challenging problem.
The report discusses the methods for radionuclide image processing for dynamic and gated SPECT data [2]. There is a trend toward complete automation of processing and interpretation of radionuclide studies. The report presents the developed data processing software suite for nuclear medicine imaging. In conclusion, the main directions and prospects for the development of nuclear medicine data processing tools are considered.
REFERENCES
1. E.Kotina, A.Babin, P.Bazhanov, D.Ovsyannikov, V.Ploskikh, A.Shirokolobov. Mathematical and Computer Methods of Data Processing in Nuclear Medicine Studies. Proceedings of RuPAC2016. 2017. pp. 480-482.
2. V.Ploskikh, E.Kotina. Quantitative analysis of gated myocardial perfusion SPECT. Cybernetics and physics, 2018. 7(4):220–227.
The wave functions of the ground states of few-body nuclei ${}^{10,11}$B, ${}^{10,11}$C were calculated by Feynman’s continual integrals method in Euclidean time [1–3]. The algorithm of parallel calculations was implemented in C++ programming language using NVIDIA CUDA technology [4]. Calculations were performed on the NVIDIA Tesla K40 accelerator installed within the heterogeneous cluster of the Laboratory of Information Technologies, Joint Institute for Nuclear Research, Dubna.
The studied isotopes are considered as cluster nuclei with the following configurations: ${}^{10}$B ($2\alpha$ + n + p), ${}^{11}$B ($2\alpha$ + n + n + p), ${}^{10}$C ($2\alpha$ + p + p) and ${}^{11}$C ($2\alpha$ + n + p + p). Results of the cluster model were compared with results of the shell model of deformed nuclei [5, 6].
References
1. R.P.Feynman and A.R.Hibbs. Quantum Mechanics and Path Integrals (McGraw-Hill, New York, 1965).
2. E.V.Shuryak and O.V.Zhirov // Nucl. Phys. B. 1984. V.242. P.393.
3. V.V.Samarin, M.A.Naumenko // Phys. Atom. Nucl. 2017. V.80. P.877.
4. M.A.Naumenko and V.V.Samarin // Supercomp. Front. Innov. 2016. V.3. P.80.
5. V.V.Samarin // Phys. Atom. Nucl. 2010. V.73. P. 1416.
6. V.V.Samarin // Phys. Atom. Nucl. 2015. V.78. P. 128.
An application of Glauber theory of multiple scattering to calculation of differential cross sections and polarizing characteristics of particles scattering on light nuclei took an important place in research activity of E.T.Ibraeva. All calculations were carried out in the framework of reliable spectroscopic approach to nuclear reactions. Its essence is in use of nuclear models reproducing practically all spectroscopic characteristics of the nuclei under consideration. Three-particle models of $^6$Li and $^9$Be nuclei developed in MSU are related to that; as well as a multiparticle shell model for nuclei with $A =$ 6 – 14 and particle-hole shell model with $A =$ 15; a three-particle model of $^8$Li and $^9$Li nuclei and two-particle $\alpha t$-model for $^7$Li nucleus suggested in KazNU and etc. As our experience shows when realizing the spectroscopic approach, if the dominating mechanism of process is known, one can obtain not only a description of the main characteristics of the process but can also rely on the predictive character of the theory.
The particular role is for direct evidence of the halo-structure of the low-lying excited states of $^9$Be nucleus with quantum numbers $1/2^+$ and $3/2^+$ obtained by the authors lately [1]. In the framework of $\alpha \alpha n$-model of $^9$Be nucleus it was shown that the valence neutron is located with a large probability at a distance of 11 $fm$ from the center of mass of two $\alpha$-particles, at the same time this distance is several times smaller in the ground $3/2^–$ state.
In the present work the results obtained are supported by calculations of the structure of low-lying $5/2^+$ and $5/2^–$ levels. This allows concluding generally: levels of negative parity in $^9$Be nucleus, in which the valence neutron is in $p$-state, do not have a halo-structure; at the same time the low-lying levels of positive parity do have it.
Conclusions about structure of the low-lying levels of $^9$Be nucleus, obtained on the base of $\alpha \alpha n$-model, are supported with calculations of $p^9$Be-scattering: an account of halo-structure only allows reproducing experimental data on inelastic scattering on levels of positive parity [2].
Properties of ultramagnetized atomic nuclei relevant for supernovae, neutron star mergers, magnetar crusts and heavy-ion collisions are analyzed. Nuclear magnetic reactivity of Zeeman type is shown to dominate for field strengths below ten teratesla. Respective linear magnetic response is given as a combined reactivity of valent (outer shell) nucleons and can be described in terms of nuclear magnetic susceptibility. Valent protons and neutrons occupy [1] orbitals with minimum and maximum spin projection on a field axis, respectively. Consequently, charged (protons) and neutral (neutrons) nucleons are spatially separated. Effects of such charge dipole polarization in nuclear reactions are discussed.
1. V.N. Kondratyev // Phys. Lett. B 2018. V.782. P.167.
A mean-field and interaction in the particle-hole (p-h) channel are the input quantities for any RPA-based approach to describing Gamow-Teller Resonance and its overtone – Isovector Giant Spin-Monopole Resonance in the $\beta^{(−)}$ -channel (GTR and IVGSMR$^{(−)})$ , respectively). The recent example of such an approach is given in Ref. [1], where main properties of mentioned resonances in $^{208}$Bi are described within the continuum-RPA-based semimicroscopic p-h dispersive optical model. A realistic partially self-consistent phenomenological mean field and Landau-Migdal p-h interaction have been used in this study. Provided that dimensionless strength $g'$ of the spin-isospin part of the mentioned interaction is adjusted to reproduce in calculations of the GT strength function the observable GTR energy, the calculated IVGSMR$^{(−)})$ energy is found to be less (on about 3 MeV) than respective experimental value. In the present study, we attempt to resolve this puzzle by taking into account tensor forces, which lead to mixing $1^+$ spin-monopole and spin-quadrupole excitations. In applying to describing GT strength distribution, tensor forces have been considered in Ref. [2]. Mentioned mixing takes place due to both the spin-orbit term in a mean field (so-called nonsymmetric or non-diagonal approximation in RPA-based approaches employing central forces [3]) and non-central (tensor) forces. Using the mentioned
continuum-RPA-based analysis of Ref. [1] as a starting point, we resolved the above-described puzzle related to evaluation of the IVGSMR$^{(−)})$ energy by taking tensor forces into account. As expected, the strength parameter of the spin-isospin part of non-central forces $g_T'$ is found to be less than the Landau-Migdal parameter $g'$.
This work was partially supported by the Russian Foundation of Basic Research (grant No. 19-02-00660).
Structuring the volumes of nuclei and the complex topology of their surfaces, along with attractive nuclear forces, in certain conditions, electromagnetic forces manifest themselves more significantly. At the line of the stability path of exotic nuclides, these forces begin to prevail.
In this paper, we describe the mechanism of interaction of nucleons in the nucleus volume as the interaction of dipole-dipole intranuclear clusters. Such an interaction and its sign, first of all, will depend on the spatial orientation of nucleons or clusters in the nucleus and, therefore, the interaction potential of electromagnetic forces should include not only the Coulomb repulsion of charged nucleons (clusters) but also the magnetic component, which includes the spin-orbit the interaction of nuclear clusters V = V_{c} + V_{m}(sl), where Vc is the Coulomb potential; Vm (sl) is the potential of the dipole-dipole interaction. The magnetic component of the electromagnetic potential depends both on the total spin of the nuclear clusters and on their spatial position (orbital). This paper considers nucleons and nuclear clusters that form in dipoles. Based on experimental data on the elastic scattering of alpha particles by ^{24}Mg from the found cluster widths for mass numbers from 1 to 4 [2], it was possible to construct the corresponding dipole – dipole interaction in s, p, and d states. In the field of heavy nuclei, neutron-deficient and neutron-rich isotopes, the density of nuclear matter fluctuates with respect to the constant 0.15 fm^{-3} [1]. This fluctuation is associated not only with the deformation of nuclei, but also with the spatial distribution of nucleons within the volume of the nucleus. With an increase in the mass number, the Coulomb repulsive forces cause protons and isolated nuclear clusters to move to the periphery of the nucleus, thereby abnormally increasing the average radius of the nucleus and its deformation, which should affect the density of nuclear matter. From the constructed isotonic dependences of the binding energy of nucleons in the nucleus on the proton excess and deficit, it can be seen that the binding energy per one nucleon decreases quadratically with a decrease and addition of each subsequent proton, which leads to inflation of the nucleus volume and, possibly, the formation of “bubble” nuclei that were still unsuccessfully tried to find in the experiment. Such an idea about inflating the volumes of nuclei was expressed to the authors by Oganessian Yu.T., who drew attention to a particularly significant effect in the field of “Island of stability”.
The isotopic spin in light and medium nuclei is a quantum number that serves to identify the ground and excited states and it is conserved in various nuclear processes. To verify this statement, we considered nucleon decays in the odd nuclei of the 1$p$-shell with isospin $T = 3/2$. By the magnitude of the widths $\Gamma$ of the decaying states, they can be classified into 2 groups. In $^7$Li, $^{11}$B, $^{15}$N nuclei, as a result of the decay of levels with $T = 3/2$, the direct transitions to daughter nuclei levels with $T = 1$ are possible. These are “allowed” transitions. In $^9$Be and $^{13}$C ($^{13}$N) nuclei, direct nucleon decay into levels with $T = 1$ of the formed even-even $^8$Be and $^{12}$C nuclei is not possible by energy. Decays to levels with $T = 0$ are possible only due to Coulomb mixing of the levels $T = 3/2$ and $T = 1/2$. These are “forbidden” transitions. Within the multi-particle shell model, we calculated the nucleon widths $\Gamma$ for $^7$Li, $^{11}$B, and $^{13}$C nuclei, as well as for nuclei mirror to them. The Coulomb mixing of the $T = 3/2$ and $1/2$ levels in $^9$Be and $^{13}$C ($^{13}$N) nuclei was calculated using perturbation theory. A similar situation arises for the $^{12}$C nucleus level with $(J^\pi, T)$ = (1$^+$, 1) at 15.11 $MeV$. Alpha decay of this level into $^8$Be nucleus levels is possible only due to Coulomb mixing of the $T = 1$ and $T = 0$ levels in initial nucleus.
The calculation results show that the $\Gamma$-widths for all “forbidden” transitions are several orders of magnitude smaller than the widths of “allowed” transitions, which indicates a high isospin level of light nuclei.
Correct accounting for residual NN-interaction between valence particles is of utmost importance for structure interpretation of deformed odd-odd nuclei. This interaction manifests itself in such effects as the Gallagher-Moszkowski (GM) splitting of two-quasiparticle doublets, the Newby shift of odd-even spin value levels in K=0 rotational bands, as well as the $\Delta$K=0 mixing of rotational bands due to non-diagonal matrix elements when wave function components of both valence particles exchange.
In two-particle plus rotor model calculations, one usually uses NN-interaction potential parameters obtained via a fit to empirical matrix element values derived from a wide range of well-deformed odd-odd nuclei (see, e.g., [1]). However, it is hard to perform similar studies for transitional nuclei due to a lack of confident experimental data about complete doublets.
Detailed experimental structure studies performed recently for $^{186,188}$Re and $^{192}$Ir [2-4] allowed to obtain empirical values for a number of residual NN-matrix elements responsible for GM-splittings and Newby shifts in transitional deformation region at A$\sim$190. Especially unique are data obtained for $^{192}$Ir where one has three confidently established K=0$^-$ rotational bands.
The residual proton-neutron interaction matrix elements have been evaluated using expressions of [1]. The finite-range $V_{np}$ potential with Gauss radial dependence included both the short, and the long range central forces with spin polarization, as well as the tensor interaction terms. The set of fitted empirical matrix elements included Newby shift values for nine K=0 rotational bands of $^{186,188}$Re, and $^{190,192,194}$Ir. For comparison of NN-interaction potential parameters, values of GM-splittings have been evaluated as well.
It has been found that the long-range NN-interaction can be compensated by variation of the short-range space-exchange Heizenberg interaction strength $V_H$. The latter parameter is most essential in order to reproduce both GM-splittings and Newby shifts. However, while GM-splittings show strong dependence also from spin-exchange Bartlett interaction strength $V_B$ and core polarization, the Newby shifts practically do not depend on values of these parameters, but display dependence on tensor interaction, though weaker than that from $V_H$.
We study the form of the structure functions connected to the zero sound excitations in the symmetric and asymmetric nuclear matter (ANM). The density response $\Pi(\omega,k)$ (the retarded polarization operator) of ANM to the small external field $V_0(\omega,k)= \tau_{z}e^{i\vec q\vec r -i(\omega+i\eta)t}$ is considered. The structure function $S(\omega,k)$ is defined as $S(\omega,k) = -\frac1\pi{\rm Im}\, \Pi(\omega,k)$ [1].
In [2] the three complex branches of the zero sound excitations in ANM were obtained: $\omega_{si}(k)$, $i=n,p,np$. We calculate these branches as solutions of the dispersion equation $E(\omega,k)=0$. Calculations were made in the framework of RPA with the Landau-Migdal quasiparticle-quasihole isovector interaction $F'(\vec\tau,\vec\tau')$ with $F'=1.0$.
It was shown that in the external field $V_0(\omega,k)$ the total polarization operator is the sum [3]: $\Pi= \Pi^{pp} + \Pi^{nn} - \Pi^{pn} - \Pi^{np}$. Expressions for $\Pi^{\tau,\tau'}$ are obtained from the system of equations $M$ of the type similar to the system for the effective fields in [4]: $\Pi^{pp}= \Pi_0^p(1-\Pi_0^n\,F^{nn})/\det M(\omega,k)\equiv D^{pp}/\det M(\omega,k)$, $\Pi^{np} = \Pi_0^p\,\Pi_0^n\,F^{np}/ \det M(\omega,k) \equiv D^{np}/\det M(\omega,k)$. Changing $p\leftrightarrow n$ we obtain $ \Pi^{nn}$, $\Pi^{pn}$. Dispersion equation for the frequencies of zero sound excitations is $E(\omega,k)\equiv \det M(\omega,k)=0$. So, the branches $\omega_{si}(k)$ are the zeros of $\det M$ and the poles of $\Pi^{\tau,\tau'}$ by construction.
In our approach $S(\omega,k)$ must be considered as a sum over three independent processes: the widths of the different $\omega_{si}(k)$ correspond to the different decays of excitations. The imaginary part of $\omega_{sn}(k)$ describes in nuclei the semidirect decay due to emission of a neutron, reaction $(\gamma,n)$. Decay of $\omega_{sp}(k)$ accompanied by emission of proton. About of $\omega_{snp}(k)$ we can say that one nucleon is emitted and its isospin is not fixed [2]. We rewrite $S(\omega,k) = \Sigma_i S_i(\omega,k)$.
Near the pole at $\omega\approx {\rm Re}(\omega_{si})$ we approximate $(\det M(\omega,k))^{-1}$ $= {R^i(\omega_{si},k)}/{(\omega-\omega_{si})}$ $+ Reg(\omega,k)$. Here $Reg(\omega,k)$ is a smooth function near the pole. This permits us to write
$S(\omega,k)_i= \,-\frac1{\pi} {\rm Im} [\Sigma_{\tau,\tau'}(D^{\tau\tau'}(\omega,k))\,R^i(\omega_{si},k)/(\omega-\omega_{si}) + Reg]$. Then, let define the envelope curve of the pole terms $S^e(\omega,k)= -\frac1\pi \Sigma_{\tau,\tau'} {\rm Im} [D^{\tau,\tau'}(\omega,k) \Sigma_i\,R^i(\omega_{si},k)/ (\omega-\omega_{si})]$.
We demonstrate results for ANM with asymmetry parameter $\beta=0.2$ Fig.1. In the left figure the branches $\omega_{sn}(k)$, $i=n,p,np$ are shown [2]. In the right figure $S^e(\omega,k)$ are presented for $k/p_0=0.6$ and $k/p_0=0.2$ ($p_0=0.268$GeV). For $k/p_0=0.6$ the structure functions for the different processes $S_i(\omega,k)$, $i=n,p,np$ are presented (the numbers $1,2,3$, correspondingly). As it was expected the form of the structure function is decomposed over the contributions of the definite processes, corresponding to $\omega_{si}(k)$. The widths of maxima ($right$) are determined by the imaginary parts of $\omega_{si}$ ($left$).
[1] E.Lipparini, "Modern Many-particle Physics", 2003, World Scientific Publishing Co.
[2] V.A.Sadovnikova, M.A.Sokolov, Bull.Russ.Acad.Sci.Phys., v.80,p.981(2016); eprint 1807.09580.
[3] A.Pastore, D.Davesne, J.Navarro, Phys.Rept.v.563,p.1(2015).
[4] A.B.Migdal, D.F.Zaretsky, A.A.Lushnikov, Nucl.Phys.,v.A66,p.193(1965)
Приведены первые результаты новых экспериментов по исследованию полных ядерных сечений фотопоглощения в области пигми резонанса (от 5 до 10 МэВ), выполненных на ЛУЭ-8-5 ИЯИ РАН. Начало экспериментов стало возможным после выполнения методических работ по модернизации ускорителя и системы формирования гамма пучка. Описан метод полного фотопоглощения, который ранее использовался в области гигантского дипольного резонанса (10–30 МэВ) и теперь адаптируется к области низких энергий. Этот метод позволяет получить данные о статической и динамической деформации и квадрупольных моментах исследуемых ядер.
Numerical solution of the time-dependent Schrodinger equation (TDSE) 1 is used for studying neutron transfer processes at near-barrier energies. The evolution of the wave functions for outer neutron is determined for reactions $^{181}$Ta($^{18}$O,$^{19}$O). TDSE allows us to visualize the dynamics of taking place processes [1-3]. The transfer probabilities are calculated for outer neutron shells of the colliding nuclei. The results of calculations of transfer cross sections are in satisfactory agreement with experimental data [4] for reaction $^{181}$Ta($^{18}$O,$^{19}$O). High probability of neutron transfer from the $^{181}$Ta nucleus to the 2$s$ orbital of $^{18}$O nucleus at near-barrier energies has been yielded (see Figure 1). In previous our work [4], differential cross sections for the formation of oxygen isotopes in the reaction $^{18}$O + $^{181}$Ta have been measured at projectile nucleus energy 10$A$ MeV on the high-resolution magnetic spectrometer MAVR. Theoretical analysis has been performed in the DWBA formalism using the FRESCO code under the assumption of sequential neutron transfer mechanism.
1 A.K.Azhibekov, V.V.Samarin, K.A.Kuterbekov, Time-dependent calculations for neutron transfer and nuclear breakup processes in $^{11}$Li+$^{9}$Be and $^{11}$Li+$^{12}$C reactions at low energy, Chinese Journal of Physics 65 (2020) 292.
2 Yu.E. Penionzhkevich, Yu.G. Sobolev, V.V. Samarin et al., Energy dependence of the total cross section for the $^{11}$Li+$^{28}$Si reaction, Phys. Rev. C 99 (2019) 014609.
3 Yu.E. Penionzhkevich, Yu.G. Sobolev, V.V. Samarin, M.A. Naumenko, Peculiarities in total cross sections of reactions with weakly bound nuclei $^{6}$He, $^{9}$Li // Physics of Atomic Nuclei 80 (2017) 928.
4 A.K. Azhibekov, V.A. Zernyshkin, V.A. Maslov, Yu.E. Penionzhkevich et al., Differential Production Cross Sections for Isotopes of Light Nuclei in the $^{18}$O + $^{181}$Ta Reaction // Physics of Atomic Nuclei 83 (2020) 94.
Experimental studies and theoretical calculations of photoneutron reactions on light palladium isotopes $^{102}Pd$ and $^{104}Pd$ were performed. The target from a natural mixture of palladium isotopes was irradiated with brake γ-quanta on the RM-55 electron accelerator at an electron energy of 55 MeV. Absolute yields of photonuclear reactions on $^{102}Pd$ and $^{104}Pd$ isotopes with up to three neutrons are determined. Comparison with the results of calculations using the TALYS [1] and the estimated cross sections from the KAERI library [2] showed that in all cases, the theoretical cross sections of photoneutron reactions are overestimated. This is due to the fact that the theoretical calculations of partial cross sections did not take into account the isospin splitting of GDR, which should lead to a significant increase in the share of photoproton reactions and a decrease in the share of photoneutron reactions in the full cross section of photoabsorption on the $^{102}Pd$ and $^{104}Pd$ isotopes.
[1] A.J.Konig, S.Hilaire, M.C.Duijvestijn, in Proceedings of the International Conference on Nuclear Data for Science and Technology. 2007, Ed by Bersillon O. et al. EDP Sciences (Nice, France, 2008). p. 211
[2] Y.O.Lee, Y.Han, J. Chang, KAERI Photonuclear Data Library, KAERI/TR-1512/2000 (Korea Atomic Energy Research In-stitute, 2000).
Today, one of the fundamental problems in physics of nuclear reactions is a quantitative description of the elements formation in the Universe. These studies lead to an understanding of the mechanisms and processes that occur in stars. When analyzing the nuclear reaction experimental data, playing a key role in astrophysical studies it becomes necessary to use interaction potentials. These potentials allow with good accuracy to take into account the effects of particles transfer and particles (clusters) interaction [1]. The building of these potentials is also associated with an important fundamental problem - the explanation (prediction) of the astrophysical spectroscopic factor behavior for the nuclear fusion reactions near the Gamow window. It was experimentally obtained that during the fusion of carbon and oxygen nuclei in this mass region one can observe the resonance behavior of the reaction cross section. Such resonances have been not yet fully described by the existing nuclear models [2]. In addition, due to the ambiguity of the potential choice, the theoretical predictions for low energies have different values (by several orders of magnitude) in this energy range.
In present work the nuclear reaction 12C + 16O was studied in the framework of a potential model. Several types of potentials obtained in the cluster [3], semi-microscopic [4] and phenomenological approaches [5] were discussed. It was shown that the excitation function may contain “false” resonance states. In addition, the discrete uncertainty of potentials was eliminated by using the analysis of the cross section in the low-energy region.
Acknowledgments
The reported study was supported by RFBR, research project No. 20-02-00295.
References
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In this work, an experimental study of $^{89}Y$ the photodisintegration is performed. Absolute yields and average cross sections weighted by the bremsstrahlung were measured for photoneutron reactions on $^{89}Y$ at the upper limit of 55 MeV brake photons. The measured yields and average cross sections weighted by the bremsstrahlung are compared with the yields of reactions calculated from theoretical cross sections of photoneutron reactions based on the TALYS and with the results of experiments performed on beams of quasimonochromatic [1,2,4] and brake photons [5-8] and the estimated cross sections. The average cross section calculated in this work, weighted by the bremsstrahlung for the photoneutron reaction (γ, 1n) is consistent with the results of the calculation according to the TALYS and the cross sections from [1, 4].
[1] B.L.Berman et al. // Phys.Rev. 1967. 162. P. 1098.
[2] A.Lepretre et al. // Nucl. Phys. A. 1971. 175. P. 609.
[3] V. V. Varlamov, A. I. Davydov, V. N. Orlin, N. N. Peskov. // Bull. Russ. Acad. Sci.: Physics. 2017. 81. P. 664.
[4] L.M.Young // PhD Thesis, Champaign: Illinois University, 1972.
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[6] M.Zaman et al. // J. Radioanal. Nucl. Chem. 2014. 299. P. 1739.
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The flux-weighted average cross-sections <σ(E)> and the isomeric yield ratios IR for the 93Nb(γ,4n)89m,gNb and 93Nb(γ,5n)88m,gNb reactions were studied. The 93Nb targets were irradiated with the bremsstrahlung beam for the end-point bremsstrahlung energies Eγmax = 36-91 MeV using the electron linac LUE-40 RDC “Accelerator” NSC KIPT. The induced γ-activities of the samples were measured using a semiconductor HPGe detector with the 20% absolute efficiency and the 1.8 keV energy resolution at the 1332 keV 60 Со γ-line.
The obtained experimental values of <σ(E)> were compared with the data from [1] and the theoretical values calculated using computer code TALYS1.9 (presented in figures). For the case of the 93Nb(γ,4n)89tNb reaction the theoretical results from TALYS 1.9 and found <σ(E)> are in good agreement. The comparison of the ob-tained <σ(E)> values for m- , g-states of the 93Nb(γ,5n)88m,gNb reaction and isomeric yield ratios IR with the calculations performed in TALYS 1.9 shows satisfactory agreement.
The photonuclear reactions 93Nb(γ,n)92mNb and 93Nb(γ,3n)90tNb were investigated by the γ-activation method using a bremsstrahlung beam generated from an electron linac LUE-40 RDC “Accelerator” NSC KIPT. The flux of bremsstrahlung γ-quanta was controlled using a monitor target from natural molybdenum and the 100Mo(γ,n)99Mo reaction cross-section values.
The experimental cross-sections <σ(E)>, averaged over the bremsstrahlung spec-trum in the energy interval from the reaction threshold to the end-point bremsstrahlung energies Еγmax = (36-91) MeV, were determined for the reactions 93Nb(γ,n)92mNb and 93Nb(γ,3n)90tNb. The obtained values of <σ(E)> (presented in Figures) are in reasonable agreement with the estimates calculated using computer code TALYS 1.9 and with experimental data from [1].
Nuclear reactions with various bombarding particles serve as an important source of information both on the mechanisms of nuclear reactions and on the properties of the excited states of atomic nuclei.
This work presents work results of investigation of the isomeric yield ratios $Y_{\rm m}/ Y_{\rm g}$ of the $^{86}\rm S(\gamma, n)^{85\rm m,g}\rm Sr$, $^{86}\rm Sr(n, 2n)^{85m,g}\rm Sr$, $^{81}\rm Br(\gamma, n) ^{80m,g}\rm Br $ and $^{81}\rm Br(n, 2n) ^{80\rm m,g}\rm $Br reactions. The isomeric yield ratios were measured by the induced radioactivity method. Samples of natural Sr and Br have been irradiated in the bremsstrahlung beam of the betatron SB-50 in the energy range of $10 \div 35 \rm MeV$ with energy step of 1 MeV. For 14 MeV neutron irradiation, we used the NG-150 neutron generator.
The gamma spectra reactions products were measured with a spectroscopic system consisting of HPGe detector CANBERRA with energy resolution of $1.8$ keV at 1332 keV gamma ray of $^{60} \rm Co $, amplifier 2022 and multichannel analyzer 8192 connected to computer for data processing. The filling of the isomeric and ground levels was identified according to their γ lines. Values $Y_{\rm m}/ Y_{\rm g}$ at $E_{\gamma,\rm max}=30 \rm MeV$ for the reaction $(\gamma, n)$ on nuclei $^{81} \rm Br $ and $^{86} \rm Sr $ are respectively: $0.46 \pm 0.02$ and $0,56 \pm 0.04$. In the range $26 \div 35$ MeV the isomeric yield ratios $Y_m/ Y_g$ of the reaction $(\gamma, n)$ on $^{81} \rm Br $ and $^{86} \rm Sr $, are obtained at first. Using the isomer yield ratio and the total cross section of the $(\gamma, n)$ reaction on $^{81} \rm Br $ and $^{86} \rm Sr $ [1] received the cross sections of $(\gamma, n) ^m$ and $(\gamma, n) ^g$ reactions. The cross section isomeric ratios at $E_{\gamma}=E_{\rm m}$ are estimated.
The experimental results have been discussed, compared with those of other authors as well as considered by the statistical model [2]. Theoretical values of the isomeric yield ratios have been calculated by using code TALYS-1.6.
Nickel is a part of most stainless steels, therefore, the cross section for the helium production on the nuclei of the nickel isotopes is significant for evaluation of radiation damages in structural materials of reactors. 58Ni is the main isotope in the natural mixture (58Ni 68.27%, 60Ni 26.10%, 61Ni 1.13%, 62Ni 3.59%, 64Ni 0.91%); therefore, its contribution is one of the determining ones.
The cross-section of the 58Ni (n, α) 55Fe reaction was obtained on a solid target using new low-background digital spectrometer, based on an ionisation chamber with Frisch grid. The neutron flux was monitored using the 238U fission reaction. Monoenergetic neutrons for the experiment were obtained at the accelerator complex of JSC "SSC RF-IPPE”" in the reaction D(d,n)3He. The neutron spectrum was monitored during the experiment. The measurements were carried out for neutrons with energies from 3.5 to 7.5 MeV. The obtained data are in satisfactory agreement with the data of other authors and the available theoretical estimation, presented in the main libraries of evaluated data.
Investigation of energy dependence of light charged particles emission from (p,x) reaction with 120Sn nucleus
D. Alimov1, Zh. Mukan1,2, M. Nassurlla1, A. Pan1, B.M. Sadykov1, T.K. Zholdybayev1,2
1 Institute of Nuclear Physics, Kazakhstan;
2 Gumilev Eurasian National University, Kazakhstan;
2 al Farabi Kazakh National University, Kazakhstan;
zhuldiz_mukan@mail.ru
The double-differential and integral cross sections of the reactions initiated by nucleons play a key role in development of the theory of nuclear reactions, verification of computer codes based on them. From another hand such data are necessary for the design of safety systems for power reactors, development of advanced nuclear technologies, in particular, hybrid nuclear energy systems (ADS-Accelerator Driven System) [1,2]. The experiment with protons accelerated to energy of 30 MeV was performed on an isochronous cyclotron U-150M of the Institute of Nuclear Physics. The double-differential cross sections of the reactions with light particles in exit channels were measured in the angular range 30-135o with angle increments of 15°. Theoretical analysis of the obtained experimental results was performed within the framework of the TALYS and PRECO calculation code, which is widely used in interpreting many experimental results. To describe the complete inclusive spectra of scattered particles, all possible mechanisms of nuclear reactions were taken into account. A satisfactory agreement between experimental and calculated values has been achieved. A distinction between direct nuclear reactions, pre-equilibrium decay and equilibrium emission at different incident protons energy for 120Sn(p,x) reaction was established.
[1] Y. Ikeda et al., Journal of Nuclear Science and Technology,suppl.2, (2002) 13.
[2] A. Ignatyuk et al., Atomic Energy 116 (2014) 209.
The flux-weighted average cross-sections <σ(E)> of the photonuclear reaction 100Mo(γ,n)99Mo were determined for the end-point bremsstrahlung energies Еγmax = 30-100 MeV using the γ-activation method. Targets from natural molybdenum were irradiated by the bremsstrahlung beam with a step dEe = 4 MeV using the linear electron accelerator LUE-40 RDC “Accelerator” NSC KIPT. To determine the values of <σ(E)>, we used γ-lines with energies Eγ = 739.5 and 140.5 keV. The cross-section values obtained for these γ-lines coincide within the experimental er-rors. The found values <σ(E)> gradually decrease from 36 mb to 28 mb with in-creasing energy from 36 to 91 MeV.
The theoretical values <σ(E)> were obtained as a convolution of the cross-section σ(E) reaction, calculated using computer code TALYS1.9, and the bremsstrahlung spectra of electrons from GEANT4, calculated using of real energy profiles of electron beam. The comparison of theoretical average cross sections with experimental ones showed a difference of 8-18%, which is mainly determined by the deviation of the real flux of bremsstrahlung quanta from the calculated one. The obtained cross-sections <σ(E)> for the 100Mo(γ,n)99Mo reaction at Еγmax = 30-100 MeV were used as the monitor for measuring of the cross sections for the photo-nuclear reactions on other nuclei.
Strongly intensive observables can be used to measure forward-backward (FB) correlations between charged particles in two separate pseudorapidity intervals. We will present calculations of observables in pp collisions simulated in PYTHIA at the LHC energies, and examine the azimuthal dependence of such correlations.
Within the model of independent statistically identical particle sources, these observables do not depend on the mean value and fluctuations in the number of the sources, and therefore may provide a signature of collective behavior in the system. The magnitude of the FB correlation strength is obtained for different gaps between pseudorapidity intervals and for different combinations of azimuthal windows, selected within the pseudorapidity intervals. The collision energy and multiplicity class dependence of the FB correlations is studied.
This work is supported by the Russian Science Foundation, GRANT 17-72-20045.
We study the phenomenon of high energy proton stopping in the nuclear matter and suggest the effective model that describes this effect. To compare our model with the data of relatively low energy experiment [1] we use the correlation between mean multiplicity and number of so-called grey nucleons - particles, which are knocked out of the nucleus by the incoming proton.
Proton decelerates in the nuclear matter transferring its energy to the production of new particles in inelastic interactions. We introduce the stopping force from hydrodynamics to explain this deceleration in an effective way. The idea is to treat target nuclei as a liquid drop with given internal energy density and volume. As soon as the projectile-proton gets into the target-nuclei the stopping force begins to act on it. With this force we obtain a differential equation that describes relativistic motion of a proton in a nucleus. Setting the final speed - the speed after which binary collisions do not contribute to multiplicity - we calculate the length of the proton's path in the nucleus. This path length cuts out a region, in the nucleus to which we apply the Glauber-like approach to obtain number of binary collisions. (Note that in a pure Glauber approach, the integration extends to the entire space.) The method of calculating dependency of mean multiplicity on impact parameter is also suggested. As an input in this model we use empirical dependency of mean multiplicity on energy in pp-collisions [2] and values of $\sigma^{NN}_{inel}$ [3].
Results on the correlation between mean multiplicity and a number of grey nucleons are compared in this work to the available experimental data on centrality dependence of stopping and $\pi^-$ production in p-Au collisions at a beam momentum of 18 GeV/c [1]. The linear dependence of the correlation between mean multiplicity and grey nucleons predicted by the model is well in line with the experimental data obtained at low numbers of grey nucleons. At the same time, it is shown that the limited acceptance of pion registration can produce a strong deviation from the linearity as observed in the experiment with slow protons at large values of pion multiplicity and number of grey nucleons.
Acknowledgments: the reported study was supported by RFBR, research project No. 18-02-40097
[1] I. Chemakin et al., Phys. Rev. C 60, 024902; https://doi.org/10.1103/PhysRevC.60.024902; arXiv:nucl-ex/9902009
[2] W.Thomé, K.Eggert, K.Gibini [etc.] // Nuclear Physics B129. P. 365-389. doi:10.1016/0550-3213(77)90122-5
[3] P.A. Zyla et al. (Particle Data Group), to be published in Prog. Theor. Exp. Phys. 2020, 083C01 (2020), https://pdg.lbl.gov/2020/hadronic-xsections/hadron.html
The ALICE experiment at the LHC is undergoing a major upgrade during Long Shutdown 2 (2019-2020). In particular, the Time Projection Chamber (TPC) is being equipped with new GEM-based readout chambers and the readout electronics of several detectors is being replaced with faster and more flexible technology. This will allow ALICE to read out most of the detectors in the continuous mode and record minimum bias Pb-Pb events at rates of about 50 kHz in Run 3 (2021-2024) and Run 4 (2027-2030). The ALICE collaboration is also considering the possibility to collect a large sample of proton-proton collisions at interaction rates of about 1 MHz using online and offline preselection of rare events. These goals require a completely new online computing system that will be used to perform fast reconstruction and compression of the data stream. The event selection strategy becomes especially challenging for the case of rare central diffractive events and ultra-peripheral Pb-Pb collisions characterized by rapidity gaps at forward and backward directions with only few tracks at central rapidity. In this contribution, the motivation for studying central diffractive and ultra-peripheral events is presented, and feasibility studies for their selection in runs 3 and 4 will be given.
The measurements of exclusive $\pi^+n$ and $\pi^0p$ electroproduction with the CLAS detector in Hall B at Jlab provided the dominant part of the world data on observables of these channels [1] stored in the CLAS Physics Data Base [2]. The data on exclusive $N\pi$ and $\pi^+\pi^-p$ electroproduction are the major source of the information on nucleon resonance ($N^*$) electroexcitation amplitudes. They offer insight into the $N^*$ structure and strong QCD dynamics which underlie the nucleon resonance generation from quarks and gluons [1,3,4]. The approach for evaluation of the four-fold $N\pi$ differential cross sections and unpolarized, transverse-transverse, longitudinal-transverse exclusive structure functions will be presented in the talk. The estimates of $N\pi$ electroproduction observables have become available from the measured with the CLAS detector differential cross sections for the first time. They cover a broad kinematics area of the invariant masses of the final hadron system of $W$ $<$ 1.7 GeV and the photon virtuality range $Q^2$ $<$ 5.0 GeV$^2$. The estimated $N\pi$ cross sections and exclusive structure functions are of particular importance both in the studies of the $N^*$ structure in 1-dimension and in exploration of the ground nucleon structure in 3-dimesions from the results on the chiral-odd generalized parton distributions constrained by the data of deeply virtual $N\pi$ electroproduction.
[1] I.G. Aznauryan and V.D. Burkert, Electroexcitation of Nucleon Resonances, Prog. Part. Nucl. Phys. 67, 1 (2012).
[2] CLAS Physics Database, http://clasweb.jlab.org/physicsdb
[3] V.D. Burkert et al., The Nucleon Resonance Structure from the $\pi^+\pi^-p$ Electroproduction Reaction off Protons, Moscow Univ. Phys. Bull. 74, 243 (2019).
[4] V.D. Burkert and C.D. Roberts, Roper Resonance: Toward a Solution to the Fifty Year Puzzle, Rev. Mod. Phys. 91, 011003 (2019).
The full ATLAS Run 2 data set with time-integrated luminosity of 139 fb$^{-1}$ in
the diboson channels in hadronic final states is used to probe a simple model
with an extended gauge sector (EGM), proposed by Altarelli et al., and often taken
as a convenient benchmark by experimentalists. This model predicts new
charged $W'$ and neutral $Z'$ vector bosons with modified
trilinear Standard Model gauge couplings, decaying into
electroweak gauge boson pairs $WZ$ or $WW$, where $W$/$Z$ decay hadronically.
Exclusion limits at the 95\% C.L. on the
$Z'$ and $W'$ resonance production cross section times branching
ratio to electroweak gauge boson pairs in
the mass range of $\sim$ 1 -- 5 TeV are here converted to
constraints on $W$-$W'$ and $Z$-$Z'$ mixing parameters and
masses for the EGM.
We present exclusion regions on the
parameter space of the the $W'$ and $Z'$ by using the full Run 2
data set comprised of $pp$ collisions at $\sqrt{s}=13$ TeV and
recorded by the ATLAS detector at the CERN LHC. The obtained
exclusion regions are significantly extended compared to
those obtained from the previous analysis performed with Tevatron
data as well as with LHC data collected at 7 and 8 TeV in Run~1
and are the most stringent bounds to date.
The Multi-Purpose Detector, to be operating at NICA, aims to study the phase diagram of strongly interacting matter at high baryonic densities. One of the sensitive tools to probe the critical behaviour is the analysis of event-by-event fluctuations. Strongly intensive observables are considered to be especially sensitive to the phase transitions as they suppress trivial volume fluctuations. In this contribution, we present the performance of the MPD detector in measurements of fluctuations via strongly intensive quantities between multiplicities and transverse momenta in different kinematic acceptances. The results from the full MPD simulation and reconstruction chains are demonstrated. The dependence of the considered fluctuation observables on the centrality estimation method is discussed as well.
This study was funded by RFBR according to the research project No 18-02-40097.
Results on the Event-by-event pseudorapidity fluctuations of the relativistic charged particles produced in O-AgBr interactions at 60 and 200A GeV/c will be presented. To compare the experimental results, analysis of AMPT simulated data will also be presented. Results are suggestive of the presence of pseudorapidity fluctuation and strong correlation.
In the present articles an attempt has been made for the determination of multiplicity distributions of the secondary charged particles produced in the central region of relativistic heavy ion collisions. Due to sophisticated measurement of energy in the nuclear emulsion experiment only some particles having special criteria could be selected to measure their energy with consenting accuracy. A hypothetical model is proposed to correlate the energy of the produced particles to their emission angles so that it becomes easy to estimate the energy distribution in terms of measured emission angle. The proposed model is constructed upon statistical thermodynamic assumptions. Moreover, two additional base functions are originated that play the role of the statistical angular weight factor and the nuclear density of the compressed nuclear matter at the moment of particle emission. The prediction of the model are compared with complete set of measured data of the reactions of proton, helium, carbon and neon nuclei with the composite emulsion nuclei as target at an energy of 14.6A GeV.
The Time-Projection Chamber (TPC) is the main tracking detector and charged particles identification of the MPD central barrel. The TPC-MPD will provide:
- The overall acceptance of |η|<1.2;
- The momentum resolution for charge particles under 3% in the transverse momentum range 0.1<pt<1GeV/c;
- Two-track resolution of about 1 cm;
- Hadron and lepton identification by dE/dx measurements with a resolution higher than 8%.
These requirements must be satisfied at the NICA design luminosity, charged particle multiplicity ~ 1000 in central collisions and the event rate about 7 kHz.
The TPC design and structure are similar to those of the TPCs used in the STAR, ALICE and NA49 experiments.
The TPC being a large but conceptually simple detector must be constructed with very high precision to reduce nonlinear systematic effects. High stability of the mechanical structure and uniformity of the drift field, the temperature, the drift gas purity and the gas gain have to be provided to get precise track reconstruction and energy-loss measurements.
The structure of the TPC, the basic design parameters of the TPC and the basic TPC configuration are presented. Developed design tools for the TPC assembling, laser calibration system and parts of the TPC cooling system are provided.
The Monte-Carlo simulation of the trigger detector performance and interaction trigger efficiency for Au + Au collisions in BM@N[1-2] experiment at energy of 4 A GeV was performed with a code DCM-QGSM[3] + GEANT4[4]. The Au ion fragmentation and detection of spectator neutrons by a neutron zero-degree calorimeter and charged nuclear fragments by a forward Cherenkov counter were studied with the aim to include this information to the fast interaction trigger providing more reliable selection of events by centrality.
[1] M Kapishin 2016 The fixed target experiment for studies of baryonic matter at the nuclotron (BM@N), Eur. Phys. J. A 52 (2016) 213.
[2] V I Yurevich, O I Batenkov, G N Agakichiev, V A Babkin, S N Basilev, D N Bogoslovsky, L G Efimov, S P Lobastov, I A Philippov and A A Povtoreyko, Beam tests of Cherenkov detector modules with picosecond time resolution for start and L0 trigger detectors of MPD and BM@N experiments 2015 Phys. Part. Nucl. Lett. 12 (2015) 778.
[3] V D Toneev , K K Gudima, Particle Emission In Light And Heavy Ion Reactions // Nucl. Phys. A. 1983. V. 400, P. 173-190.
[4]J Apostolakis, M Asai, A G Bogdanov, H Burkhardt, G Cosmo, S Elles, G Folger, V M Grichine, P Gumplinger, A Heikkinen et al., 2009 Geometry and physics of the Geant4 toolkit for high and medium energy applications Radiation Physics and Chemistry, 78 859-873
Correlations between multiplicity of charge particles and mean transverse momentum was observed experimentally in pp collisions from top SPS energy to LHC energy. The change of the correlation function’s shape with collision energy was successfully described by the multi-pomeron exchange model [1,2] as an interplay of string fusion and energy-momentum conservation. The situation at lower collision energies where role of resonance decays would increase can be studied by the NA61/SHINE experiment at SPS and by the forthcoming MPD experiment at NICA. In prior to the experimental analysis the phenomenon was studied using Monte Carlo event generators.
In this contribution Monte-Carlo simulations results will be presented for the pt-n correlation function and correlation coefficient calculated for different electric charge combinations. The role of limited experimental acceptances of NA61/SHINE and MPD facilities will be discussed. Moreover, he dependency of the correlation coefficient on the width of considered rapidity interval is studied.
This study was funded by RFBR according to the research project No 18-02-40097.
[1] N. Armesto, D. Derkach, G. Feofilov, Phys. Atom. Nucl. 71 (2008) 2087-2095
[2] E. Bodnia et al., AIP Conf. Proc. 1606 (2015) 1, 273-282
The method of induced activity was used to study photonuclear reactions on a natural mixture of erbium isotopes. The experiment was performed on a bremsstrahlung of an RM55 electron accelerator at an electron energy of 55 MeV. The study examined the possibility of producing carrier-free $^{166}Ho$ isotope in photonuclear reactions on a natural mixture of erbium isotopes. Experimental data on the cross-sections of photoproton reactions on Er isotopes are not available in the literature. The yields of the formation of $^{161,165}Er$ isotopes as a result of $^{nat} Er(\gamma, in)$ reactions, the target nuclide $^{166}Ho$ and the side nuclide $^{165}Ho$ as a result of $^{nat}Er(\gamma, in1p)$ reactions were measured. The yield of $^{166}Ho$ formation under the experimental conditions was approximately $4 \cdot 10^4 Bq / (\mu A \cdot h \cdot g/cm^2)$. The experimentally obtained yields of photonuclear reactions are compared with the yields calculated using theoretical cross-sections of photonuclear reactions from the combined model of photonuclear reactions (CMFR) and the TALYS program. There is a good agreement between the experimental data and the results of the calculation by CMFR for both photoneutron and photoproton reactions.
Both radiation therapy and chemotherapy are efficient methods of cancer treatment [1]. Efficiency of the hadron therapy is based on the phenomenon of the Bragg peak. Parameters of the Bragg peak such as its distance from the entrance pointe and maximum magnitude depend on kind of particles in the therapeutic beam and it energy, physical properties of target medium and its chemical composition [2]. During chemotherapy and some time after it chemical composition of tissues may be changed so it may leads to changes of the Bragg peak parameters in the case of combined treatment. Influence of the chemotherapy on the dose-depth distribution is studied. The computational models are proposed and different schemes of chemotherapy have been considered for the proton and carbon ion beams. The study is based on the numerical simulations with the software package Geant4.
References
Patient exposure from Computed Tomography (CT) was simulated using Monte Carlo method. The model of rotating source was implemented previously.
Conversion coefficients from measured dose indexes to doses in organs and tissues of patient were determined. Each coefficient is a quotient of calculated organ dose divided by a weighted calculated computed tomography dose index ($CTDI_w$). Simulation using Monte Carlo method requires the energy spectrum of incident radiation. The anode angle and total beam filtration determine the energy spectrum. When these quantities are unknown, measurements of attenuation in cylinder dosimetric phantom can be used to characterize the spectrum.
A comparison of radiation doses to patients during CT examinations was performed in [1] and showed that the $CTDI_w$ measured in CT scanners from various manufacturers have large discrepancies while input settings are the same. Organ doses differed by a factor of two and the similar image quality. Hence, the scanner-specific doses should be calculated. However, when a conversion coefficients are studied, their variation is much smaller (several percent). This suggests using of a limited set of conversion coefficients, calculated for a number of combinations of filters and anode angles. These values can be matched to calculated coefficients based on $CTDI_W$ measurements.
Energy spectrum can be characterized using the quotient of $CTDI_w$ measured in cylinder dosimetric phantom to $CTDI_{air}$ measured free-in-air. This relation lies in the range of 0.27 to 0.77 for different CT scanners [2]. Based on this relation appropriate set of conversion coefficients can be chosen to estimate organ doses. Current quality assurance protocols requires only phantom measurements of $CTDI_w$. This approach can provide doses to adults only [3].
Apart from the energy spectrum beam profile also impacts the dose. Simulation needs the shape of bow-tie filter that determines the beam profile. The beam profile can be measured using ionization chamber while the X-ray tube position is fixed. Several beam profiles were published [4] and can be used in simulation of specific scanners.
Laser - plasma generation of ultra-short intense neutron pulse
$^1$Andreev А.А., $^2$Komarov V.А, $^3$Platonov К.Yu.
$^1$Saint-Petersburg State University, 199034 UniversitetskayaEmb. 7-9, St. Petersburg, Russia
$^2$FGUP scientific research institute of Complex Tests of Optiko-electronic Devices 188540, Leningrad region, Sosnovy Bor
$^3$Peter the Great St. Petersburg Polytechnic University,
195251 Polytechnicheskaya st. 29, St. Petersburg, Russia
Acceleration of Deytron nuclear in thin (micron size) laser targets (polyethylene C$_2$D$_4$) to a МэВ energy and the subsequent interaction with the secondary targets from D$_2$O, LiF, Be of 1 mm thickness was considered. It is shown, that at the energy of laser pulse of 250 J, duration 10 ps, diameter of the laser spot 5 microns and intensity 1.3x10$^{20}$ W/cm$^2$ in a secondary target there is the generation of ultrashort (<30 ps) neutron pulse containing from 4x10$^9$ (for LiF secondary target) to 10$^{10}$ neutrons (Be target) with characteristic energy about 10 MeV. Pulse intensity of a neutron flux from a surface of a secondary target reaches 10$^{20}$ neutrons/cm$^2$s, that exceeds the intensity of neutron flux of the reactors making in a continuous regime ~10$^{15}$ neutrons/cm$^2$s. Angular distribution of neutrons has a maximum in laser pulse direction and semi-width about ±60$^o$ from this direction is calculated. At 10 Hz repetition rate of a laser pulse, the realization quasi-stationary neutrons source with average intensity about 10$^{12}$ neutrons/cm$^2$s is possible. In laser-plasma neutron source a laser pulse with less (~ 100 fs) duration and upper (up 1 kHz) repetition frequency may be used. Peak intensity of a neutron flux thus will decrease on 2 order, however average intensity will remain constant. Despite of smaller average intensity and essentially smaller total number of neutrons, some potential application of laser-plasma super-short neutron pulses can be interesting for neutron spectroscopy of ultrafast (tens ps) physical, chemical and biological processes, which cannot be realized by means of traditional neutron sources.
Monitoring the accumulated dose in the population from natural terrestrial radionuclides and timely assessment of the maximum dose to prevent potential risks of radiogenic oncological diseases is an important and one of the priority tasks. The main source of the accumulated dose by the population is the natural terrestrial radionuclides that enter the body through human life, and this problem is international in nature [1].
The concentration of chemical elements in the organs and tissues of the human body pretty much depends not only on the use of certain products, but also on geographical residence with a different geological landscape [2]. Different concentrations of chemical elements accumulated in various organs or tissues entail the accumulation and corresponding distribution of natural radionuclides. In this work, the authors developed a software-mathematical complex [3], which allows you to simulate the distribution of natural nuclides and radionuclides in the organs and tissues of the human body. Unlike existing software systems that simulate the interaction of radiation with biological objects, such as Geant4-DNA, etc. [4], the developed program simulates the spread of radionuclides throughout the body, taking into account the conversion factors from one organ to another. Thus, a mathematical calculation based on experimental accumulation coefficients and methods for calculating the doses of ICRP makes it possible to calculate the internal radiation doses of the corresponding organs and tissues. Such modeling allows us to calculate the risks of cancer due to internal exposure to incoming natural terrestrial radionuclides. The distribution of the studied radionuclides is visualized, which allows you to visually study the potential areas of internal sources of radioactive radiation.
The result of the development of this software was the collective work of a team of authors, which was carried out in an open-type nano-technological laboratory at KazNU al-Farabi from 2018 to 2020. with the support of state grant funding for basic research (project: "Fundamental research on the mechanisms of formation of nanoscale oncradiogenic structures in the body and the development of anti-cancer rapid devices for their detection", No. IRN AP05131884).
The problem statement and a mathematical model of the interaction of a cryogenic and then a plasma target with powerful jets (plasma and laser beams) are presented taking into account the external and spontaneous magnetic field. The authors developed a numerical technique and a method for calculating the characteristics of a target and the parameters of compressing beams and jets in a strong magnetic field.
The processes in the target are simulated and the results of the calculation of the plasmodynamic parameters inherent in similar magnetic inertial fusion facilities are presented. The calculation results are presented in the form of graphical dependences of the main parameters of the plasma target (temperature, pressure, density) and magnetic field on the energy characteristics of the powerful radiation and compression system (laser radiation intensity, plasma jet velocity) over the radius of the target at different times.
This work was supported by the Ministry of Science and Higher Education of the Russian Federation.
Photonuclear technologies for the production of 18F, 99Mo, 149Pm, 153Sm and 175Yb with high specific activity were developed at the linear electron accelerator NSC KIPT. The method of recoil nuclei using oxides of nanoparticles of these elements to obtain isotopes of the lanthanide group and 99Mo was applied. Nanoparticles of CaF2 were used for obtaining 18F.
The proposed photonuclear technologies for the production of isotopes are alternative to the technologies widely used in the world at reactors and cyclotrons. The advantages of these technologies there are high specific activity, high isotopic purity (absence of other isotopes in the form of impurities), and no need to immobilize the resulting radioactive waste. Therefore these photonuclear technologies have no alternative.
Samples in the form of nanoparticles were activated by bremsstrahlung radiation on a linear accelerator with an electron energy of 13 MeV. Activated nanoparticles were used as donors in the reaction of recoil nuclei, and nanoparticles of biocompatible aluminosilicate - as an acceptor. The activity of the isotopes was measured by the Ge(Li)-detector. The ratio of recoil nuclei in aluminosilicate nanoparticles for 99Mo, 149Pm, 153Sm and 175Yb and sodium chloride for 18F ranged from 12.3% to 1.7%.
Also, preclinical studies have been conducted on the accumulation of the 99mTc isotope in blood plasma, isolated tumor cells, and also with the help of various carriers, the functional ability of individual organs of animals on a gamma camera has been registered.
The isotope production with use MoO3 nanoparticles with size 15 nm and of bremsstrahlung with Emax=25 MeV on 10 kW electron accelerator will allow producing 22 mCi/g per day of 99Mo with a high specific activity, which is necessary for manufacturing generators 99mTc-99Mo. For the production of 149Pm, 153Sm and 175Yb with E=25 MeV and a current 260 А it is possible to produce 0.5 Ci during the day by using of targets (30 g) of natural isotope composition. The estimation of the 18F production on an electron accelerator with a power of 10 kW and an energy of 25 MeV can be up to 1 Ci for 4 hours.
Ammonium salts are at the basis for the synthesis of a number of substances, which are used in different medical applications. Ammonium media has no adverse effects on the body. It is chemically and biologically sufficiently stable. These salts often used as a buffer for binding the radionuclide to a chelator, which in turn promotes the binding of the radionuclide to the active part (peptide, antibody, etc.) of radiopharmaceuticals. It is very important to obtain radiopharmaceuticals with the highest specific activity. For this reasons, substances with a minimum content of two-, three-, and tetravalent elements are required for nuclear medicine applications.
In addition, ammonium salts are used as a fluxing agent in soldering for electronic devices that work in the area of low-background experiments (for example, neutrino physics). The solder and flux must meet the requirements of radioactive purity.
The chemical properties of impurities are usually similar to the basic substance, otherwise they would have easily separated in its synthesis. Therefore, developing combined methods of purification is very important.
In this work, we report the production process of a high purified ammonium salt. The initial components for the synthesis of salt was undergo an additional purification by sub-distillation. The synthesis of ammonium salt was achieved with transfer of gas phase ammonia to the acid. The final product obtained is a dry salt of ammonium chloride and ammonium acetate in form of white granules.
To achieve high purity of the final product all the processes were performed in a clean room (JINR, Dubna) with the use of chemically resistant equipment made from pre-purified materials.
A γ-ray screening with ultra-low background spectrometer, an instrumental neutron activation analysis and ICP-MS elemental analysis have been performed to estimate the radioactivity level and composition of the final product. Will be presented comparison results for commercial and custom-made ammonium salts.
The isotope of 186Re is widely used (glass-based TheraSphere, Nordion, Canada and resin-based SIR-Spheres, Australia) for transarterial radioembolism in hepatocellular carcinoma (second in the world in total mortality).
The average -radiation energy of 186Re 1.07 MeV is one of the highest among the radionuclides used in palliative therapy.
The powder of rhenium activated by bremsstrahlung at the Linac of the NSC KIPT. The photonuclear reaction 187Re(,n)186Re was used. After activation, the powder was dissolved in HCl and, according to one of the methods, was homogenized with clinoptilolite particles (2040 μm), which were previously treated with hexadecyltrimethylammonium chloride to more efficiently sorption rhenium. The resulting mixture modified thermally. According to the second method, after the activated powder was dissolved in the HCl solution, electrolysis was carried out at pH=1.5, followed by isolation of 186ReО2 at the cathode in the form of clinoptilolite particles [1].
The proposed methods for obtaining the isotope 186Re can significantly reduce the cost of the procedure of radionuclide therapy in comparison with the used commercial agents.
[1.] E. Salakhova, V. Majidzade, F. Novruzova et all. The Electrodeposition of Rhenium in Alkaline and Acidic Elektrolytes // J. Chem. Chem. Eng. – 2012. – v.6 – p.489-494.
There are 4 known types of interaction in nature, but nowadays the existence of a new force mediated by new unknown bosons is widely discussed in the literature [1], [2]. This work deals with the application of a neutron scattering technique for the search for a new short-range interaction and for setting constraints on the coupling constant of such interaction.
The main idea is to perform an experiment of neutron scattering on the powder of silicon (powder diffraction) and to get the information on scattering amplitude dependence on scattering angle. Within this work the calculations showing the possibility of the idea were made. The coupling constant constraints were obtained using the calibration data of powder diffractometer SPODI from the FRM II reactor, Munich, Germany. It is shown that the new constraints are competitive with the existing ones. Performing a new full-time experiment is expected to provide an improvement of the constraints for about 2 orders for the interaction range λ < $10^{-11}$ m.
The reported study was funded by RFBR, project number 19-32-90202.
At Joint Institute for Nuclear Research (JINR, Dubna, Russia), in the framework of the project TANGRA (TAgged Neutrons and Gamma RAys) [1], we continued the experiments for studying the inelastic scattering of fast neutrons on some important for nuclear science and technology isotopes [2]. We are using several different types of gamma-detectors, such as: NaI(Tl), BGO, Stilbene, HPGe, Plastic scintillators and LaBr3 [3-5]. The design of the experimental setup that includes a ring of gamma-detectors and a neutron generator, allows us to measure the angular distribution of gamma quanta with a good accuracy. A single HPGe gamma-detector and an ING-27 neutron generator we are using to determinate the cross-section of the inelastic neutron scattering reactions. The information about the gamma-ray energy and angular distributions, and cross-sections, makes it possible to test different models, describing neutron-nuclear reactions, and to improve the accuracy of the fast neutron elemental analysis.
The aim of this work is to determine the main characteristics of the experimental setups, such as: gamma and neutron efficiencies, energy and time resolutions, at different source-detector geometries and PMT’s high-voltages, for which point-type standar $^{137}Cs$ and $^{60}Co$ gamma-ray sources and 14.1MeV neutrons were used.
References
[1] TANGRA project, http://flnph.jinr.ru/en/facilities/tangra-project
[2] Valkovic V. 14 MeV Neutrons. Physics and Applications. CRC Press. New York. 2015.
[3] Ruskov I.N., Kopatch Yu N., Bystritsky V.M., et al. // Physics procedia. 2015. 64, No. 2. P.
163-170.
[4] Bystritsky V. M., Grozdanov D. N., Zontikov A. O. et al. // Phys. Part. Nuclei Lett., 2016.
13. P. 54.
[5] Grozdanov D.N., Fedorov N.A., Bystritski V.M. et al. // Phys. Atom. Nuclei 81, 588–594 (2018).
The coordinate detector “Cathodic Strip Chamber” (CSC) is designed to refine the parameters of the track obtained by multilayer GEM detectors inside the analyzing magnet. In addition to improving impulse resolution, an updated track is needed to find the corresponding hit in the ToF400 flight system. The first prototype CSC was tested on the BM@N technical wound in the 55th session of the Nuclotron in 2018. Charge distributions are obtained, coordinate resolution and detector efficiency are estimated. The design of CSC detectors used in the BM@N experiment is described and the results of studies of their characteristics are presented.
The colliding beams of heavy ions (Au+Au, Pb+Pb or Bi+Bi), currently planned for NICA at JINR with the average luminosity at the level of $10^{27} $cm$^2$/s, will provide the vast amounts of precise data at the center-of-mass energies up to 11 GeV per pair of nucleons. This will give the possibilities for the detailed, event-by-event studies of properties of high-density baryonic matter in the region of the expected onset of deconfinement, as well as for the search of the critical first-order end-point of the phase diagram of strongly interacting matter and of some signals of chiral symmetry restoration. With the aim of selection the events of interest, it was proposed in [1] to create a fast beam-beam collisions monitor, which would determine the time and space of each ion-ion collision, providing also the event-by-event information on the relevant multiplicity of charged particles. Circular (segmented ring-shaped) detectors on the microchannel plates (MCP) with high timing characteristics (signal duration below $1$ ns) were suggested to be placed in vacuum of the beam-pipe at some distance from the interaction of the ion beams. The multipad readout system has to ensure the time-of-flight measurements with the accuracy below $50$ ps, and multiplicity and azimuthal distributions of particles produced in collision.
In this report, we present our results of MC simulations of the beam-beam collisions monitoring system at NICA based on the MCP detectors. Different generators SMASH $1.8$ [2], UrQMD [3], DQGSM [4] were used with the purpose to estimate the accuracy in determination of the position of the interaction point and multiplicity in the event. The assessments take into account the arrival times of particles to the detector, the rising edge of the current pulse in the MCP channels, the influence of communication lines, electronic equipment, and information retrieval technology.
The performed calculations show that it is the signal formation time in the microchannel plates that brings the main contribution to the error in determination of the interaction point. Calculations confirmed also the possibility of determining by this compact detector system the event multiplicity by using MCP detectors in the counting mode. The possibilities of event-by-event measurements of arrival times for different types of charged particles coming from the interaction point are also discussed.
Acknowledgments: the study was supported by RFBR, research project No. 18-02-40097
Schottky cavity pick-ups have proven to be fast and sensitive detectors
for use in storage ring experiments with radioactive ion beams (RIB)
relevant for nuclear astrophysics [1]. Cavity pick-ups with longitudinal
sensitivity have been successfully used in the storage ring ESR in GSI
facility [2-4], CSRe in Lanzhou [5] and in R3 ring in RIKEN [6]. Some
initial studies were carried out in order to extend the concept to
sensitivity in transverse direction for use in different storage rings
[8-10]. In the current work we report on the progress of the modelling
of a prototype of a position-sensitive resonant Schottky cavity for the
R3 storage ring in the RIKEN facility.
References
[1] Litvinov Yu. A. et al. 2013 Nucl. Instrum. Meth. B 317
[2] Sanjari M. S. et al. 2013 Phys. Scr. T156
[3] Sanjari M. S. et al. 2020 submitted to Rev. Sci. Instrum.
[4] Kienle P. et al. 2013 Phys. Lett. B 726 4–5
[5] Wu J. et al. 2013 Nucl. Instrum. Meth. B 317
[6] Suzaki F. et al. 2015 Phys. Scr. T166
[7] Sanjari M. S. et al. 2015 Phys. Scr. 014060
[8] Chen X. et al. 2016 Nucl. Instrum. Meth. A 826
[9] Chen X. et al. 2015 Hyperfine Interact. 5
[10] Dmytriiev D. et al. 2020 Nucl. Instrum. Meth. B 463
Diamond radiation detectors became more popular in the neutron radiation measurements at these days. It’s happen due to the such detectors advantages as small sensitive volume (which lead to less distortion from detector housing in the detected neutron spectra), high radiation, temperature and chemical resistance, low energy consumption, ability to work in high magnetic fields and low sensitivity to the background gamma- or x-ray radiation. Besides this, there is decreasing in cost of such detectors due to the development of artificial diamond growth.
In this paper, we present the results of the development and creation of two algorithms for neutron spectrum unfolding with a diamond detector responses. One of the algorithms is based on the detector response decomposing procedure into the sum of basic components, which are the product of the responses matrix. To implement the decomposition procedure, a modified nonlinear least squares method is used in which the main modification is a condition for mandatory non-negativity of the problem possible solutions. The second algorithm is a variation of the Tikhonov regularization method for solving the unfolding spectra problem. For the second algorithm there also performed searching the optimal value of the regularization parameter value.
Verification of the created algorithms was carried out using model spectra and detector responses obtained using Geant4 tools. In this case, the detector model developed in Geant4 [2] was verified by comparing the simulation and experiment results for detecting neutron and alpha radiation. The model spectra and responses of radioisotope neutron sources (252Cf, PuBe), as well as the spectra of neutrons formed during the DT reaction, are considered.
Also, in this work, the quality criteria for the unfolding of neutron spectra [3] are considered. The studies showed that the use of the response matrix obtained using Geant4 allows the unfolding of neutron spectra in the energy range from 0.1 to 15 MeV from diamond detector responses a with a difference in the unfolded and the real one spectrum less than 1%. In this case, the solution of unfolding problem remains stable in the presence of uncertainty in the input data, which is determined by the inaccuracy of the simulation or modeling results.
1. Amosov V.N., Meshaninov S.A., Rodionov N.B. and others // Diamond & Related Materials 2011. Vol. 20, P. 1239-1242.
2. Hosseini S. A., Afrakoti I.E. // Journal of Radiation Research, 2018. Vol. 59, No. 4, P. 436–440.
3. Vega Carrilo H.R., Ortiz Rodrigues J.M., Martinez-Blanco M.R. // NSDUAZ unfolding package for neutron spectrometry and dosimetry with Bonner spheres., Applied Radiation and Isotopes, 2012, Vol. 71, P. 87-91
Today calorimetry plays an important role both in experimental studies in high energy physics and in applied research. For determination of incident particles energy with higher energy resolution the digital calorimetry can be used [1]. The digital electromagnetic calorimeter includes the segmented layers and counts the total number of particles passing through the detector volume as opposed to an analogue calorimeter, which counts the total deposited energy in a given volume. In this work the new type of digital electromagnetic calorimeter, based on silicon pixel sensors has been proposed for the identification of electron beam parameters. The conception of such calorimeter was provided together with the experimental results from beam tests and GEANT Monte Carlo simulations.
The reported study was supported by RFBR, research project No. 18-02-40075.
[1] A.P. de Haas, G. Nooren, T. Peitzmann et al., “The FoCal prototype - an extremely fine-grainedelectromagnetic calorimeter using CMOS pixel sensors” JINST13 P01014, 2018
Josephson current between two one-dimensional nanowires with proximity induced either s-wave or p-wave pairing and separated by a narrow dielectric barrier in the presence of Rashba spin-orbit interaction (RSOI), in-plane and normal Zeeman magnetic fields (ZMF). A topological superconducting phase in a Josephson junction of s-wave superconductors (s-JJ) is realized under the condition $|∆|^2>B^2+h^2$, where Δ, B, and h are correspondingly the gap, Zeeman energy of in-plane and normal magnetic fields. Instead, the condition $∆_k=\frac{\vec{k}}{|k|} ∆_0$ guarantees an existence of a conducting state in the gap and realization of a generic topological phase of the p-wave superconductor (p-JJ). Andreev retro-reflection is shown to be realized through two different channels. A scattering in a conventional particle-hole channel, when an electron-like quasi-particle reflects to a hole-like quasi-particle with opposite spins, provides the current which depends only on the order parameters’ phase diﬀerences ϕ, and oscillates fractionally with 4π period. Second anomalous particle-hole channel, corresponding to the Andreev reﬂection of an incident electron-like quasiparticle to hole-like quasiparticle with the same spin orientation, survives only in the presence of the in-plane magnetic ﬁeld. The contribution of this channel to the Josephson current oscillates with 4π period not only with ϕ but also with orientational angle of the in-plane magnetic ﬁeld θ resulting in a magneto-Josephson eﬀect. Evident expressions for the effects of RSOI and ZMF on Andreev bound state energy are found in several asymptotic cases for both s-JJ and p-JJ. RSOI and ZMF are shown to split the quasi-electron and quasi-hole excitation states in the superconducting gap, and two quasi-particle and quasi-hole pairs instead of one pair appear in the gap, which are localized symmetrically around Fermi level. ZMF is shown to destroy this symmetry. Even in the absence of the magnetic ﬁelds in s-JJ the energy gap between the Andreev bound states decreases with increasing RSOI. Investigation of ac-Josephson current in s-JJ shows that the width of the resulting Shapiro steps in such a system can be tuned by varying the RSOI constant. In the presence of RSOC and normal-to-plane magnetic ﬁeld h in p-JJ, a forbidden gap is shown to open in the dependence of Andreev bound state energies on the phases ϕ and θ at several values of RSOC strength and ZMF, where Josephson current seems to vanish.The formalism that we develop here may be extended to regime of strong α and B where the presence of Majorana bound states shapes the characteristics of the Josephson current.
Film scintillation detectors 0.3-0.5 mm thick and their corresponding optical fiber are used to detect α-radiation and various nuclear reaction products.
These detectors and the used spectrometric electronics make it possible to register radiation and transmit information with a frequency of more than $10^{5}$ pulses per second and pulse duration $\leq 5$ ns.
In combination with film-based detectors, XP2020 photomultiplier tubes were used.
The film scintillation detectors were made according to Russian Technology.
The primary goal of the PHENIX experiment at RHIC is the experimental study of the quark-gluon plasma (QGP) using relativistic heavy ion collisions. In recent years, the unique set of small collision systems has provided evidence for collective flow in such systems that is driven by the initial state geometry. Hydrodynamical models, which include the formation of a short-lived QGP droplet, provide a simultaneous description of these measurements. Thermal photon measurements also indicate that the temperature achieved in the central collisions of small systems is high enough to form QGP. The scaling behavior of direct photon production in the large systems is verified by the new measurement of thermal photons using the Au+Au data set collected by PHENIX in 2014. From these measurements, multiplicities at which QGP effects turn on could be indicated. The study of particle collectivity and hard probes from large to small systems, in order to understand the bulk and fine structure of the QGP, will be discussed.
Exploration of the hot and dense nuclear matter produced in collisions of heavy ions is one of the main goals of modern relativistic nuclear physics. The Relativistic Heavy Ion Collider (RHIC) provides a unique opportunity to map the QCD phase diagram colliding different nuclei species and varying the energy of collisions. RHIC has already begun the second phase of the Beam Energy Scan (BES) program, which will allow us to cover energy range for gold-gold collisions $\sqrt{s_{NN}} = 7.7 - 27$ GeV. The Fixed-target Program (FXT) will extend collision energy range available for the analysis down to $\sqrt{s_{NN}} = 3.0$ GeV. BES-II along with FXT will dramatically enhance our understanding of the QCD phase diagram in the broad range of baryon chemical potential, $\mu_B$, up to 720 MeV.
Recent detector upgrades increase STAR's acceptance both in rapidity and low transverse momentum, and extend its particle identification capabilities. With new detectors STAR can explore phase diagram with even higher precision hopefully reaching both the onset of deconfinement as well as the onset of fireball.
In this talk, we will present the most recent results and future plans from the STAR experiment.
The research programme of the NA61/SHINE Collaboration covers a wide range of hadronic physics in the CERN SPS energy range (beam momentum 13A - 158A GeV/c), encompassing measurements of hadron-hadron, hadron-nucleus as well as nucleus-nucleus collisions. Data are analysed to better understand the properties of hot and dense nuclear matter. This talk will present the energy dependence of quantities inspired by the Statistical Model of Early Stage (kink, horn and step) as well as recent results of particle production properties in p+p and centrality selected Be+Be, Ar+Sc at the SPS energies. Moreover, the current achievements and future plans related to the measurement of open charm production will be presented.
An overview on the most recent results by the ALICE collaboration at the LHC is presented for both heavy-ion collisions (Pb--Pb and Xe--Xe) and small systems (pp and p--Pb). A broad range of topics is covered, which includes bulk particle observables and particle chemistry, heavy flavour and quarkonia production, jet-medium interaction and electromagnetic probes. Motivations and status of the ongoing upgrade of the ALICE detector are discussed.
During the ongoing Long Shutdown of the LHC, ALICE is installing detector upgrades that will allow to collect the full 50 kHz interaction rate of the LHC, collecting 2 orders of magnitude more events than in run 1 and 2. This, together with the improved track-resolution will allow ALICE to significantly improve the precision of measurements of rare signals such as heavy flavour and di-lepton production at low pt, where they probe the QGP at the scale of the temperature.
To cope with this challenge, ALICE is implementing new hardware and software solutions. The Time Projection Chamber (TPC) – the main ALICE tracking detector – has been refitted with the new GEM-based readout chambers and three new detectors are being installed: the Inner Tracking System (ITS), the Muon Forward Tracker (MFT) and the Fast Interaction Trigger (FIT) detector. The new silicon trackers are based on ALPIDE (ALICE Pixel Detector) – a custom designed sensor incorporating the requirements imposed by the physics program including a high-granularity and low material budget of the non-active elements. The new sensor will improve vertexing and tracking, especially at low pT values. The use of ALPIDE by the Muon Forward Tracker will add vertexing capabilities to the Muon Spectrometer covering a broad range of transverse momenta and allowing ALICE to measure beauty down to pT ~0 from displaced J/ vertices and to have an improved precision for the (2S) measurement. It will also add high-granularity data to the forward multiplicity information acquired by FIT. In addition to providing inputs for the new Central Trigger Processor, FIT will serve as the main luminometer, collision time, multiplicity, centrality, and reaction plane detector for the ALICE experiment.
In this presentation the main goals of the upgraded ALICE experiment and a brief status of the construction, installation and commissioning of the major ALICE detectors will be summarized. The talk will conclude with the outline of the future plans being discussed by the collaboration.
One of the main goals of the ongoing upgrade of ALICE during the second long LHC shutdown (LS2) is to signficantly improveme the charged particle tracking and secondary vertex reconstruction, as well as the readout rate capabilities of the detector system. The ALICE physics programme of measurements of low momentum charm and beauty hadrons and low-mass dielectrons in heavy-ion collisions at the LHC requires the development of an entirely new Inner Tracking System (ITS2) with the increased capabilities in readout speed, impact parameter resolution and the reduced material budget. These requirements are met in the ITS2 design by the application of arrays of novel coordinate-sensitive CMOS Monolithic Active Pixel Sensors (MAPS) with the sensor matrix and readout integrated in a single chip, named ALPIDE (ALice PIxel DEtector). Besides MAPS, large improvements of the tracking precision and efficiency of registration of particles with low transverse momentum were achieved by a large reduction of the material budget of the ITS2 in the region close to the interaction point. As a result, the record low level of 0.38% radiation length (X/Xo) per layer for each of three innermost layers is achieved, ensuring the overall improved efficiency for heavy-flavor measuremens at low pT.
The first part of the talk is devoted to the general physics motivation, requirements and status of the ITS2 preparations for the start of RUN3 at the LHC. The second part of the presentation will cover new ideas of the ALICE upgrade during the next Long Shutdown 3 (LS3) in the period 2023- 2024 and the ongoing R&D on the development of a high granularity fast detector (ITS3) which will further reduce the material to X/Xo below 0.05% per layer, will be presented. This will include the concept of the ITS3, the status of very thin ($\sim$20 $\mu$m) MAPS sensor developments as well as the ongoing studies of the extra-light-weight mechanics and gas-cooling issues.
Acknowledgement: This work was partially supported by Funds of Ministry of Science and Higher Education of the Russian Federation and by the National Research Center "Kurchatov Institute"
Heavy-ion collision experiments offer a unique opportunity to study the production of (anti-)hyperon-baryons bound systems, called (anti-)hypernuclei. ALICE at the LHC measured the production of (anti-)hypertriton analyzing data collected in Pb-Pb collisions at the two center-of-mass energies of 5.02 and 2.76 TeV. The analysis was performed by exploiting the excellent particle identification performance of the ALICE detector, by measuring the energy loss of the charged tracks in the Time Projection Chamber. In addition, the Inner Tracking System was used to separate (anti-)hypertriton's weak decay daughters from primarily produced tracks through the precise determination of secondary vertices.
The results on (anti-)hypertriton production will be discussed and compared to model predictions, based on coalescence and statistical hadronization approaches, and to experimental results obtained at lower energies. The latest results of the (anti-)hypertriton lifetime measurement will be shown as well. Plans for the future LHC Run 3, scheduled to start in 2021, with the improvements in statistics and precision will be also presented.
The CMS detector at the LHC was designed originally as a particle physics experiment but has performed exceptionally well in the high-multiplicity environment of heavy-ion collisions. Over the past decade, the CMS collaboration had delivered multiple ground-breaking results on quark-gluon plasma produced in such collision events. In this talk, I will review the recent CMS results from the Heavy Ion program, covering a wide range of topics, from bulk medium properties to tomographic probes. I will emphasize the new results from jets, heavy flavor, and quarkonia studies, and will close with an outlook for the future running and upgrades.
$\bf{A.T. D'yachenko^{1}, I.A.Mitropolsky^{2}}$
$^{1}$Emperor Alexander I Petersburg State Transport University, St.Petersburg, Russia;
$^{2}$NRC"Kurchatov Institute", Petersburg Nuclear Physics Institute, Gatchina, Russia
In the progress of the hydrodynamic approach with a non-equilibrium equation of state [1], collisions with a beryllium target of nuclei $^{12}$C at energies of 0.3-2.0 GeV/nucleon with proton emission at an angle of 3.5 degrees, which were studied at the ITEP accelerator [2], are considered. The experimental proton spectra contain a high-energy cumulative part, as well as a soft part, to which fragmentation contributes. We could describe the cumulative part of the spectra within the framework of a non-equilibrium hydrodynamic approach, taking into account the nuclear viscosity and correction for the microcanonical distribution [3]. In this work, in accordance with experimental data, our calculations are supplemented by taking into account the contribution of protons from fragments in the region of overlapping parts of colliding nuclei and in the region of non-overlapping parts on the basis of the statistical fragmentation mechanism proposed earlier in [4, 5].
$\bf{References}$
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2.B.M. Abramov et al., Phys. Atom. Nucl. $\bf{78}$, 373 (2015).
3.A.T. D’yachenko, I.A. Mitropolsky, EPJ Web of Conferences. $\bf{204}$, 03018 (2019).
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$\bf{A.T. D'yachenko^{1}, I.A. Mitropolsky^{2}}$
$^{1}$ Emperor Alexander I Petersburg State Transport University, St.Petersburg, Russia;
$^{2}$ NRC "Kurchatov Institute", Petersburg Nuclear Physics Institute, Gatchina, Russia
In progress of a hydrodynamic approach with a non-equilibrium state equation for describing heavy ion collisions [1], we consider the emission of pions both at sub-threshold energies and at the SIS (GSI) accelerator energies. The emission of pions at sub-threshold energies is possible due to the collective intra-nuclear movement of nucleons. The influence of this motion is naturally taken into account in the framework of the hydrodynamic approach, which clearly includes the multiparticle nature of colliding heavy ions. In this case, nuclear hydrodynamics must be modified by the non-equilibrium equation of state to account for the transition from the initial non-equilibrium state to the state of local thermodynamic equilibrium. In this approach, highlighting the compression stage, the expansion stage, and the freeze-out stage with the formation of secondary particles, we described experimental inclusive double differential cross sections of pion emission for collisions of different nuclei at sub-threshold energies [2, 3]. Agreement with experimental data is achieved without introducing fitting parameters. We have extended this approach to the SIS energy domain and suggest using it in research at the NICA accelerator complex under construction in Dubna.
$\bf{References}$
1 A.T. D’yachenko, K.A. Gridnev, W. Greiner, J. Phys. $\bf{G 40}$, 085101 (2013).
2.A.T. D’yachenko, I.A. Mitropolsky, Phys. Atom. Nucl. $\bf{82}$ (2019) no. 12.
3.A.T. D’yachenko, I.A. Mitropolsky, Bull. Russ. Acad. Sci. Phys. $\bf{84}$ (2020) no. 4.
The Strong nucleus-nucleus Potential (SnnP) is of principal importance for understanding nuclear molecules [1] and for the synthesis of the superheavy nuclei [2]. Nucleon density distributions are known to play a crucial role in finding the SnnP by means of the double folding model [2], [3]. The best way is to calculate the densities in a microscopic manner, i.g. by the Hartree-Fock approach [4]–[6]. However, such calculations are rather complicated and computer resources consuming.
That is why in the present work we develop a novel fast algorithm for evaluating the proton and neutron densities for spherical nuclei. The algorithm is based on five benchmarking densities coming from the Hartree-Fock approach: $^{12}\mathrm{C}$, $^{16}\mathrm{O}$, $^{36}\mathrm{S}$, $^{92}\mathrm{Zr}$, $^{144}\mathrm{Sm}$, $^{208}\mathrm{Pb}$. Each of these microscopic densities is approximated by a combination of a Woods-Saxon profile with an exponential tail having a variable (i.e. radial dependent) diffuseness (WST profile). For the nuclei with the charge number between the benchmarking ones we perform a linear interpolation of the parameters defining the WST profile.
As a test for the WST-algorithm we find the nuclear charge density distributions for several spherical nuclei and compare those with the experimental Fourier-Bessel distributions from [7]. The agreement seems to be rather good.
Then we calculate the barrier height and radii for several fusion reactions involving two spherical nuclei using the well-known M3Y nucleon-nucleon interaction. The calculated barrier parameters are compared with the experimental ones from [8]. The calculated barriers are systematically higher than the experimental ones indicating importance of the dissipative phenomena in the above-barrier collision process [5], [6].
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[4] R.Bhattacharya // Nucl. Phys. A. 913 (2013) 1–18.
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This research focused on photoneutron production determination using three different photoneutron converters BeO, LiCl, D2O. Experiment was carried out on a linear electron accelerator [1] in A. Alikhanyan National Laboratory in Yerevan, Armenia. A set of targets was irradiated by 70 MeV electron beam. Reaction rates were determined as a result of investigations. Besides experimental results, a number of simulations were also conducted using MCNP software [2] to determine reaction rates and they were compared with ones obtained from the experiment.
We have extended applications [1] of unitary clothing transformations (UCTs) [2,3] in quantum field theory. Such transformations connect the representation of “bare” particles (BPR) and the representation of “clothed” particles (CPR), i.e., the particles with physical properties. The Kharkov potential is a recent field theoretical model of nucleon-nucleon (NN) interaction that has built up in the framework of the instant form of relativistic dynamics starting with the total Hamiltonian of interacting meson and nucleon fields in the CPR. Unlike many available NN potentials each of which is the kernel of the corresponding nonrelativistic Lippmann-Schwinger (LS) equation this potential being dependent in momentum space on the Feynman-like propagators and covariant cutoff factors at the meson-nucleon vertices is the kernel of relativistic integral equations for the NN bound and scattering states. As in Ref. [4] we have employed a transition from the relativistic Lippmann-Schwinger (LS) equation for the two-body t-matrices to the so-called boosted LS one. The theoretical predictions based on the Kharkov and CDBonn potentials are compared to recent precise data for the analyzing powers $iT_{11}, T_{20}, T_{21}$ and $T_{22}$ in the pd scattering. Special attention has paid to finding from the contemporary n-p phase shift analysis [5] reliable optimum values of the adjustable parameters involved in the covariant meson-nucleon cutoff functions in momentum space.
$\textbf{REFERENCERS}$
[1] H.Kamada, A.Shebeko, A.Arslanaliev, H.Witala, J.Golak, R.Skibinski, M.Stepanova. In: Recent Progress in Few-Body Physics, eds. N.Orr, M.Ploszajczak, F.Marques, J.Carbonell, Springer (2020).
[2] I.Dubovyk, A.Shebeko, Few-Body Syst. 48 (2010) 109.
[3] A.Shebeko, Chapter I in: Advances in Quantum Field Theory, ed. S.Ketov Intech (2012).
[4] H.Kamada, A.Shebeko, A.Arslanaliev, Few-Body Syst. 58 (2017) 70.
[5] F.Gross, A.Stadler, Phys. Rev. C\textbf{78} (2008) 014005.
Hadron scattering on light nuclei at intermediate energies is a good test of investigation of both the structure of nuclei and the mechanisms of interaction. From the scattering of various hadrons, both experimentally and theoretically, proton scattering has been studied in more detail. At the same time, the study of the scattering of other particles, for example, mesons with the same kinematics, in the same nuclei, provides additional interesting information. In the same approach, we previously studied carbon and nitrogen nuclei [1].
In this work, we study the scattering of π±- and K+-mesons at intermediate energies at 9,10В nuclei in the framework of Glauber's theory. In our calculations, we used the wave function of the 9B nucleus in the 2αN-model [2], calculated with paired αα- and αN-interactions with states forbidden by the Pauli principle. In calculating the wave function, two versions of the αα interaction were used: the l-dependent αα-Ali-Bodmer potential and the deep attractive αα-potential of Buck. In both models, the αN potential with the exchange Majorana component was chosen, which leads to even-odd splitting of the phase shifts, which reproduces phases well with l = 0, 1, and 2.
To describe the state of the 10B nucleus, the wave function was used in the model of shells with an intermediate coupling [3] with the following components: − 0.418 [42] 13D1 + 0.679 [42] 13D2 − 0.481 [42] 13F .
The reaction matrix element is calculated based on the Glauber diffraction theory of multiple scattering. The Glauber operator takes into account all the multiplicities of collisions on α particles and a proton on the 9B nucleus and one- and two-fold collisions on the 10B nucleus. The differential cross section on the 9B nucleus was calculated with two variants of the wave function and it was shown how sensitive the cross section to the structure of the nucleus.
Differential scattering cross sections of π±- and K+-mesons were calculated at several energies: 135, 180, and 220 MeV. The choice of data for the energy value is related to comparing our calculations with the available calculations and experimental data on proton scattering on the same nuclei.
This work was carried out as part of the scientific project AP05132620.
Using temperature dependent nuclear potential the temperature dependence of proton emitting decay half-lives were analyzed in framework of WKB method with inclusion of quantization conditions. The temperature dependent double-folding and proximity potentials were used in calculations. In temperature independent calculations, in contrary to Prox77, very good agreement between calculated half-lives with double-folding and experiment were observed. Considering temperature dependent potentials and Q-value showed decreasing behavior of half-life with increase of the temperature.
It was proved [1] that P-even T-odd asymmetry in differential cross sections of nuclear ternary fission reactions by cold polarized neutrons with the flight of $\alpha$-particles can be represented in common case through the sum of triple ${{\sigma }_{3}}\left( \Omega \right)={{A}_{3}}\left( \theta \right)\left( {{\mathbf{\sigma }}_{n}}\left[ {{\mathbf{p}}_{LF}},{{\mathbf{p}}_{\alpha }} \right] \right)$ and quinary ${{\sigma }_{5}}\left( \Omega \right)={{A}_{5}}\left( \theta \right)\left( {{\mathbf{\sigma }}_{n}}\left[ {{\mathbf{p}}_{LF}},{{\mathbf{p}}_{\alpha }} \right] \right)\left( {{\mathbf{p}}_{LF}},{{\mathbf{p}}_{\alpha }} \right)$ scalar correlators, depending from spin ${{\mathbf{\sigma}}_{n}}$ of polarized neutron, oriented along the axis Y, momentum of light fission fragment ${{\mathbf{p}}_{LF}}$, oriented along the axis Z, and momentum of $\alpha $–particle ${{\mathbf{p}}_{\alpha }}$ emitted in solid angle $ \Omega \left( \theta ,\varphi \right))$. Coefficients ${{A}_{3}}$ and ${{A}_{5}}$ are connected with sums of quantities ${{\left( {{\mathbf{p}}_{LF}},{{\mathbf{p}}_{\alpha }} \right)}^{n}}={{\cos }^{n}}\left( \theta \right)$ with even values $\textit{n}$. For the case of $\alpha$-particle emission in plane (Z,X) when $\varphi =0$, this correlators are presented as ${{\sigma }_{3}}\left( \theta \right)\sim \sin \theta $ and ${{\sigma }_{5}}\left( \theta \right)\sim \sin \theta \cos \theta\ $ and satisfy the symmetry condition: ${{\sigma }_{3}}\left( \theta \right)={{\sigma }_{3}}\left( \pi -\theta \right)$, ${{\sigma }_{5}}\left( \theta \right)=-{{\sigma }_{5}}\left( \pi -\theta \right)$. Then investigated correlators can be expressed through the coefficient of researched above asymmetry [2]: $D\left( \theta \right)={\left[ {{\sigma }_{3}}\left( \theta \right)+{{\sigma }_{5}}\left( \theta \right) \right]}/{{{\sigma }_{0}}\left( \theta \right)}\;$, where ${{\sigma }_{0}}\left( \theta \right)$ is the differential cross section of analogous reaction with cold polarized neutrons, as $\sigma _{3,5}^{{}}\left( \theta \right)={1}/{2}\;\left[ D\left( \theta \right){{\sigma }_{0}}\left( \theta \right)\pm D\left( \pi -\theta \right){{\sigma }_{0}}\left( \pi -\theta \right) \right]$ (1). Using experimental values ${{D}^{exp}}\left( \theta \right)$ and $\sigma _{0}^{exp}\left( \theta \right)$ for target nuclei ${}^{233}$U, ${}^{235}$U, ${}^{239}$Pu and ${}^{241}$Pu [2], the values of triple $\sigma _{3}^{exp}\left( \theta \right)$ and quinary $\sigma _{5}^{exp}\left( \theta \right)$ correlations were calculated. Taking into account the mechanism of the T-odd asymmetries formation, due to the influence of quantum rotation of the compound fissile system around an axis perpendicular to its symmetry axis on the angular distribution of fission fragments and $\alpha $–particles, these correlators can be represented as $\sigma _{3}^{th}\left( \theta \right)={{\Delta }_{3}}\left( {d\sigma _{odd}^{0}(\theta )}/{d\theta }\; \right)$, $\sigma _{5}^{th}\left( \theta \right)={{\Delta }_{5}}\left( {d\sigma _{ev}^{0}(\theta )}/{d\theta }\; \right)$(2), where $\sigma _{ev}^{0}$ and $\sigma _{odd}^{0}$ are the components [1] of the differential cross section ${{\sigma }_{0}}\left( \theta \right)$, connected accordingly with even and odd orbital moments of $\alpha $-particles, and ${{\Delta }_{3}}$, ${{\Delta }_{5}}$ are the effective rotation angles of ${{\mathbf{p}}_{\alpha }}$ relative to ${{\mathbf{p}}_{LF}}$. A comparison of the correlations from formulae (1), (2) allows to find the values of the angles ${{\Delta }_{3}}$, ${{\Delta }_{5}}$ by the ${{\chi }^{2}}$-method, and using them to calculate the correlators $\sigma _{3}^{th}$ and $\sigma _{5}^{th}$. The calculated angles ${{\Delta }_{3}}$ are comparable with the angles obtained in the classical approach [2] and have a positive sign for all nuclei. At the same time, it is possible to achieve acceptable agreement between the correlators for ${}^{235}$U, ${}^{239}$Pu and ${}^{241}$Pu, however, these correlators are very different from each other for ${}^{233}$U. A reasonable agreement of $\sigma _{5}^{th}\left( \theta \right)$ and $\sigma _{5}^{}\left( \theta \right)$ is observed for all nuclei, but the sign of ${{\Delta }_{5}}$ is positive and coincides with $\Delta $ that is calculated in the framework of the classical approach [2], but when switching from ${}^{235}$U, ${}^{239}$Pu and ${}^{241}$Pu to ${}^{233}$U, the sign changes.The differences obtained above for the classical and quantum approaches of the studied T-odd asymmetries can be used in the analysis of the reliability of these approaches.
S.G. Kadmensky, V.E. Bunakov, D.E. Lubashevsky // Bull. Russ. Acad. Sci.: Phys., 2019, vol. 83, p. 1236.
A. Gagarsky et al., Phys. Rev. C. 2016. V. 93. P 054619.
S.G. Kadmensky, L.V. Titova, V.E. Bunakov//Phys. Atom. Nucl. 82, 239 (2019).
In experimental papers [1, 2] the yields, angular and energy distributions of the pairs of light third and fourth particles formed with the highest probability, such as $\alpha$-particles pair $(\alpha_1,\alpha_2)$, were obtained for the spontaneous quaternary fission of the nucleus $^{252}$Cf. Using the theoretical concepts [3-5] of ternary and quaternary fission as virtual processes [6], we consider spontaneous quaternary fission from the ground states of even-even actinides [1,2] with the sequential emission of two $\alpha$-particles from the virtual states of nuclei $A$ and $(A-4)$ and the subsequent binary fission of the residual fissile nucleus $(A-8)$ into light and heavy fission fragments. These $\alpha$-particles, in contrast to the $\alpha$-particles that fly out in the sub-barrier $\alpha$-decay of the studied nuclei $A$ and $(A-4)$, when the energies $Q_{\alpha_1}^A$ and $Q_{\alpha_2}^{(A-4)}$ of this decays are close to 6 MeV, are long-range, since their asymptotic kinetic energies $T_{\alpha_1} \approx 16 $ MeV and $T_{\alpha_2} \approx 13 $ MeV, are markedly larger than energy values $Q_{\alpha_1}^A$ and $Q_{\alpha_2}^{(A-4)}$. Using the formula [4] for the width $ \Gamma_{\alpha_1\alpha_2 f}^A$ of the virtual quaternary fission of nucleus $A$, formulae for the widths $ \Gamma_{\alpha_1}^{A}(T_{\alpha_1})$ and $ \Gamma_{\alpha_2}^{(A-4)} (T_{\alpha_2})$ for $\alpha$-decays of nuclei $A$ and $(A-4)$ are constructed:
$
\Gamma_{\alpha_1}^{A}(T_{\alpha_1})=2\pi W_{\alpha_1}(T_{\alpha_1}) (Q_{\alpha_1}-T_{\alpha_1})^2;
\Gamma_{\alpha_2}^{(A-4)}(T_{\alpha_2})=2\pi W_{\alpha_2}(T_{\alpha_2}) (Q_{\alpha_2}-T_{\alpha_2})^2;
$
where $W_{\alpha_1}(T_{\alpha_1})$ and $W_{\alpha_2}(T_{\alpha_2})$ are the energy distributions of the first and second $\alpha$-particles, normalized by the ratio of the widths of these $\alpha$-particles emission to the width of the binary fission of the nuclei $A$ and $(A-4)$. The widths $\Gamma_ {\alpha_1}^{A}$ and $ \Gamma_{\alpha_2}^{A-4}$ take into account the fact that the emitting $\alpha$-particles are formed in such configurations of the fissile nuclei $A$ and $(A-4)$ that occur during their deformation motion from the ground states through the internal and external fission barriers and reach a pear-shaped forms corresponding to the appearance of two deformed fission prefragments connected by a neck. If we consider the ratio $ \Gamma_{\alpha_1}^{A}/\Gamma_{\alpha_2}^{(A-4)}=\sqrt{T_{\alpha_1}}P_1(T_{\alpha_1})/
\sqrt{T_{\alpha_2}}P_2(T_{\alpha_2})$ and take into account the fact that the probabilities of formation of the $\alpha_1$ and $\alpha_2$ particles are close to each other, and the radii of the neck of the nucleus $r_{A}$ before the emission of $\alpha_1$-particle does not differ much from the radius of the neck $r_{A-4}$ before the emission of the $\alpha_2$-particle, one can get the ratio of the Coulomb barrier penetrabilities $P_2(T_{\alpha_2})/P_1(T_{\alpha_1})$ for the first and second $\alpha$-particles. Using the experimental values of the kinetic energies $T_{\alpha_1}$ and $T_{\alpha_2}$ and maximum values of energy distributions $W_{\alpha_1} (T_{\alpha_1})$ and $W_{\alpha_2} (T_{\alpha_2} )$, the specified estimation of $P_2(T_{\alpha_2})/P_1(T_{\alpha_1})$ is 0.03 for spontaneous quaternary fission of $^{252}$Cf. This estimation $P_2(T_{\alpha_2})/P_1(T_{\alpha_1})$ demonstrates that the virtual decay of nucleus $(A-4)$ with $\alpha_2$ particle flight has subbarrier character in contrast to the virtual decay of nucleus $A$ with $\alpha_1$ particle flight.
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During the past few years, we have measured the angular distributions of fragments in neutron-induced fission of a number of isotopes at energies of 1–200 MeV. The studies were performed at the NRC “Kurchatov Institute” – PNPI using a TOF neutron spectrometer GNEIS at the 1 GeV proton synchrocyclotron (see [1] and references therein). Now we are adding to previously studied nuclei 209Bi, Pb (nat), 232Th, 233U, 235U, 238U, 237Np, 239Pu (see [2] and references therein) the isotope 240Pu. For energies above 20 MeV, the results are obtained for the first time, their analysis is presented in a separate report. In the region of intermediate energies exceeding 20 MeV, similar data on the angular anisotropy of fission fragments of 232Th, 235U, 238U nuclei were also obtained in [3-6].
We developed a method for theoretical description of the angular distribution of fragments as function of the energy of incident neutrons. Our approach is based on the use of the modified TALYS program [7] and is applicable in a wide range of energies, including the interval of 1–200 MeV. In [2] the results of calculations were presented for the 237Np (n,f) reaction. It was shown that even with the use of some simplifying assumptions; the method correctly describes the gross structure of the energy dependence of the angular anisotropy of fission fragments.
In this work, we apply our method to the theoretical description of the angular anisotropy of fission fragments of even-even nuclei 232Th, 238U, 240Pu by low and intermediate-energy neutrons. The first two isotopes are of particular interest. First, in the intermediate energy region, we use not only our data, but also the results of other authors [3-5]. Secondly, just for 232Th and 238U, only an estimate [3] of the energy dependence of angular anisotropy above 20 MeV was previously performed. Generally, our results confirm that data on the angular anisotropy of fission fragments are a valuable source of information on both the transition states at the barriers and the role of pre-equilibrium processes.
This work was partially supported by the Russian Foundation for Basic Research (Grant No. 18-02-00571).
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Asymmetric fission of mercury nuclei was initially observed in low energy region [1-3]. Sub-lead region is the region where it is noticed that the fission fragment shell property is over-ruled by the ridges and valleys present from saddle to scission point in the potential energy surface. These ridges and valleys are the result of shell correction, which vanishes with increase in excitation energy. In recent years several experiments have been performed in this direction to investigate the asymmetric behaviour of Hg nuclei which supported the influence of shell effects on the asymmetric fission process [4-6].
Spherical shells are more stable towards asymmetric fission in comparison to deformed nuclei. It has been observed that the three odd nuclei 181,183,185Hg have highly deformed charged radii in comparison to other mercury isotopes, due to quadrupole and monopole moment [7]. Thus, one may expect for 183Hg to show more asymmetry in fission fragments mass-energy distribution in comparison to 182Hg.
An experiment is performed using CORSET [8] setup, where we investigate mass and energy distributions of fragments and fission characteristics of oblately deformed 182 Hg (β2 = 0.147) and prolate deformed 183Hg (β2 = 0.313) nuclei formed by 40Ca+142,143Nd, at three different lab energies Elab= 172, 192, 212 MeV. Observing their β2 value we understand that 182Hg is lightly deformed in comparison to 183Hg.The energies taken into consideration are at different difference from the Coulomb barrier, so that we can study the behaviour in different regions. We are expected to get higher asymmetry for 183Hg but we find a contradicting result where there is no huge variation in mass-energy distribution of 182Hg and 183Hg at any of the measured energies. This gives us an outlook regarding influence of shell structure, charge radii deformation and factors associated in the potential energy surface that are responsible for fission in Hg region.
This work was supported by the Indian Department of Science and Technology (DST) associated with the Russian Foundation for basic Research (Grant No. 19-52-45023).
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(2008)
Mass distribution of the fission fragmnets of $^{234}$U fission by neutrons can be described using three fission modes: S1 (Standard 1), S2 (Standard 2) and SL (Super Long). Yields of these modes can be calculated using the form of the potential barriers along three different paths in the configuration space of nuclei deformation. Vibrational resonance at neutron energy about 0.7 MeV influence the cross section and angular distribution of fission fragments at this energy. We test the hyphothesis that the resonance is occurring only for one fission mode after the bifurcation. The result of the calculation are comparing with experimental data of work [1] about mass distribution of fission fragments.
Studies of production and properties of nuclei near the stability boundary with respect to neutron emission are an important part of modern nuclear spectroscopy (see, e.g., [1]). In fission of actinide nuclei, neutron-rich nuclei are produced (especially in short-lived light fragments formed in asymmetric fission at low energies of bombarding particles). In small part of beta-decays of these fragments-precursors (with values of their half-lives T1/2) highly excited states of daughter-nuclei are populated, for which in some cases it may be possible to emit delayed neutrons. Usually, for convenience of description, several groups of nuclei-precursors are introduced according to their T1/2 values of which until now have been not less than 0.2 s [2, 3]. But for an adequate description of critical systems (e.g., their reactivity) it is very important to look for precursors with T1/2 down to ~1 ms [3].
In our previous work [4] the measurement was performed from 4.5 ms after the beam pulse. And it seemed that for photofission of 238U at Eg max about 10 MeV there is indication for existence of short-lived nuclei-precursors with T1/2 ~ 1 ms. In the present work we continued studies in this direction.
Measurements were made at the pulsed linear electron accelerator LUE-8-5 of the INR RAS [5] at the energy of incident electrons Ee about 10 MeV and beam repetition rate 100 Hz. The scintillation fast neutron spectrometer with pulse shape discrimination of background g-quanta (see [6] and references therein) was used. The controlled divider of photomultiplier tube of the scintillation detector [7] had to be used to decrease negative influence of big light output near the beam pulse time. Delayed neutrons and g-quanta were registered in interval from 1.5 ms after beam pulse to 9 ms with average beam currents about 16 nA.
The statistical uncertainties of the data, obtained so far in this way, do not allow us to distinguish existence of nuclei-precursors of delayed neutrons with T1/2 ~ 1 ms.
References:
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Alpha cluster structure in 19F
Nauruzbayev D.K.1,3, Nurmukhanbetova A.K.1 , Goldberg V.Z. 2
1 Energetic Cosmos Laboratory,Nazarbayev University, Nur-Sultan, 010000,Kazakhstan,
2 Cyclotron Institute, Texas A&M University, College Station, Texas, USA
3 Saint Petersburg State University, Saint Petersburg, Russia
E-mail: anurmukhanbetova@nu.edu.kz
The nucleosynthesis of 19F was investigated over the past several years 1. The synthesis of fluorine occurs by 14N(α,γ)18F(β+)18O(p, α)15N(α,γ)19F reaction chain in the asymptotic giant branch stars [1-2]. For that reason, the studies of the abundance of 19F can be useful as a probe of stellar nucleosynthesis [1,3].
Several experimental groups also have been studied the properties of levels in 19F nuclei [1,4,5]. The aim of these studies was the knowledge of cluster structure in N>Z nuclei. Still, the information on the alpha cluster structure of 19F is scarce because of the experimental difficulties of the studies of elastic scattering of alpha particles at a gas target at low energy in the backward hemisphere [4].
We made the measurements of the 15N+α elastic scattering using the Thick Target Inverse Kinematic [6] method in a broad angular range including 180 degrees in c.m.s. at heavy ion accelerator DC-60 [7-8] (Nur-Sultan, Kazakhstan) and analyzed the available experimental data using R-matrix formalism [9]. This study presents a comprehensive analysis of the experimental data and reveals an interesting relation between level structure in 19F and 20Ne.
Fig.1. demonstrates the quality of the new fit for θc.m. = 149.5 [4] in the energy range 2.0-4.4 MeV.
Acknowledgments:
Authors acknowledge financial support from the Nazarbayev University [small grant number 090118FD5346], the Ministry of Education and Science of the Republic of Kazakhstan [state-targeted program number BR05236454] and [young scientists’ research grant number AP08052268].Nauruzbayev D.K. is thankful for support from RFBR, research project No. 20-02-00295
References:
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The strongly intense quantities and robust variances in processes of multi-particle production in pp and AA interactions at LHC energies was studied. The Monte Carlo and analytic modelling of these quantities in the framework of a quark-gluon string model were implies. The string fusion effects were also taken into account by implementing of a lattice (grid) in the impact parameter plane. Strongly internsive variable $\Sigma(n_F,\ n_B)$ was calculated for different energies for two values of the width of the observation rapidity windows as a function of the distance between the centers of this windows.
Scaled variance $\omega_n$ and robust variance $R_n$ for different energies and for different width of the observation rapidity window was calculated by MC simulations. Strongly internsive variable $\Sigma(n_F,\ n_B)$ calculated from MC simulation results was also compared with preliminary ALICE experimental data.
This talk is based on CERN Summer Student Project [1].
[1] Belokurova Svetlana, Study of strongly intense quantities and robust variances in multi-particle production at LHC energies, CERN-STUDENTS-Note-2019-021, (2019); CDS: https://cds.cern.ch/record/2684671
The Large Hadron-electron Collider is the proposal of an upgrade of the HL-LHC. An energy recovery linac will provide 50 GeV electrons to collide with the HL-LHC hadrons beams or, later, with the hadron beams at the Future Circular Collider. When combined with the available HL-LHC Pb beams, it will deliver e-Pb collisions with nucleon-nucleon centre-of-mass energies around 0.8 TeV, and per nucleon instantaneous luminosities around $10^{33}$ cm$^{-2}$s$^{-1}$. Such collisions will explore a completely uncharted region of the $x-Q^2$ plane that extends the region presently covered by nuclear DIS experiments by three to four orders of magnitude in $x$ and $Q^2$. In this talk we present the physics opportunities with such machine: a determination of nuclear parton densities with complete flavour unfolding, studies of 3D structure using diffractive observables, and the opportunities to search a new non-linear regime of QCD - parton saturation - through combined studies of e-p and e-A collisions. Besides, studies of QCD radiation and hadronisation in the nuclear environment. All these aspects have strong implications of our understanding of heavy ion collisions at high energies and of the quark-gluon plasma.
Based on the quark-hadron duality concept the hadronization of the deconfined matter arising in high-energy particle collisions is considered. The number of generated hadrons is shown to be entirely determined by the exact non-equilibrium Green's functions of partons in the deconfined matter and the vertex function governed by the probability of the confinement-deconfinement phase transition.
Compactifying the standard (3+1) chromodynamics into $ QCD_{xy} + QCD_{zt}$, the rate of hadrons produced in particle collisions with respect to both the rapidity and $p_T$ distributions is derived in the flux tube approach. Provided that the hadronization is the first order phase transition, the hadron rate is derived in the explicit form. The obtained rate is found to depend strongly on the energy of the colliding particles, number of tubes, hadron mass as well as on the temperature of the confinement-deconfinement phase transition. In the case of the pion production in $pp$ collisions we obtain a good agreement to the experimental results on the pion yield with respect to both the rapidity and $p_T$ distributions.
In a chirally-imbalanced medium we compare some constraints on parameters both in the linear sigma model (LSM) and in the chiral perturbation theory (ChPT) as realizations of low energy quantum chromodynamics (QCD) for light mesons. The relations between the low-energy constants of the chiral Lagrangian and the corresponding constants of the linear sigma model are established as well as the expressions for the decay constant of the pion and the mass of the $ a_0$ mesons in chiral medium are found. A possible experimental detection of chiral- imbalance medium (and therefore a phase with Local Parity Breaking) potentially can be found in the charged pion decays inside the fireball.
The talk is devoted to QCD phase diagram studies, including the region of large baryon density that will be probed at NICA.
Part of the talk is
based on:
Phys.Rev. D95 (2017) no.10, 105010
Phys.Rev. D97 (2018) no.5, 054036
Phys.Rev. D98 (2018) no.5, 054030
Eur.Phys.J. C79 (2019) no.2, 151
JHEP 1906 (2019) 006
Phys. Rev. D 100, 034009 (2019)
Recently It has been shown that in the large-Nc limit (Nc is the number of colors of quarks) there exist duality correspondences
(symmetries) in the phase portrait, which are the symmetries of the thermodynamic potential and the phase structure
itself. The first one is a duality between the chiral symmetry breaking and the charged pion condensation
phenomena. And there are two other dualities that hold only for chiral symmetry breaking and charged pion condensation phenomena separately. For example, we have shown that charged pion
condensation does not feel the difference between chiral and isospin imbalances of the medium. They were shown to exist in the matter with chiral imbalance that can be produced in compact stars or heavy
ion collisions. One of the key conclusions of these studies is the fact that chiral imbalance generates charged pion
condensation in dense baryonic/quark matter. It was shown that our results in particular cases are consistent with the simulation of lattice QCD, which is possible in these cases.
Duality was used to show that there takes place catalysis of chiral symmetry breaking by chiral imbalance.
It was also shown that chiral imbalance generates the phenomenon of charged pion condensation in dense baryonic/quark matter even in the case of charge neutral matter, which is interesting in the context of the astrophysics of neutron stars.
It is known that chiral imbalance can occur in high energy experiments of the collision of heavy ions, due to
temperature and sphaleron transitions. Our studies show that different types of chiral imbalance can occur in the cores of neutron stars or in heavy ion experiments, where large baryon densities can be reached, due to another phenomena - the so-called chiral separation and chiral vortical effects.
Duality was shown to exist even in case of inhomogeneous condensates. This example shows that the duality is not just entertaining mathematical property but an instrument with very high predictivity power.
The unified picture and full phase diagram of isospin imbalanced dense quark matter have been assembled. Acting on this diagram by a dual transformation, we obtained, in the framework of an approach with spatially inhomogeneous condensates and without any calculations, a full phase diagram of chirally asymmetric dense medium.
Continuing our studies of dualitiesl, we noted that there are dualities in 2-color QCD that are connected with adiitional symmetry of QCD with two colors namely Pauli-Gursey symmetry.
It has been also shown that found duality is a more fundamental and can be shown at the level of Lagrangian. It has been shown that duality is a property of real QCD. It is not bounded by large Nc approximation and exists in the cases of 2 and 3 and infinite number of colours.
A search for the time-noninvariant (T-odd) interactions is one of the most fundamental not yet resolved problems in physics and, more generally, in nature. In 1950, Purcell and Ramsey [1] suggested that it is equivalent to the search for the electric dipole moment(EDM) of any elementary particle. The existence of EDM violates both P- and T-invariance (P is the space parity). The search for the EDMs continues already for 50 years without any success. In [2-3] it was predicted that in heavy diatomic molecules, the electron EDM ($e$EDM,$d_e$) can be greatly (up to $10^9$ times) enhanced. The other possible P,T-odd effect in atomic systems - scalar-pseudoscalar interaction of an electron with atomic nucleus in an external electric field can be always presented as an existence of ''equivalent'' $e$EDM $d_e^{\text{eqv}}$ [3]. The most advanced recent experiment on the observation of $e$EDM in the ThO molecule (ACME collaboration, USA) sets the upper bound for $e$EDM $d_e<1.1\times 10^{-29}$ $e$ cm ($e$ is the electron charge) [4]. The accurate evaluation of $e$EDM within the standard model (SM) is still absent, the maximum estimated value is $d_e \sim 10^{-38}$ $e$ cm [5]. No signs of ``new physics'' inside this gap of 9 orders of magnitude between the theory and experiment are not yet found. This encourages to suggest the new, more sensitive methods for observation of $e$EDM in atomic physics. Such a suggestion was made in [6-7] where the P,T-odd Faraday effect (rotation of the polarization plane for the light propagating through a medium in presence of an external electric field) was considered. The experiment was assumed to be performed with the modern ICAS (intra-cavity absorption spectroscopy) techniques which made important successes during the last decades [8]. Theoretical simulations of such experiments together with accurate calculations of the molecular structure showed that the sensitivity of the P,T-odd Faraday experiment on the PbF molecule can exceed the sensitivity of ACME experiment by 6-7 orders of magnitude. An advantage of the P,T-odd Faraday experiment is that the P,T-odd effect is cumulated on the light, while in ACME experiment (electron spin precession in an external electric field) it is cumulated on molecules. To surpass the shot-noise limit (which is the main condition to reach the higher sensitivity) it is much easier to have larger number of photons than the larger number of molecules. Then, using the nonlinear optical effects one may hope to close fully the gap between experiment and SM theory for $e$EDM.
[1] E.M. Purcell, N.F. Ramsey, Phys. Rev. \textbf{78}, 807 (1950)
[2] O.P. Sushkov and V.V. Flambaum, ZhETF \textbf{75}, 1208 (1978)
[Sov. Phys. JETP \textbf{48}, 608 (1978)]
[3] V.G. Gorshkov, L.N. Labzowsky and A.N. Moskalev, ZhETF \textbf{76}, 414 (1979)
[Sov. Phys. JETP \textbf{49}, 209 (1979)]
[4] V. Andreev et al. (ACME collaboration), Nature \textbf{562}, 355 (2018)
[5] M. Pospelov, I. Khriplovich, Sov. Nucl. Phys. \textbf{53}, 638 (1991)
[6] D.V. Chubukov, L.V. Skripnikov, V.N. Kutuzov, S.D. Chekhovskoi, L.N. Labzowsky, Atoms \textbf{7}, 56 (2019)
[7] D.V. Chubukov, L.V. Skripnikov, L.N. Labzowsky, JETP Letters \textbf{110}, 382 (2019)[Pis'ma v ZhETF \textbf{110}, 363 (2019)]
[8] M. Durand, J. Morville, D. Romanini, Phys. Rev. A \textbf{82}, 031803 (2010)
Single-photon emission computed tomography (SPECT) is a well known imaging method of nuclear medicine, which allows obtaining tomographic images of the biodistribution of radiolabeled compounds, both throughout the patient’s body and in separate organs. At the same time, a small animal SPECT is currently a key tool in the development of new radiopharmaceuticals and to seek for methods for their targeted delivery. However, in studies of small animals, the region of interest typically has a small size and a high spatial resolution is necessary to get a good image. A system based on the coded aperture and the hybrid pixel Timepix detector with the CdTe sensor is developed as a possible imaging solution for the small animal SPECT. Characterization of the system using an X-ray source and various radioactive gamma emitters, including Tc-99m and I-125, is made. The spatial resolution is shown to be of 0.8-0.9 mm at the field of view of 3 cm x 3 cm for the energy range typical for SPECT. The experimental data, supported by the simulation, confirm that a 1 mm thick tungsten coded aperture is sufficient to obtain an image of the distributed radioactive sources with the energy of gamma rays at least up to 180 keV without significant reconstruction artifacts. The reconstructed tomographic images of a SPECT phantom are presented.
A system of three low threshold-energy ion-chambers, giving new possibilities
in proton beam monitoring and analyzing, is considered. The system includes a new double-gap chamber with the total gap of 1mm, with polyimid films of 3\,$\mu m$ thickness and with the sensitive area 113-\,$cm^2$ and two double-gap ion-chambers, each with the total gap of 2 mm. Ionization losses in each of six sensitive air gaps, as well as the total loss, are measured in coincidence for every accelerator spill. Total amount of material crossed by the beam is only 1.7 $g/cm^2$. Being almost transparent for protons at Bragg-peak energy and below, the anode separates two neighbour gaps and peculiar behavior of loss correlations can be observed. This behavior can be explained by alternative trend of energy-loss dependence below and above Bragg peak. Recombination contribution is estimated as only few percents at 1 $nA/cm^2$. An essential contribution to the dose from protons at about 1 MeV and below was demonstrated both by calculations and experimental data. Selected contributions of fast and slow protons and $\delta$ electrons to the energy loss can be extracted from data. The system demonstrated a stable operation after a proton irradiation of 5 Mrad.
INVESTIGATION OF EXPOSURE OF EPITHERMAL NEUTRONS RADIATION ON THE SAMPLES OF TUMOR TISSUES AT Gd-NCT
Kulabdullaev G.A.1, Kim A.A.1, Abdullaeva G.A.1, Djuraeva G.T.1, Yuldashev D.O.1, Mavlyanov I.R.2, Kadyrbekov R.T.3, Kadyrbekov N.R.3, Beknazarov H.J.3
1 Institute of Nuclear Physics, Academy of Sciences of Uzbekistan,
2 Tashkent Medical Academy, Ministry of Health, Uzbekistan
3 Republican Scientific Center of Neurosurgery, Ministry of Health, Uzbekistan
The purpose of the study was to assess the impact of radiation exposure of epithermal neutron and epithermal neutrons with gadolinium neutron capture reaction on the samples of brain tumor tissues.
For the experiments were carried out calculations for neutron capture reaction of gadolinium. Natural gadolinium is composed of seven isotopes, of which 155Gd and 157Gd have very large (n,) cross-section, are respectively 255,000 and 60,000 barns Therefore, these isotopes, which are> 30% natGd, are the most effective isotope for neutron capture. For natGd thermal neutron capture cross section is equal to 49,000 barns, whereby natGd is one of the widely used elements in neutron capture therapy.
To create the required absorbed dose in tumor tissue sample the different concentrations of gadolinium are used, which can be adjusted by diluting the starting preparation of Magnevist. The concentration of gadolinium in Magnevist is 65.916 mg/g (65.916 ppm).
In the reaction of epithermal neutron beam with biological tissue elements the release of energy takes place as a result of nuclear reactions and absorption of the secondary gamma-ray quanta. The nuclear reactions produce the charged particles and recoil nuclei having a short run, and their energy is absorbed in the layers with several tens of microns thick. Secondary gamma rays quanta have energies up to ~ 10 MeV, and their run is a few tens of centimeters. Therefore, calculation the dose in biological tissue requires knowledge of the full spectrum of gamma rays and the partial kerma dependence on neutron energy and the gamma rays quanta for all elements of the biological tissue. Kerma, a close analogue of the absorbed dose, at known neutron spectrum was determined by the method published earlier [1]. The database EPAPS [2] was used for calculation for partial neutron kerma depending on energy of elements, composing of biological tissue.
Investigations were carried out on the samples of human glioma tumor tissues extracted during standard surgical operation. From tumor tissue samples the living slices were prepared and placed in culture medium. Prepared living slices were used for epithermal neutron beam irradiation with different absorbed doses in the presence of gadolinium-containing preparation Magnevist (gadopentetata dimeglyumin) or without it. After irradiation, the slices of samples were incubated saline with 5% glucose for 24 hours at 4C. After incubation, slices were fixed in 10% formalin and histological analysis was performed for estimation of degree of tumor tissue necrosis. The findings allow to obtain accurate estimate the degree of necrosis of the tumor tissue after irradiation with different absorbed dose and at irradiation by epithermal neutrons and irradiation by epithermal neutrons with particles produced during the gadolinium-neutron capture reaction.
The authors proposed a development strategy for combined radiation methods for sterilization of bone implants in order to increase their effectiveness in clinical use [1]. The relevance of this work is determined by the ever-increasing need for plastic material during reconstructive operations in bioimplantology [2]. Recent works have confirmed the promise of combined sterilization methods [3], which are based on the use of the advantages of radiation exposure on bone implants in combination with preliminary ozone treatment, which reduces the radioresistance of pathogenicity. The synergistic effect achieved in this case provides effective sterilization with a significant reduction in the absorbed dose and side effects of each of the acting factors separately [4].
Particular attention is paid to the development of objective methods for assessing the quality of implants, indirect control of the initial osteoinductive and osteoconductive properties, the structural and functional state of the surface layer with the determination of its elemental composition. The condition and surface characteristics of the bone implant largely determine its osteinductive and osteoconductive properties, regenerative potential and, thus, the effectiveness of application in bioimplantology [5].
The properties and mass distribution of the ultramagnetized atomic nuclei which arise in heavy-ion collisions and magnetar crusts, during Type II supernova explosions and neutron star mergers are analyzed. For the magnetic field strength range of 0.1–10 teratesla, the Zeeman effect leads to a linear nuclear magnetic response that can be described in terms of magnetic susceptibility [1]. Binding energies increase for open shell and decrease for closed shell nuclei. A noticeable enhancement in the yield of corresponding explosive nucleosynthesis products with antimagic numbers is predicted for iron group and r-process nuclei. Magnetic enrichment in a sampleof 44Ti corroborate theobservational results and imply a significant increase in the quantity of the main titanium isotope, 48Ti, in the chemical composition of galaxies. The enhancement of small mass number nuclides in the r-process peak may be due to magnetic effects.
[1] Kondratyev, V.N.. Phys. Lett. B, 782 (2018) 167
Double core hole (DCH) states enclose two vacancies in the electronic K-shell of atoms and molecules. This object currently attracts close attention and DCHs might become a new tool for chemical analysis [1] and plasma diagnostics [2]. DCHs are efficiently created by high-brilliance X-ray free-electron lasers in double ionization by two sequentially absorbed $\gamma$-quanta [3]. On another side, the DCHs were first detected many years ago in the process of K-electron capture by an atomic nucleus [4], when the nuclear charge is reduced by unity, and the second electron is shaken-up from the K-shell mostly due to the sudden change of the atomic potential. Using bright synchrotron radiation sources, the DCHs are observed in photoabsorption of the X-ray photon by the K-shell electron, with simultaneous shake of the second K-electron [5], similar, in a sense, to the case of the K-electron capture, but with the nuclear charge remaining the same.
In this theoretical contribution we compare the two mechanisms of producing the DCH: K-electron capture and K-shell photoionization. General theoretical approaches to both problems are known, but we are not aware of such a comparison, based on up-to-date models for many-electron atoms. We also believe that theoretical predictions for the shake process in the K-capture, made decades ago, may be improved by using these models. Here we focus on the DCH states in ^{7}Be and ^{37}Ar isotopes with natural electron capture radioactivity and determine the relative DCH production probability P_{KK}. Furthermore, we analyze the relative probability of shake-up and shake-off, when the second K-electron is excited to a discrete state or is ionized, respectively. The shake-off electron spectra in the K-capture are obtained and compared with the results of different theoretical approaches and experiment. The photoionization calculations were performed by the R-matrix method with B-splines, as realized in the BSR package [6]. The non-orthogonality between electron wave functions in the initial and final states, which is crucial in treating ionization from the inner shell, was fully taken into account. The electron wave functions for the bound states were obtained in the multi-configuration Hartree-Fock approximation. The model for the K-capture is based on conventional sudden approximation and is utilizing codes from the same BSR package. Detailed results will be presented at the conference.
Collisions of metastable antiprotonic helium atoms with the medium atoms induce, inter alia, transitions between hyperfine structure (HFS) states, as well as shifts and broadening of microwave M1 spectral lines. These effects were studied in the experiments with the low-temperature $^4\mathrm{He}$ [1,2] and $^3\mathrm{He}$ [3] targets, and were considered in the framework of the model interaction between $(\mathrm{\bar{p} He}^+)$ and $\mathrm{He}$ [4,5]. In this work, interaction between thermalized antiprotonic $(\mathrm{\bar{p}}^4\mathrm{He}^{+})$ atom and ordinary $^4\mathrm{He}$ atom is described by an ab initio potential energy surface (PES) calculated in the framework of unrestricted Hartree-Fock method with account for electron correlations in the second-order perturbation theory (MP2). With this PES, the system of close-coupling equations for HFS channels is solved numerically. Cross sections and transition rates, shifts and broadening of M1 spectral lines are calculated. They are used to obtain a numerical solution of the master equation that determines the time evolution of the HFS-states density matrix. The results are compared with the experimental data and with the model calculation.
1. T.Pask, D.Barna, A.Dax et al., J. Phys. B: At. Mol. Opt. Phys. 41, 081008 (2008).
2. T.Pask, D.Barna, A.Dax et al., Phys. Letters B 678, 55 (2009).
3. S.Friedreich, D.Barna, F.Caspers et al., J. Phys. B: At. Mol. Opt. Phys. 46, 125003 (2013).
4. G.Ya.Korenman and S.N.Yudin, Hyperfine Int. 194, 29 (2009).
5. G.Ya.Korenman and S.N.Yudin, J. Phys. B: At. Mol. Opt. Phys. 39, 1473 (2006).
The investigation of distribution of charge density of nuclei by means of electronic scattering have begun from Hofstadter work series [1–2]. Further many important works were made in this field [3–5]. Here I present specific models of charge distribution with symmetrized Fermi distribution in the center of nuclei and small perturbation on periphery used for fitting electron scattering data by Born approximation method. I have chosen the local functions as perturbations (will be discussed in the report). In this work I consider only light even-even nuclei with N=Z, so called alpha-particle nuclei.
In my opinion the most interesting result of the paper is decreased level of significance for applied in this work hypotheses for nuclei lighter then O-16. It seems very realistic to use such charge distributions for Mg-24, Si-28, S-32.
Also in my report, I am going to consider reliability of applications of various charge distributions for analysis of electronic scattering data that exist today.
[1] R. Hofstadter, Rev. Mod. Phys. V 28, N 3, July, 1956
[2] R. Hofstadter, Ann. Rev. Nucl. Sci. 7, 231 (1957).
[3] Yennie D.R., Boos F.L., Ravenholl D.C. HPhys. Rev.1965. V. 137. P. B882
[4] Variations analysis in the charge density distribution in nuclei, Burov V.V., Kadrev D.N., Lukyanov V.K., Pol’ Yu.S. Dubna, 1976 (Анализвариацийраспределенияплотностизарядавядрах / В. В. Буров, В. К. Лукьянов, Ю. С. Поль. - Дубна : [б. и.], 1976)
[5] Burov V.V., KadrevD.N., Lukyanov V.K., Pol’ Yu.S. // Phys. Atom. Nucl. 1998. V. 61. P. 525.
On the basis of the Hartree-Fock-Bogolyubov (HFB) method with various versions of Skyrme forces we investigated the position of the neutron drip-line (NDL) of Ca isotopes with allowance for axial deformation of nuclei. For calculations of the properties of the ground state of even-even isotopes of Ca, we used computer code HFBTHO v2.00d [1] and our software package as in [2]. Our calculations and those of various authors [3] have shown that the position of the NDL for different types of Skyrme forces differs significantly in the boundary value of the number of neutrons $N_{drip-line}$. We have shown that for the same type of Skyrme forces, the determination of the $N_{drip-line}$ is also ambiguous. We performed constrained HFB calculations of the total energy of Ca isotopes in the vicinity of the NDL depending on the quadrupole deformation parameter $\beta_2$ in the range of $-0.5\leq\beta_2\leq0.5$. It is shown that for the isotopes $^{68}$Ca (forces UNEDF1) and $^{66}$Ca (forces SLy4) over the entire range of considered $\beta_2$, in the vicinity of the min curve E($\beta_2$), the chemical potential of the nuclei is $\lambda_n<0$. These isotopes can be considered as neutron-stable. For the isotopes $^{70}$Ca (forces UNEDF1) and $^{68}$Ca (forces SLy4) in the vicinity of the min curve E($\beta_2$), the chemical potential of the nuclei is $\lambda_n>0$. If we consider the condition $\lambda_n<0$ as a condition for the stability of the nucleus with respect to the emission of one neutron, then the nucleus $^{70}$Ca (for forces UNEDF1) and $^{68}$Ca (for SLy4 forces) cannot be considered as neutron-stable. In [3], these nuclei are given as neutron-stable for which the separation energies of one neutron have positive values.
Nowadays all the elements up to 118th are known due to success of experimental nuclear physics in new heavy element synthesis [1], however, not all the masses of new nuclides have been measured. In our work, the phenomenological approach based on local mass relations is implemented to predict masses of unknown isotopes. This approach is characterized by mathematical simplicity and accuracy [2], especially when it is concerned with mass relations for residual proton-neutron interaction [3, 4]. In the region of heavy and superheavy elements the behavior of various mass relations associated with nucleon correlations is considered. Estimations of nuclides’ masses and α-decay energy values for elements with Z=107-110 are gained by approximation of these mass relations. The results are compared with calculations using other approaches [5-7] and also with the machine-learning based calculations.
In $[1]$ we have investigated the cross sections of the $^{13}C(d,p \gamma)^{14}C(3^–$; 6.73 MeV) reaction at $E_d$ = 15.3 MeV. In this article the double-differential cross sections of the same reaction were measured for six proton emission angles on the SINP MSU 120-cm cyclotron. The angular correlation functions $W(θ_\gamma, \varphi_\gamma; θ_p)$ were measured at four planes of gamma-rays registration. It allowed to restore sixteen even $A_{k \kappa}(θ_p)$ components of density matrix spin-tensor of the final nucleus $^{14}C(3^–)$. The obtained $A_{k \kappa}(θ_p)$ were used to determine other $^{14}C(3^–)$ orientation characteristics: the populations $P(θ_p)$ of sublevels with the M projection of the $3^-$ spin, orientation tensors $t_{k \kappa}(θ_p)$ and polarization tensors $T_{k \kappa} (2 \leq k\leq 6)$.
Experimental data were compared with theoretical ones, obtained within the neutron stripping mechanism by the coupled-channel method (code FRESCO [2], dotted curves in fig. 1a, b, c) and for the compound nucleus statistical mechanism (code CNCOR [3], dash-dot curves).
Our model analysis of $^{14}C(3^–)$ orientation characteristics has revealed that neutron stripping mechanism are dominant mechanisms of $^{13}C(d,p )^{14}C(3^–)$ reaction.
The problem of halo nuclei [1] in a detailed analysis of sizes and deformations in isotopic series reveals not abrupt behavior in the topology of nuclei, but a sequential continuous change in the structural nuclear parameters as they move away from the axis of the "Line of stability". This suggests the inevitable correlation of structural isotopic parameters with electromagnetic and purely nuclear [2].
In the this work, this phenomenon is traced by the example of isotopic series of Barium and Xenon, in which, as in the previous study [2], it was possible to find a correlation between the parameter β2 and half-life Т1/2 for oblate nuclei with signβ2<0 and anti-correlation for elongated nuclei signβ2>0. Using the found analytical expressions for the function β2(Т1/2) in these isotopic series, it is possible to semi-empirically approach the boundary of the bound states of nucleon systems both from the side of neutron-deficient nuclei and from the side of neutron-rich ones, which is an independent fundamental problem. These relations make it possible to calculate quadrupole deformation parameters β2 from the usually measured half-lives Т1/2 with high accuracy (from 5 to 10%), and through them the average radii of exotic nuclei <R>. Of particular interest is the possibility of extending this pattern to the region of superheavy nuclei. This method is a new way of assessing the Z-region, in which, probably, the maximum of the “Island of stability” is located.
In addition, when considering isotopic changes in the radii of nuclei in the present work, it can be seen that if the law of growth of radii, based on the growth of their masses <R>=r0A^(1/3) (or for isotopic series <R>=r0N^(1/3) is well observed in the direction of neutron excess, then this law is broken in the direction of neutron deficiency due to Coulomb repulsion of protons. And, as the mass number А decreases, it does not lead to a decrease in their radii, but, on the contrary, to their growth. This effect apparently allows for the first time to ascertain the experimental detection of void nuclei.
INTRANUCLEAR CASCADES EFFECTS ON THE COMPOSITION AND ENERGY OF (p,x)-NUCLEAR REACTION PRODUCTS
Novikov N.V., Chechenin N.G., Chuvilskaya T.V.,
Chumanov V. Ya., Shirokova A.A.
Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University,
Moscow, Russian Federation
E-mail: nvnovikov65@mail.ru
The relaxation of the nucleus in the pre-equilibrium phase, excited in reaction with protons of high energy, proceeds predominantly via an emission of several nucleons and α-particles. In addition to light nuclei with Z ≤ 2 and neutrons at the proton energies E0 > 140 MeV, γ quanta, leptons, and mesons there can also be emitted. The charge, mass, and energy distributions of heavy fragments formed in the collisions of protons with silicon and iron nucleus are studied using TALYS-1.9 [1], GEANT4 [2] and FLUKA [3] programs. The divergence between TALYS and GEANT4, FLUKA results above 300 MeV is analyzed and ascribed to the contribution of intranuclear cascades developed in the p+Si and p+Fe nuclear systems which is taken into account in GEANT4 and FLUKA, but not in TALYS. From the comparison, we deduce the essential role of intranuclear cascades in the compound p+Si and p+Fe nuclear systems at the pre-equilibrium phase of reaction at high colliding energies.
The method being successfully used for the synthesis of superheavy elements is that of complete fusion reactions, which are classified as cold fusion and hot fusion reactions. In the present work, we have studied the excitation functions (EFs) of ${}^{260}$Sg${}^{*}$, formed in fusion reaction ${}^{52}$Cr + ${}^{208}$Pb [4], based on Dynamical Cluster decay Model (DCM) [1]. For the nuclear interaction potentials, we use the Skyrme energy density functional (SEDF) based on semiclassical extended Thomas Fermi (ETF) approach under frozen density approximation. The Skyrme force used is the new GSkI force [3] for our calculation for cross section and comparison with the experimental data taken from [4]. Here, only the EFs for the production of ${}^{260}$Sg${}^{*}$ isotope via 2n decay channel from the ${}^{260}$Sg${}^{*}$ compound nucleus are studied at E*= 13 to 19 MeV for incoming channel, including quadrupole deformations $\beta_{2i}$ and cold-optimum" orientations $\theta_{i}$.The calculations are made within the DCM where the neck-length $\Delta$R is the only parameter representing the relative separation distance between two fragments and/or clusters $A_{i}$ (i=1,2) which assimilates the neck formation effects. Our calculations are shown in table.
Table:1 The “cold fusion” excitation function of 2n evaporation channels from ${}^{260}$Sg${}^{*}$ due to entrance channels ${}^{52}$Cr + ${}^{208}$Pb, calculated on the basis of DCM for a best fit of ∆R, at different E*= 13 to 19 MeV energies for GSkI Skyrme.
The calculations are made for best fit to each and every data point and clearly, irrespective of excitation energy, Skyrme Force GSKI included DCM reproduces data nicely.
References:
1. R. K. Gupta, in Lecture Notes in Physics,818, Vol. 1, Clusters in Nuclei, edited by C. Beck (Springer-Verlag, Berlin, Heidelberg, 2010), pp. 223-264.
2. Niyti, et el., Phys. Rev. C. 95, 034602 (2017).
3. C. M. Folden, et el., Phys. Rev. C. 79, 027602 (2009).
4. Aman Deep, et al. 1950079, (accepted) IJMPE (2019).
Sets of fission yields have an impact on different fields of interest. From a theoretical standpoint they are interesting for the understanding of matter, because they allow the description of the phenomena occurring in a nucleus undergoing large collective motion at low excitation energy and, hence, are influenced by nuclear shells that disappear at higher excitation energies. From a practical standpoint fission yields are of importance for the design of nuclear reactors and for waste management.
The purpose of work was definition of independent yields - number of atoms of a specific nuclide produced directly (not via radioactive decay of precursors) in fission reactions. Measured heavy fission products distributions on ionic charges for 239Pu(nth,f) reaction are used for estimation of isobar composition [1]. The basic difficulty consisted in correct transition from measured ionic charges to charges of heavy fragments at the moment of nuclear fission. For this transition we used the modified expression from [2]. Isobar yields for the measured heavy fission products of 239Pu (nth, f) reactions are defined and compared with theoretical data [3].
T-odd effects in fission of heavy nuclei have been extensively studied during more than a decade in order to study the dynamics of the process. A collaboration of Russian and European institutes discovered the effects in the ternary fission in a series of experiments performed at the ILL reactor (Grenoble) [1-3] and the effects were carefully measured for a number of fissioning nuclei. The analogous effects for gammas and neutrons in fission of 235U and 233U were also measured [3-6] after the observation of T-odd effects for ternary particles accompanying the reaction 235U(n,f) induced by cold polarized neutrons. All experiments up to now were performed with cold polarized neutrons, which suggests a mixture of several spin states of the compound nucleus, the relative contributions of which are not well known. The measurements of gamma and neutron asymmetries in an isolated resonance of uranium are important in order to get “clean” data. Therefore, our team continues to carry out a series of experiments by polarized neutrons with different energies. The present work describes a number of our team’s measurements that include the results of T-odd effects in the fission of uranium isotopes by polarized neutrons with different energies at the POLI facility and the MEPHISTO beamline of the FRM2 reactor in Garching.
Up to date analysis of velocity and isotope distributions of light fragments obtained in the projectile fragmentation reactions of 18O at 35 MeV/nucleon on 9Be and 181Ta targets measured at COMBAS fragment separator at the U400M Research Facility in JINR [1] are presented. The results of velocity spectra analytical parametrization and isotopic ratios are compared with the ones obtained in the experiments presented in the literature [2,3]. The discussion of the different mechanisms involved in these types of the reactions is given.
[1] A.G. Artukh et.al. Multi-nucleon transfers in reactions 18O(35MeV/nucleon)+181Ta(9Be), 2020, Pepan Letters - submitted
[2] X. H. Zhang et.al. Projectile fragmentation reactions of 40Ar at 57 MeV/nucleon, 2012, Phys. Rev. C 85,024621
[3] M. Mocko, M. B. Tsang et.al. Projectile fragmentation of 40Ca, 48Ca, 58Ni, and 64Ni at 140 MeV/nucleon, 2006, Phys. Rev. C 74, 054612
A new region of asymmetric nuclear fission zone of extremely neutron deficient sub-lead island has been emerged out in recent years from the discovery of unusual mass-asymmetry in 180Hg [1-4]. These extremely neutron-deficient exotic nuclei play an important role to understand the influence of microscopic effects near saddle point on the fission process [1]. The asymmetric nature of fission fragments of 180Hg examined in β-delayed fission of 180Tl at the excitation energy of 10.4 MeV is found to persist towards high excitation energies up to 85 MeV formed in the 36Ar+144Sm [2,3]. To test the relative presence of asymmetric distributions nearby fissioning nuclei 180Hg, 182Hg, and 178Pt formed via 36Ar+144Sm, 40Ca+142Nd, and 36Ar+142Nd, respectively [3,4], a comparative study has been carried out at similar excitation energies and angular momenta. The mass and total kinetic energy distribution of fission fragments of 180,182Hg was determined from the measured velocity and position information of coincident fission fragments using the double-arm time-of-flight spectrometer CORSET utilizing the U400 cyclotron at FLNR, JINR, Dubna. Fission fragment mass distributions of 182Hg, 180Hg, and 178Pt is shown in the figure at similar excitation energies and angular momenta. It is clearly evident from the figure that there are variations in the width of mass distributions at lower excitation energy that vanishes at higher excitation energy. However, significant variations at the central part of mass distributions indicate that the contribution of asymmetric distribution in 182Hg is relatively large in comparison to its nearby fissioning nuclei 182Hg/178Pt differing by only two neutrons/protons, respectively.
Highly-charged stable or radioactive ions can be stored and cooled in a heavy-ion storage ring offering unrivaled capabilities for precision studies for the atomic, nuclear structure, and astrophysics [1]. We have employed the unique feature of the Experimental Storage Ring (ESR) facility at GSI to address astrophysically relevant reactions. In 2009, as a proof-of-concept experiment, the cross section of 96Ru(p,γ) has been successfully investigated [2]. Later, in 2016 the study of the 124Xe(p,γ) reaction has been performed with decelerated fully-ionized 124Xe54+ ions [3]. Using a Double Sided Silicon Strip Detector (DSSSD), introduced directly into the Ultra High Vacuum environment of the storage ring, the 125Cs proton-capture reaction products have been successfully detected on the high energy tail of the Gamow-window for hot, explosive scenarios. Early this year, in March 2020, as the next step in our experiment campaign the first attempt was carried out to measure the proton-capture using a radioactive ion beam.
In this contribution, our precision (p,γ) reaction studies will be introduced highlighting the developments on the used measurement techniques. In addition, a novel approach will be expounded to increase the sensitivity of the identification for (p,γ) products by combining active ion scraping with offline energy selection on the detected ions.
References
[1] Bosch F et al 2013 Prog. Part. Nucl. Phys. 73 84
[2] Mei B et al 2015 Phys. Rev. C92 035803
[3] Glorius J et al 2019 Phys. Rev. Lett. 122 092701
One of the main attributes of reactor core design is finding the best distribution of the core controls and protection systems. Nuclear reactors have several distinctive types of control and protection elements, such as control rods, shimming rods and emergency rods. Each of these elements performs a separate task in a control procedure. The distribution of these elements in the core contributes to their worth and expense, therefore finding the best location and distribution of the control protection system (CPS) elements is very important from the viewpoint of nuclear reactor design and safety. The scope of this paper is to present the neutronic parameters such as effective multiplication factor (Keff), Neutron Spectrum and CPS worth calculation of research heavy water reactor using MCNPX code. In order to reduce the possible systematic errors due to inexact geometry, a very exact three-dimensional model of Reactor was developed. The MCNPX2.6 input file was prepared in such a way that a very quick setup of any desired core configuration with an adequate position of all Control and Protection Systems (CPS) is possible. Utilizing the appropriate material cross-sections in an MCNP calculation is essential to obtain reliable results. The MCNP neutron interaction tables used in this study are processed from ENDF/B-VII evaluated data file at room temperature. The thermal scattering treatment was used for light and heavy water, and polyethylene.
The obtained computational data showed that when all the emergency rods are fully inserted in the core, or when all the emergency channels are filled by light water, the negative imposed reactivity is more than the clean core excess reactivity (5% ΔK/K) plus 1%. Therefore, the emergency system satisfies the nuclear safety regulations.
In the work is investigated the effect of a burnable poison on the rate of reactivity drop in the PIK reactor. The core consists of six 6-sided fuel assemblies in the inner perimeter, six 4-sided fuel assemblies and six 6-sided fuel assemblies in the outer perimeter. The hexagonal fuel assembly contains 241 fuel elements, and the tetrahedral fuel assembly - 161. The fuel elements of the PIK reactor have a cruciform cross-section. The used fuel is $UO_2$ with the addition of Cu and 0.6% of Be. The mass of $^{235}U$ in one fuel element is 8.57 grams. There are 6 displacers or rods of a burnable poison in a hexagonal fuel assembly, and 14 or 2 rods of a displacer and 12 rods of a burnable poison in a tetrahedral one. Rods of a burnable poison have a form of half-cylinders in the clad of steel alloy EI-847. The material of the burnable poison is a powder of oxides $ZrO_2$ + 20%$Y_2O_3$ + 5.2% $Gd_2$$O_3$ mixture[1]. The main absorbing element are gadolinium isotopes $^{155}Gd$ (14.73%) and $^{157}Gd$ (15.68%), with cross sections equal to 60,900 × $10^{28}$ $m^2$ and 254,000 × $10^{28}$ $m^2$, respectively. The total gadolinium content in one rod is 0.7 grams. The fuel assembly cladding is made of zirconium alloy.
The time variation of the multiplication factor was calculated for two core design options. In the first case, only displacer rods made of E-125 zirconium alloy are used and in the second case, the rods of a burnable poison and two steel displacer rods made of 12Kh18N10T steel are used. The calculations were performed using the MCNP Version 6.1 program [2]. The calculation of the multiplication factor showed that the using of burnable poison reduces the multiplication factor at the beginning of operation cycle, but the initial reactivity is still too high to be compensated with the reactor control rods, as shown in the figure. To reduce the initial reactivity it was decided to use additional boric burnable absorber in zirconium alloy.
The bibliography list:
1.Computer model of the PIK reactor based on the MCNP. Calculations of neutron-physical parameters at the stage of physical reactor start-up. / K. A. Konoplev, A. S. Zakharov, A. S. Poltavsky, I. M. Kosolapov - Gatchina: Report, 2011.
2.MCNP USER’S MANUAL Code Version 6.2 / Edited by: Christopher J Werner ‒ Los Alamos National Security, LLC, 2017
The paper presents the development stage of an installation for fast neutron spectrometry using an EJ-276 plastic organic scintillator including the results and processing of measurements of mixed gamma-neutron spectra of an ING-07T pulsed neutron generator, calibration of the spectrometer, and unfolding of neutron spectra. Separation of signals from gamma and neutron radiation was carried out on a CAEN-DT5730 digitizer using the pulse shape discrimination (PSD) method. The obtained experimental results are compared with the results of mathematical modeling in the GEANT4.
The PSD spectra of the ING-07T pulsed neutron generator with and without a neutron moderator were measured, as well as the spectra of the spontaneous fission source Cf-252. As a result it was possible to successfully separate the mixed signal of the neutron generator into signals generated by gamma and neutron radiation with acceptable quality (parameter Figure of Merit (FoM) ~ 1.5 at a radiation detection threshold of 200 keV). At the same time, PSD separation with FoM> 1 is considered to be of high quality.
The spectrometer based on an organic scintillator was calibrated. Calibration in this case is an independent task due to the absence of full absorption peaks in the energy spectrum and is carried out along the Compton edges by using simulated spectra. In addition, it was shown that, due to the different light outputs from neutron and gamma radiation, calibration should be carried out separately for each type of radiation (in this case, according to the electrons and protons of the recoil). At the same time, neutron calibration was carried out based on our own experiment and published data on measuring the light output in an EJ-299 plastic scintillator (analogous to EJ-276) [1-3].
Moreover, the neutron energy spectra of a pulsed neutron generator and a spontaneous fission source Cf-252 were unfolded using least squares method and maximum entropy method (MAXED program). It is shown that results of unfolding are correct and, therefore, this technique will allow us to restore spectra from other types of neutron sources.
References:
[1] Mark A. Norsworthy et. al. Evaluation of neutron light output response functions in EJ-309 organic scintillators. Nuclear Instruments and Methods in Physics Research A 842 (2017) 20–27
[2] Chris C. Lawrence et.al. Neutron response characterization for an EJ299-33 plastic scintillation detector. Nuclear Instruments and Methods in Physics Research A759(2014) 16–22
[3] S. Nyibule et. al. Birks’ scaling of the particle light output functions for the EJ-299-33 plastic scintillator. Nuclear Instruments and Methods in Physics Research A 768 (2014) 141–145
The aim of the iDream project is a development of an industrial detector of the reactor antineutrinos for the reactor active zone monitoring. There is a description of the control methodology, a prototype design and a status of the project up to date.
LITHIUM-LOADED PLASTIC SCINTILLATORS FOR THERMAL NEUTRON DETECTION
Nemchenok I.B.1, 2, Kamnev I.I. 1, Shevchik E.A.1, Suslov I.A.1, 2
1Joint Institute for Nuclear Research, Dubna, Russia;
2Dubna State University, Dubna, Russia.
nemch@jinr.ru
This work presents the results of the optimization of the composition of lithium-loaded plastic scintillators (Li-PS) based on a copolymer of styrene and methacrylic acid. The light output, transparency and luminescence spectra were measured.
The composition of the Li-PS was optimized by measuring the light yield dependence on the concentrations of the primary (PPO) and secondary (POPOP) scintillation additives, as well as the secondary solvent (naphthalene). Lithium acetate was used as a lithium-containing additive.
As a result, the samples of lithium-loaded plastic scintillators with optimal concentrations were obtained: PPO – 4%, POPOP – 0.02%, naphthalene – 15%. The maximum concentration of lithium in the obtained samples was 0.3%.
Figure. The dependence of the light yield of scintillators based on a copolymer of styrene and methacrylic acid containing 4% PPO, 0.02% POPOP and 15% naphthalene on the concentration of lithium (relatively to the light yield of unloaded polystyrene based plastic scintillator).
The light yield of designed Li-PS practically does not depend on the metal fraction and is close to the half of the light yield of unloaded polystyrene based plastic scintillator.
Abstract. A new time-of-flight method for measuring the neutron lifetime $\tau_{\mathrm{n}}$ was proposed in [1] The time-of-flight method for measuring the neutron lifetime $\tau_{\mathrm{n}}$ is very sensitive to the background. It was found that the background should be less than $10^{-6}$. According to [2] , between the power pulses of the IBR-2 reactor, about $7 \%$ of the reactor power is allocated. Since the number of neutrons is proportional to the power of the reactor, the background from the delayed neutrons will also be $7 \%$ in 200 milliseconds. Measurements of the background of delayed neutrons were made and a complex dependence of the background on time was established. The influence of the background of the delayed neutron on the accuracy of measuring the neutron lifetime by the time-of-flight method is estimated.
References
1. V.L.Kuznetsov, E.V.Kuznetsova, P.V.Sedyshev. Measuring Neutron Lifetime on an $IBR-2$ Pulsed Neutron Source. Physics of Particles and Nuclei Letters, 2018 . Vol. $15,$ No. $6,$ pp. $678-684$
2. E.A.Bondarchenko, Yu.N.Pepelyshev, A.K.Popov. An experimental and model study of the dynamics of a pulsed batch reactor $IBR-2$. ECHAYA, $2004,$ v. $35,$ issue $4,$ pp. 927 983
An increase in the intensity of pulsed neutron sources leads to an unprecedentedly large pulsed neutron flux density up to $10^{11} \mathrm{n} / \mathrm{s} / \mathrm{cm}^{2}$ and, as a result, to the impossibility of using data acquisition systems operating in counting mode. On the other hand, in the study of small P-odd effects in stationary reactors, the integral method is often used. This article presents the results of measuring TOF spectra by the integral method.
New approach to solve a wide range of problems in various nuclear materials processing is discussed. One of them – irradiated reactor graphite decontamination with inert gas (argon) plasma sputtering and thermo-treatment with interdisciplinary synthesis of plasma physics, materials science and reactor physics. At present time wide search of effective technology to deactivate reactor graphite is very acute due to the large volumes of accumulated irradiated
graphite in the world (about 100 thousand tons) and the challenging problem of uranium-graphite reactors decommissioning period. Proposed high pressure short discharge technology has advantage compared with traditional radiochemistry in versatility (work with any kind of radionuclides, since ion etching process allows ones to sputter any atoms) and in the absence of the additional secondary radioactive wastes (as a buffer media is inert gas forming no chemical
compounds with radionuclides). It is known [1] that one of the possible contamination mechanisms of graphite masonry surfaces is the neutron activation of nitrogen atoms from the cooling gas mixture, as well as the process of intercalation of nitrogen migrating inside graphene-graphene layers of graphite.
This leads to the fact that the RBMK graphite masonry acquires significant activity due to the 14C isotope localized on and inside of the surface layers of micron depth. We experimentally studied sorption capacity of the surface for some fresh (before irradiation) reactor graphite samples and obtained that the 14C isotopes arising from nitrogen neutron activation may be localized under the
graphite surface of the 30 nm thickness. It is very suitable for plasma etching and provides problems for the other competitive technologies creating large volume of secondary radioactive wastes. Our estimates of operating parameters for the irradiated reactor graphite deactivation in an inert gas plasma were made for discharge current (0.001 - 1 A / cm2), voltage (300-1000V), inert gas pressure (0.01-1 atm.), gap between the treated graphite surface and the anode collector
(1-5mm). The reactor graphite temperature under treatment was in the range of 600-1800K [2], integrity of the treated graphite blocks remains and they are ready for a final burial, in comparison with competitive approaches.
Also proposed plasma technology is applicable for a fast deactivation of the internal of the nuclear power plants constructions during reload or repair periods, instead of radiochemical methods. Described plasma treatment provides removal and transfer of the surface contaminating radionuclides in highly concentrated form with the opportunity to extract selectively useful radioisotopes via proposed spatial differentiation of the sputtered atoms
condensation according to their individual evaporation temperatures.
Additionally, some modification of our technology can be used for a new scheme of spent nuclear fuel reprocessing with uranium deoxidation-oxidation reactions and fission fragments removal in plasma gas mixture with the following fuel sedimentation, adapted for the perspective new nuclear energetics and closed circulating fuel cycle. Technology is patented in collaboration of Intro-Micro LLC, Concern Rosenergoatom JSC and Rosatom [3] and is suitable for Fukushima NPPs accident dismantling efforts.
[1] Dunzik-Gougar M.L., Smith T.E. Removal of carbon-14 from irradiated graphite // Journal of Nuclear Materials / -2014 -V. 451 –P. 328–335
[2] A.S.Petrovskaya, A.Yu.Kladkov, S.V.Surov, A.B.Tsyganov «New Thermo-Plasma Technology for Selective 14C Isotope Extraction from Irradiated Reactor Graphite» AIP Conference Proceedings 2179, 020020 (2019)
[3] A.S.Petrovskaya, A.B.Tsyganov, M.R.Stakhiv "Method for deactivating a structural element of a nuclear reactor" Patent RU №2711292, International patent application PCT/RU2019/000816 (14.11.2019).
One of the promising type of scintillation detector for neutron registration and spectroscopy is Cs26LiYCl6:Ce. The work presents study of characteristics of this detector. Optimization of digital algorithms for neutron/gamma-separation was performed. Pulse shape discrimination quality of charge integration and correlation analysis was investigated. Also tuning of pulse start time measuring was carried out. Time resolution for signals obtained from registration neutrons and gamma-rays was compared.
Tyutyunnikov S.I. $^{1},$ Yuldashev B.S.$^{1},$ Kryachko I.A.${ }^{1},$ Rasulova F.A. $^{1},$ Stegailov $\mathrm{V}. \mathrm{I.}^{1},$ Tran $\mathrm{T.N.}^{1,2}$, Perevoshikov L.L., Guseva S.V. $^{1},$ Balandin A.S.
$^1$ - Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow region, Russia, 141980
$^2$ - Institute of Physics, Vietnam Academy of Science and Technology, Hanoi, Vietnam
e-mail: stegajlov2013@yandex.ru
The studies were carried out on proton beam with energy of 660 MeV, which generates a neutron field from “QUINTA”-setup [1,2].
The (n, γ) and fission reactions in the targets of ${}^{237}$Np and ${}^{241}$Am irradiated by neutron field were studied.
The obtained results were compared with the EXFOR experimental base and interpreted using the GEANT4 and FLUKA programs [3].
We extended our calculations of the recent research work for two flavor magnetized PNJL model cooperating non zero chemical potential and thermal mass in the potential as in the Lagrangian. We calculate the equation of state of PNJL model and its thermodynamic properties. We Show the results of the phase transition temperature obtain to a lower value in comparison to earlier value of phase transition, the result is much conformation with the lattice data. The result shows that the thermodynamic behavior of lattice data are well agreed with the prediction of the model field theories.
References:
Y. Nambu, G. J Lasinio, Phys. Rev D 122, 345 (1996).
C. Ratti et al, Phys. Rev D 73, 014019 (2006).
Models with extended Higgs boson sectors are of prime importance for
investigating the mechanism of electroweak symmetry breaking for Higgs decays
into four fermions and for Higgs-production in association with a vector bosons [1]. In the framework of the Two-Higgs-Doublet Model [2] using two scenarios obtained from the experimental measurements we presented next-to-leading-order results on the four-fermion decays of light CP-even Higgs boson, $h \rightarrow 4f$ [3]. With the help of Monte Carlo program Prophecy 4f 3.0 [4], we calculated the values $\Gamma= \Gamma_{EW} /\left(\Gamma_{EW}+\Gamma_{SM}\right)$ and $\Gamma= \Gamma_{EW+QCD} /\left(\Gamma_{EW+QCD}+\Gamma_{SM}\right)$ for Higgs boson decay channels $ H \rightarrow \nu_{\mu} \overline{\mu} e \overline{\nu_e}$, $\mu \overline{\mu} e \overline{e}$, $e \overline{e} e \overline{e}$. We didn't find significant difference when accounting QCD corrections to EW processes in the decay modes of Higgs boson.
Using computer programs Pythia 8.2 [5] and FeynHiggs [6] we calculated the following values: $\sigma(VBH)BR(H\rightarrow ZZ)$ and $\sigma(VBF)BR(H \rightarrow WW)$ for VBF production processes, $\sigma(ggH)BR(H \rightarrow WW)$ and $\sigma(ggH)BR(H \rightarrow ZZ)$ for gluon fusion production process at 13
and 14 TeV and found good agreement with experimental data [7].
References:
1. CMS Collaboration. Measurements of properties of the Higgs boson decaying into four leptons in pp collisions at $\sqrt{s}=13$\ TeV // CMS-PAS-HIG-16-041 (2017).
2. A.Denner, S.Dittmaier, J.-N.Lang. Renormalization of mixing angles // JHEP 2018,11,104, arXiv:1808.03466 [hep-ph].
3. D. de Florian et al. Handbook of LHC Higgs Cross Sections: 4. Deciphering the Nature of the Higgs Sector // CERN Report 2017-002 (2016), [arXiv:1610.07922].
4. A.Denner, S.Dittmaier, A.Muck. PROPHECY4F 3.0: A Monte Carlo program for Higgs-boson decays into four-fermion final states in and beyond the Standard Model // FR-PHENO-2019-018, TTK-19-51, arXiv:1912.02010 [hep-ph].
5. T.Sjostrand. An Introduction to PYTHIA 8.2 //
Comput.Phys.Commun. 2015, 191, 159-177, arXiv:1410.3012 [hep-ph].
6. S.Heinemeyer, W.Hollik, G.Weiglein. FeynHiggs: a program for the calculation of the masses of the neutral CP-even Higgs bosons in the MSSM // Comput.Phys.Commun. 2000, 124, 76-89.
7. ATLAS Collaboration. Measurements of gluon-gluon fusion and vector-boson fusion Higgs boson production cross-sections in the
$H\to WW^*\to e\nu\mu\nu$ decay channel in pp collisions at $\sqrt{s}=13$\ TeV with the ATLAS detector // Phys. Lett. 2019, B 789, 508.
The interrelation between the deconfinement temperature of hadron medium
and parameters of radial Regge trajectories within the bottom-up holographic
models for QCD is scrutinized. We show that the lattice data on the deconfine-
ment temperature can yield a powerful restriction on the spectrum of excited
mesons and glueballs within the framework of holographic approach.
At present, experiments devoted to studying collisions of hadrons and nuclei at high energy are being performed at various facilities, including the LHC and SPS (CERN) and RHIC (BNL). Due to the peculiarities of the strong interaction, constructing a collision model from the first principles of the QCD theory is a rather difficult task. Therefore, various empirical models are developed based on the available experimental data. The basic model for describing interactions involving hadrons and nuclei is the Glauber model [1-2]. For the more detailed description of nuclear interaction features, this model is increasingly being used at the parton level [3-5], however, usually, pp-interaction is given insufficient attention. Before the transition to the nucleus-nucleus collisions, one should ensure that the major features of the pp interaction are adequately described.
In this regard, the work is devoted to a systematic study of pp collisions in a wide energy range at the parton level.
The Glauber Monte Carlo model was developed and implemented for a detailed description of pp collisions at the parton level. Various types of spatial parton distributions in the proton are considered. It is shown that, within the framework of this model, such quantities as the total, elastic, and inelastic cross sections, the slope of the diffraction cone in the energy range from SPS to LHC are satisfactorily described, while the best agreement with experiment is obtained for the exponential form of the spatial parton distribution.
The self-consistency of the model is checked regarding the transition to a moving reference frame. An explicit form of the dependence of the number of initial partons on the beam energy is obtained, which ensures the exact Lorentz invariance of the cross sections and the slope of the diffraction cone, and the values of its parameters are determined. The behavior of proton-proton cross sections in the high-energy limit is analyzed. The developed approach can be applied not only to pp interaction but also can serve as the basis for more advanced models of both pp and AA collisions.
References
The hadronization of the deconfinement matter is considered based on the concept the quark-hadron duality. Under such an approach the hadron rate is shown to be the convolutions of the multiple particle Green's function of quarks in the Kadanoff-Baym-Keldysh formalism with the probability to create the quasi-hadron bound quark-antiquarks states in the deconfinement matter. This probability depends strongly on the color correlation in the deconfinement matter. When the probability is governed by the first order phase transition, the rapidity distribution of two- and tetra-quark hadrons is explicitly calculated in the longitudinal dominance approximation. The derived rapidity distribution is compared with experimental data.
The scalar quark condensate $\kappa(\rho)=\langle M|\sum_{i}\bar q_i q_i|M\rangle$ in nuclear matter can be presented as $\kappa(\rho) =\kappa(0) + \kappa_N\rho+S(\rho)$ with $\langle M|$ the ground state of the matter while $q$ are the operators of the light quarks $u$ and $d$. Here $\rho$ is the density of the matters, $\kappa(0)$ is the vacuum value of the condensate. In the second term on the right hand side the matrix element $\kappa_N$ is $\kappa_N=\langle N|\sum_{i}\bar q_i q_i|N\rangle$ with $\langle N|$ standing for the free nucleon at rest. This matrix element can be expressed in terms of the nucleon sigma term $\sigma_N$ related to observables. The various experiments provide the values between 40 MeV and 65 MeV for $\sigma_N$. The first two terms in definition of $\kappa(\rho)$ compose the gas approximation.
The contribution $S(\rho)$ describes the change of $\kappa(\rho)$ caused by the nucleon interactions. It was demonstrated that $S(\rho)$ is due mostly to the pion cloud created by interacting nucleons (see [1] for references). In the latter calculations $S(\rho)$ was obtained employing the nonrelativistic approximation for nucleons of the matter (curve $1$ in Fig.1). The latest results obtained in framework of chiral perturbation theory [2] are shown by the curve $2$.
In the present report the matter is viewed as a relativistic system of nucleons. In the first step we neglect their interactions. We find that the quark condensate can be presented as $\kappa(\rho)=\kappa(0)+\kappa_N \rho F(\rho,m^*(\rho))$ with $F(\rho, m^*(\rho)) =2/(\pi^2\rho)\int^{p_F}_0\,dp\,p^2\,m^*/\sqrt{m^{*2}+p^2}$. Here $p_F$ is the Fermi momentum, $m^*$ is the nucleon Dirac effective mass. Note that the same function $F(\rho,m^*(\rho))$ connects the vector and scalar densities in the Walecka model.
The effective mass $m^*$ can be calculated in a hadron model. In the version of QCD sum rules presented in [3] the right hand side of the scalar channel equation contains the effective mass $m^*(\rho)$ while the left hand side contains the scalar condensate $\kappa(\rho, m^*(\rho))$. Thus we come to self-consistent equation for $m^*(\rho)$ which was solved in [3]. Here we employ these results for calculation of $\kappa(\rho)$ (curve $3$ in Fig.1). One can see that inclusion of the relativistic dynamics of nucleons is as important as that of nucleon interactions.
References:
[1] E.G.Drukarev,M.G.Ryskin,V.A.Sadovnikova, Phys.Atom.Nuclei,v.75,p.334(2012).
[2] S.Goda and D.Jido, Phys. Rev., v.C88,065204(2013).
[3] E.G.Drukarev,M.G.Ryskin,V.A.Sadovnikova,Eur.Phys.J.,v.A55,p.34(2019).
In many cases, interactions of nuclei are considered as collisions of A1 and A2 nucleons if it is possible to neglect the binding energy of the nucleus. However for very high kinetic energy of colliding nuclei there is a possibility of collective interaction of nucleons with production of quark-gluon matter blobs. As it was shown earlier, in this case a large orbital momentum appears. In that paper, calculations were made for equal nuclei. Here we generalize this approach and calculate orbital momentum for various ratios of radii of interacting nuclei.
In [1], in the framework of a general approach to the covariant description of
the structure of half-integer spin nuclei, analytical expressions were found for
the multipole expansion of the structure functions, entering into the
differential cross section for elastic scattering of longitudinally polarized
leptons
$
\frac{{d\sigma }}{{d\Omega }} = {\sigma _{Mott}}\left\{ {{W_1} +
2t{g^2}\frac{\theta }{2}{W_2} - \zeta \tau \left[ {\frac{M}{E} + \left( {1 +
\frac{M}{E}} \right)t{g^2}\frac{\theta }{2}} \right]{W_4}} \right\}.
$
In the effective current approximation, valid for high energies $E > > {m_l}$
of the scattered lepton, structure functions ${W_k}$ depend upon $\tau = -
{{{q^2}} \mathord{\left/
{\vphantom {{{q^2}} {4{M^2}}}} \right.
} {4{M^2}}}$, lepton helicity $\zeta $, and
electromagnetic and weak nucleus form factors, and lepton electroweak constants.
In this work using Rarita-Schwinger formalism to describe [2] nuclei with
half-integer spin $J \le 7/2$, we construct explicit expressions for covariant
electromagnetic and weak vertex functions $\Gamma _{em,\;weak}^{\mu {{\left(
\alpha \right)}_j}{{\left( \beta \right)}_j}}\;\left( {j = J - 1/2} \right)$,
as well as for the density matrix ${\Lambda _{{{\left( \alpha
\right)}_j}{{\left( \beta \right)}_j}}}$ of an unpolarized nucleus state. Then,
using multipole expansion technique in the Breit zero energy transfer system, we
consider traditional multipole form factors -- vector ${F_{Cl}}(\tau )\;\left( {l
= 0,2,\;...\;2J - 1} \right)$ and ${F_{Ml}}(\tau )\;\left( {l = 1,\;3,\;...\;2J}
\right)$, as well as axial ${F_{5El}}(\tau )$ and ${F_{5Ll}}(\tau )\;\left( {l =
1,\;3,\;...\;2J} \right)$ -- and get expressions for them through the covariant
form factors of the vertex functions $F_E^{(n)}(\tau ),\;F_M^{(n)}(\tau
),\;G_1^{(n)}(\tau )$ and $g_E^{(n)}(\tau ),\;g_M^{(n)}(\tau ),\;g_A^{(n)}(\tau )$.
Then we obtain and discuss expressions for the right-left asymmetry ${A_{RL}}$,
as well as the spin correlations of transversely polarized incident and scattered
leptons. We show, that elastic scattering is helicity conserving due to smallness
of the lepton mass, and right-left asymmetry contains contribution from anapole
moment of the target, whereas transverse correlations arise only with
simultaneous polarization of incident and scattered leptons.
The theoretical consideration of the $NN{\bar K}$ quasi-bound system is based on the isotopic-spin formalism in which mesons ${\bar K}^0$ and $K^-$ are two isospin states of the $\bar K$ particle with the isospin of $\frac12$. Nucleon is also considered as isospin $\frac12$ particle having two states (proton and neutron) with the different projections of the isospin. According to the isospin formalism, the isospins in the $NN{\bar K}$ system are summed as isospins of three identical particles. And along with this, in the $NN{\bar K}(s_{NN}=0)$ system, the particle channels $ppK^-$ and $pn{\bar K}^0$ are defined in literature due to the possible particle transition $n{\bar K}^0\to pK^-$. Taking into account this assumption, the system can be found as $ppK^-$ or $pn{\bar K}^0$ at the same time. The question is how these particle channels can be described within the isospin formalism.
In the presented work, the kaonic system $NN{\bar K}(s_{NN}=0)$ is studied based on the configuration space Faddeev equations. We considered two models associated with isospin "natural" basis and isospin "charge" basis. We show that the "particle representation" [1-3] for $NN{\bar K}(s_{NN}=0)$ system motivated by the "charge" basis does not describe the system in terms of coupled particle channels $ppK^-/pn{\bar K}^0$ [4]. The particle configurations of the $NN{\bar K}(s_{NN}=0)$ system may be classified by the masses and pair potentials (in particular, presence or absence of the Coulomb interaction). The $NN{\bar K}(s_{NN}=0)$ system is represented by four configurations: $ppK^-$, $npK^-$, $np{\bar K}^0$, $nn{\bar K}^0$. The results of the calculations including the kaon mass difference, the charge dependence of nucleon-nucleon interaction [5] and the Coulomb force for these particle configurations will be presented.
This work is supported by the National Science Foundation grant HRD-1345219 and NASA grant NNX09AV07A.
The spectroscopy of charmonium-like mesons with masses above the 2_mD open charm threshold has been full of surprises and remains poorly understood [1]. The currently most compelling theoretical descriptions of the mysterious XYZ mesons attribute them to hybrid structure with a tightly bound cc\bar diquark [2] or cq(cq)\bar tetraquark core [3 - 5] that strongly couples to S-wave DD\bar molecular like structures. In this picture, the production of a XYZ states in high energy hadron collisions and its decays into light hadron plus charmonum final states proceed via the core component of the meson, while decays to pairs of open-charmed mesons proceed via the DD\bar component.
These ideas have been applied with some success to the XYZ states [2], where a detailed calculation finds a cc\bar core component that is only above 5% of the time with the DD\bar component (mostly D0D0\bar) accounting for the rest. In this picture these states are compose of three rather disparate components: a small charmonium-like cc\bar core with r_rms < 1 fm, a larger D+D- component with r_rms = ħ/(2µ+B+)^1/2 ≈ 1.5 fm and a dominant component D0D0 with a huge, r_rms = ħ/(2µ0B0)^1/2 > 9 fm spatial extent. Here µ+(µ0) and B+(B0) denote the reduced mass for the D+D- (D0D0\bar) system and the relevant binding energy |m_D + m_D - M_X(3872)| (B+ = 8.2 MeV, B0 < 0.3 MeV). The different amplitudes and spatial distributions of the D+D- and D0D0 components ensure that the X(3872) is not an isospin eigenstate. Instead it is mostly I = 0, but has a significant (~ 25 %) I = 1 component.
In the hybrid scheme, XYZ mesons are produced in high energy proton-nuclei collisions via its compact (r_rms < 1 fm) charmonium-like structure and this rapidity mixes in a time (t ~ ħ/δM) into a huge and fragile, mostly D0D0, molecular-like structure. δM is the difference between the XYZ meson mass and that of the nearest cc\bar mass pole core state, which we take to be that of the χc1(2P) pure charmonium state which is expected to lie about 20 ~ 30 MeV above M_X(3872) [6, 7]. In this case, the mixing time, cτ_mix 5 ~ 10 fm, is much shorter than the lifetime of X(3872) which is cτ_X(3872) > 150 fm [8].
The experiments with proton-proton and proton-nuclei collisions with √S_pN up to 26 Gev and luminosity up to 10^32 cm^-2s^-1 planned at NICA may be well suited to test this picture for the X(3872) and other XYZ mesons. In near threshold production experiments in the √S_pN ≈ 8 GeV energy range, XYZ mesons can be produced with typical kinetic energies of a few hundred MeV (i.e. with γβ ≈ 0.3). In the case of X(3872), its decay length will be greater than 50 fm while the distance scale for the cc\bar → D0D*0 transition would be 2 ~ 3 fm. Since the survival probability of an r_rms ~ 9 fm “molecular” inside nuclear matter should be very small, XYZ meson production on a nuclear target with r_rms ~ 5 fm or more (A ~ 60 or larger) should be strongly quenched. Thus, if the hybrid picture is correct, the atomic number de-pendence of XYZ production at fixed √S_pN should have a dramatically different behavior than that of the ψ', which is long lived compact charmonium state.
The current experimental status of XYZ mesons together with hidden charm tetraquark can-didates and present simulations what we might expect from A-dependence of XYZ mesons in proton-proton and proton-nuclei collisions are summarized.
References
[1] S. Olsen, Front. Phys. 10 101401 (2015)
[2] S. Takeuchi, K. Shimizu, M. Takizawa, Progr. Theor. Exp. Phys. 2015, 079203 (2015)
[3] A. Esposito, A. Pilloni, A.D. Poloza, arXiv:1603.07667[hep-ph]
[4] M.Y.Barabanov, A.S.Vodopyanov, S.L.Olsen, A.I.Zinchenko, Phys. Atom. Nuc. 79, 1, 126 (2016)
[5] M.Yu. Barabanov, A.S. Vodopyanov, S.L. Olsen, Phys. Scripta 166 014019 (2015)
[6] N. Isgur, Phys. Rev. D 32, 189 (1985)
[7] K. Olive et al. (PDG), Chin. Phys. C 38, 090001 (2014)
[8] The width of X(3872) is experimentally constrained to be Г X(3872) < 1.2 (90% CL) in S.-K. Choi et al (Belle Collaboration), Phys. Rev. D 84, 052004 (2011)
Over the last decades, our knowledge on Neutron Stars (NS) has been greatly advanced: NS with large masses were discovered, radii of a number of NS were measured, and a gravitational signal from the merger of two NS was observed. These data establish significant restrictions on the equation of state of the NS matter and pose new problems for the theory of nuclear matter [1,2].
Many authors have been suggested the interplay between the properties of effective nucleon interactions used to calculate the equation of state and characteristics of NS. In this work, an attempt is made to put the study of such interplay on a quantitative footing. We analyze a large number of sets of parameters of the Skyrme nucleon-nucleon potential [3] and of the Lagrangian of the relativistic mean field theory [4] and calculate the coefficients of correlation between the saturation quantities of the nuclear matter and the NS properties.
The calculation indicates a strong correlation between the derivative of the symmetry energy and other quantities, which describe the nuclear matter energy dependence on the isospin asymmetry, on the one hand, and the radius and central density of NS with a mass of 1.4MSun, on the other hand. The significance of nuclear symmetry effects for NS structure is obvious and has been numerously discussed. However, we did not find a meaningful correlation between the symmetry properties and the maximum NS mass. There is also almost no correlation between the characteristics of NS and the incompressibility of the infinite symmetric nuclear matter. This shows that the stiffness of the equation of state of the NS matter is not directly related to the incompressibility. The correlations in the non-relativistic the Skyrme approach and the relativistic mean field theory are similar, therefore, we observe real (non-model) relationships between physical quantities.
The existence of an axion (a hypothetical pseudoscalar boson) was originally considered as a consequence of sponatneous breaking of newly introduced chiral symmetry, which was suggested in 1977 by R. Peccei and H. Quinn in attempt to solve the strong CP problem. The interactions of axion with ordinary matter are described via the effective coupling constants that are inversely proportional to the symmetry breaking scale $f_A$. The experimental searches for axion have been attempted ever since its original introduction, although none had yielded positive results so far.
After exclusion of "standard" axion (that assumed $f_A \approx 250$ GeV, comparable to the electro-weak scale), the theoretical model were modified so that $f_A$ value was allowed to become arbitrary large, therefore supressing the axion couplings and reducing its mass. This led to the appearance of light and weakly interacting "invisible" axion, which naturally became the viable dark matter candidate, further stimulating the motivation for its experimental discovery.
Axions should be intensely produced inside stellar cores and significant portion of axion experiments is targeted towards the detection of solar axions. Due to the axion-nucleon coupling axions can undergo resonant absorption in nuclear transitions of M1-type. A series of experiments were performed at Petersburg Nuclear Physics Institute searching for the resonant absorption of solar axions by several target nuclei ($^7$Li [1], $^{57}$Fe [2], $^{169}$Tm [3], $^{83}$Kr [4]).
A new technique, developed in collaboration with Max Planck Institute for Physics (Munich) and Kurchatov Institute (Moscow), allows for a significant increase in experiment sensitivity by employing the cryogenic bolometer detector based on the Tm-containing crystal [5]. This new approach scalable and can be potentially used for installation with a kg scale target.
The response function of the recoil nuclei in the detectors designed to detect neutrinos or dark matter particles can be determined only by using a neutron source with known energy spectrum. Therefore, the development and creation of a calibration neutron source is an important task for a number of current and future nuclear and astrophysical experiments [1, 2]. The neutron source has to be combined with a semiconductor detector that detects the moment of neutron appearance.
Silicon semiconductor detectors are widely used in various nuclear physics experiments and possess perfect operating parameters, such as thin window layer, sufficient temporal and good energy resolutions. However, their performance could be considerably limited by the radiation defects formed during the operation process. Since in the suggested experiments [1, 2] semiconductor detectors should operate under intense level of α-particles and fission fragments irradiation, which inevitably accompany the process of spontaneous fission of the nucleus, studies of the radiation hardness of Si detectors are of a significant importance for the successful implementations of the suggested nuclear physics experiments.
This work is devoted to the investigations of Si detectors parameters degradation during long-termed irradiation by α-particles. For these investigations an experimental setup for simultaneous measurement of α-particles spectrum and determination of the operational indications of the detector degradation (decrease of energy resolution and signal-to-noise ratio, growth of the reverse current, etc.) was developed by our group. Two types of Si detectors were under investigations - silicon-lithium Si (Li) p-i-n detectors and silicon surface barrier detectors. As a result of the measurements, the maximal permissible radiation doses for the correct operation of the detectors of both types and the correlation between the received radiation dose and the spectroscopic characteristics of the detectors were determined. Additional set of experiments was aimed to study the type and concentration of the radiation defects formed under irradiation. Detailed discussion of the obtained experimental results will be presented at the Conference.
The reported study was funded by RFBR, project number 20-02-00571.
[1] D. Akimov, J.B. Albert, P. An, C. Awe, P.S. Barbeau, B. Becker, V. Belov, A. Brown, A. Bolozdynya, B. Cabrera-Palmer, M. Cervantes, J.I. Collar, R.J. Cooper, R.L. Cooper, C. Cuesta, et al., Coherent Coll., Observation of coherent elastic neutrino-nucleus scattering, Science, Vol. 357, Issue 6356, pp. 1123-1126 (2017)
[2] C. E. Aalseth, F. Acerbi, P. Agnes, I. F. M. Albuquerque, T. Alexander, A. Alici, A. K. Alton, P. Antonioli, S. Arcelli, R. Ardito, I. J. Arnquist, D. M. Asner, M. Ave, H. O. Back, A. I. Barrado Olmedo et al., DarkSide Coll., DarkSide-20k: A 20 tonne two-phase LAr TPC for direct dark matter detection at LNGS, Eur. Phys. J. Plus 133, 131 (2018)
ELECTRON PARAMAGNETIC DATING OF FOSSIL TOOTH FOUND AT THE AGHSTAFA DISTRICT IN AZERBAIJAN
Mammadov S.G., Ahadova A.S.
Institute of Radiation Problems, Azerbaijan National Academy of Sciences, Baku Az1143, Azerbaijan
aybaniz.ahadova@mail.ru
At present, the study of an archaeological site without the associated radioisotope research methods is an anachronism. As many geoarchaeologists rightly point out, the cultural layer cannot be fully studied only by excavating and collecting artifacts; this requires the application of methods of natural sciences.
Electron paramagnetic resonance (EPR) analysis is one of the alternative methods on dating of ancient artifacts and based on the fact that natural ionizing irradiation produces paramagnetic centers in tooth enamel with the long mean life. Those centers are stable at the temperatures below 100 ºC and might be considered as a measure of the total irradiation dose to which a particular sample has been exposed. In this work the EPR method has been applied to determine the age of animal tooth enamel found in Aghstafa archeological site in Azerbaijan. Method based on the fact that the intensity of the EPR signal increases linearly with the additional laboratory irradiation. The enamel was initially removed from teeth using a dental drill and water cooling. The 2 mm mean thickness enamel was then placed in a 30% NaOH solution for one day to disinfect it and separate any remaining dentine. A dental drill was used to strip around 50±5 µm from inside and outside of the enamel surface to ensure that alpha radiation had no effect. In total 0.6 g enamel was collected and it was air-dried at room temperature for three days. ESR signal for the sample was measured with a Bruker EMXplus (X-band) spectrometer. Fig. 1 shows the dose dependence spectra for the enamel sample from the tooth found Aghstafa district of Azerbaijan. The archaeological dose obtained by the extrapolation back to zero ordinate was 9.73±0.47 Gy. In order to estimate the natural dose rate soil samples were collected from the site and U, Th, and K content analysis by gamma spectrometry Canberra GR4520. ROSY program was employed to calculate the age of tooth enamel. The age of the tooth found in Aghstafa archeological site was estimated as 8432+/-416 BP.
$^1$ NRC “Kurchatov institute” – ITEP, Moscow, 117218, Russia;
$^2$ National Research Center “Kurchatov institute”, Moscow, 123182, Russia.
First observation of neutron star merger and registration of heavy elements presence in this process [1] confirmed our understanding that main scenario for the r-process is connected with the ejecta during neutron star merger (NSM) at the end of close binary system evolution rather than with the supernova explosion [2].
A number of NSM model were created [3] since 1999 year and with their help the main conditions of the r-process in jets were researched. Neutron stars in close binaries is approaching each other because the system lost angular momentum due to gravitation wave emission. Further evolution of their mutual approaching and merger depend on masses of binary components. In case when masses are close to each other and when the mass of every component is close to solar mass (it usually is called as “standard” neutron star mass), then scenario of neutron stars merger is realized.
In present report we will discuss the binary of neutron stars when neutron stars have significantly different masses, $m_1$ > $m_2$ [4]. In such a binaries the matter of the component with smaller mass starts to flow from low-mass companion to higher-mass one $m_1$. When the mass of low-mass neutron star have reached the minimum mass value ~0.1$M_⊙$, the low-mass companion lost its hydrodynamical stability and blows up [5].
On the results of first calculations of low-mass companion of close neutron stars system, for the ejecta with different chemical composition the nucleosynthesis calculations of heavy elements were done and theoretical abundances of heavy elements are in a good agreement with our knowledge of solar system matter.
The work was under under financial support of Russian Fond of Basic Research (project №. 18-29-21019 мк).
Machine Learning (ML) have been widely applied in the High Energy Physics (HEP) to help physical community to solve complex problem in classification and analysis. Here we describe application of ML to solve the problem of classification background and signal events in DEAP-3600 experiment (SNOLAB, Canada) that constructed to search WIMP particles. We apply Boosted Decision Trees (BDT) method of ML, which upgraded by using Extra Trees and eXtra Gradient boosting method (XGBoost).
In this work, we consider a beyond the Standard Model (SM) framework, based on the non-abelian discrete group $\Delta(27)$ to explain the observed non-zero reactor mixing angle $\theta_{13}$. The deviation from the tri-bimaximal (TBM) neutrino mixing pattern, in the context of the type-I seesaw is realized by including new particles to the SM particle content, which thus provides non-zero $\theta_{13}$, consistent with the recent experimental results. The non-zero neutrino masses can be understood via type-I seesaw mechanism by introducing three right-handed neutrinos, which transform as triplets and a $SU(2)_L$ scalar singlet under $\Delta(27)$ symmetry. Similarly, to accommodate the charged lepton mass, $SU(2)_L$ scalar doublets transforming as singlets under $\Delta(27)$ symmetry are also included. We demonstrate that, the model successfully explains all the neutrino oscillation parameters such as the atmospheric and solar mass squared differences, all the mixing angles and the CP-violating phase $\delta_{CP}$, as well as the cosmological bound on the sum of active neutrino masses $(\sum_{i}m_i)$. In addition, it also explains the baryon asymmetry of the Universe through Leptogenesis. The non-zero lepton asymmetry is generated through the decay of the right handed neutrinos, involving the neutrino Yukuwa couplings.
Precise knowledge of forbidden transition beta-spectra plays a significant role in both nuclear and particle physics.
In this work we present a precision measurement of the beta-spectrum shape for $^{210}$Bi (historically RaE) performed with spectrometers based on semiconductor Si(Li) detectors. This first forbidden non-unique transition has the transition form-factor strongly deviated from unity and knowledge of its spectrum would play an important role in low-background physics in presence of $^{210}$Pb background. The studies were performed with spectrometers in target-detector and 4-$\pi$ geometries. The measured transition form-factor could be approximated as $H(W) = 1 + (-0.433 \pm 0.002) W + (0.0510 \pm 0.0004) W^2 $ and $H(W) = 1 + (-0.433 \pm 0.002) W + (0.0510 \pm 0.0004) W^2 $ for the target-detector and 4-$\pi$ spectrometer respectively that is in good agreement between the two experiments as well as with the previous studies. The form-factor parameter precision has been substantially increased with respect to the previous experimental results. This work was supported by the Russian Foundation for Basic Research (project nos. 16-29-13014 and 19-02-00097).
Precision measurements of $\beta$-spectra have always been and are still playing an important role in several fundamental physical problems, predominantly in neutrino physics. In Petersburg Nuclear Physics Inst. NRC KI, the $\beta$-spectra of $^{144}{\rm{Ce}}-^{144}{\rm{Pr}}$ nuclei were measured with aim to determine the spectrum of electron antineutrinos. The artificial source of antineutrinos $^{144}{\rm{Ce}}-^{144}{\rm{Pr}}$ is one of the most promising for the experiments on the search for neutrino oscillations to the sterile state [1]. Several $\beta$-spectrometers based on silicon detectors have been developed. The first $\beta$-spectrometer, based on full absorption Si(Li) detector and thin transmission detector, allows to perform efficient separation $\beta$-radiation and accompanying X-rays and $\gamma$-radiation [2,3].
A new $\beta$-spectrometer was created from two Si(Li) detectors with a sensitive region thickness of more than 8 mm [4]. The response function of such a spectrometer for electrons with an energy of less than 3 MeV is almost Gaussian. The setup includes a 3" BGO detector for detecting gamma rays in order to select the decays of $^{144}{\rm{Ce}}-^{144}{\rm{Pr}}$ nuclei into excited levels of daughter nuclei. As a result, the beta spectra of $^{144}{\rm{Ce}}-^{144}{\rm{Pr}}$ nuclei were measured and the spectra of electron antineutrinos corresponding to $\beta$-transitions to the main and excited states. The measured form of the allowed $\beta$-transition is completely consistent with theoretical calculations. The created spectrometer with a response function close to Gaussian practically solves the problem of determining the spectrum of electronic antineutrino arising in the $\beta$-decay of $^{144}{\rm{Pr}}$ nuclei. The spectrometer can also be used in precision measurements of the spectrum shape of various radioactive nuclei.
This work was supported by the Russian Science Foundation (project nos. 17-12-01009) and by the Russian Foundation for Basic Research (project nos. 16-29-13014, 19-02-00097 and 20-02-00571).
[1] A.V. Derbin, I.S. Drachnev, I.S. Lomskaya, V.N. Muratova, N.V. Pilipenko, D.A. Semenov, E.V. Unzhakov, Monte-Carlo sensitivity study for sterile neutrino search with $^{144}{\rm{Ce}}-^{144}{\rm{Pr}}$ source and liquid scintillation detectors of various geometries, arXiv:1905.06670 (2019 г.)
[2] I.E. Alexeev, S.V. Bakhlanov, N.V. Bazlov, E.A. Chmel, A.V. Derbin, I.S. Drachnev, I.M. Kotina, V.N. Muratova, N.V. Pilipenko, D.A. Semenov, E.V. Unzhakov, V.K. Yeremin, Beta-spectrometer with Si-detectors for the study of $^{144}{\rm{Ce}}-^{144}{\rm{Pr}}$ decays, Nuclear Inst. and Methods in Physics Research, A 890 (2018) 64–67
[3] N.V. Bazlov, S.V. Bakhlanov, A.V. Derbin, I.S. Drachnev, V.K. Eremin, I. M. Kotina, V.N. Muratova, N.V. Pilipenko, D.A. Semenov, E.V. Unzhakov, E.A. Chmel, A Beta Spectrometer Based on Silicon Detectors, Instruments and Experimental Techniques, 2018, Vol. 61, No. 3, pp. 323–327
[4] S. Bakhlanov, A. Derbin, I. Drachnev, I. Kotina, I. Lomskaya, V. Muratova, N. Niyazova, D. Semenov, E. Unzhakov, 4$\pi$ semiconductor beta-spectrometer for measurement of 144Ce { 144Pr spectra, Journal of Physics: Conference Series 1390 (2019) 012117
Modern experiments with aim of investigation or search of ultra-rare events, for example neutrino or dark matter interaction within a low background detector, place high demands for the radiation purity of the materials used, even for those used in small quantities. These include materials used for soldering elements in detector systems, i.e. a solder and flux. Radioactive purity of the materials is crucially important since their location in a close proximity to the detector's body inside of the shields. Radionuclide purity of commercial solders does not meet the requirements because they are made of natural lead which contains the radioisotope 210Pb (T1/2 = 22.3 y.) on a level of 1÷100 Bq/kg.
In this paper we report on the preparation of solder with the composition: 60% Sn and 40% Pb, made from marketable tin with a chemical purity of 99.9999% [1] and raw archaeological Roman lead [2]. The investigation of the chemical purity of archaeological lead was performed in [3]. Two ingot tin-lead solders with a mass of 100 grams each were produced. In addition, for comparison of measurements, a sample of the same weight was made from commercial lead with a chemical purity of 99.9999% and high-purity tin. The solder fabrication work was carried out in a specially equipped clean room in JINR (Dubna), and measurements of the solder radioactivity levels were carried out in the Modane underground laboratory using a low-background HPGe detector Obelix.
In recent years, studies based on the application of the natural sciences methods on archaeological research have become increasingly important. The number of research programs on studying the cultural heritage of various eras is increasing. Still continues the development of different modern techniques for non-destructive analysis of the elemental and structural composition of ancient materials, their age and origin.
Neutron activation and XRF analysis are promising methods for analyzing of element content of archaeological materials. In present work the results of studies on development of instrumental neutron activation and X-ray fluorescence analysis of archaeological materials and fragments of meteorites are presented. Also the results of analysis of archaeological finds and fragments of the meteorite using the developed techniques are presented.
The quantitative composition of the meteoritic matter, which can be attributed to carbonaceous chondrites, is determined. Analysis of archaeological finds: according to the quantitative content of certain elements, all archaeological finds (ring, coin, bell, deer-form candlestick) can be attributed to the Bronze Age.
Spectroscopic factors are intensely used in the analysis of nuclear reactions. However, spectroscopic factors are absent in the rigorous theory of nuclear reactions. They arise only within the standard version of the distorted-wave Born approximation (DWBA) as a result of the replacement of a rigorous many-particle overlap function by a two-body wave function. This approach has no serious theoretical justification and is essentially a convenient method for approximate modeling of experimental data on direct nuclear reactions. Even within this approach, the accuracy of the spectroscopic factors extracted from the experimental data is low, especially in the case of the removal of composite objects, say, α-particles. Spectroscopic factors are off-shell quantities. They are not determined by the S matrix unlike on-shell quantities, such as phase shifts, binding energies, etc. It should be noted that, in contrast to spectroscopic factors, asymptotic normalization coefficients, which are currently actively used in the physics of nuclear reactions, are on-shell quantities. Spectroscopic factors are non-invariant under the unitary transformations of nuclear forces conserving the S matrix. Therefore, they are ‘non-observables’ which can only be defined within a special convention, like a particular form of the nuclear Hamiltonian which is used to derive or calculate them [1, 2]. Thus determining spectroscopic factors from experimental data is of rather limited value. Spectroscopic factors can be calculated in the framework of microscopic approaches. However, comparing the results of such calculations with the phenomenological values of spectroscopic factors is unlikely to provide any significant information.
This work was supported by the Russian Foundation for Basic Research grant No. 19-02-00014.
1. R.J.Furnstahl, H.- W.Hammer // Phys. Lett B 2002. V.531. P.203.
2. A.M.Mukhamedzhanov, A.S.Kadyrov // Phys. Rev. C 2010. V.82. 051601.
A structure of atomic nuclei have many examples of a phase transitions with increase of the excitation energy, rotational moment and changing of the number of nucleons. These are phase transitions in the equilibrium shape and structure of the ground and low-lying excited states related to symmetry changed. The problem of phase transitions has caused of new wave of researches of the structure of atomic nuclei. In the review are considered different examples of nuclear phase transitions. Description of phase transitions in collective nuclear model and microscopic aspects of phase transitions are discussed.
The problem of significant disagreements [1] between partial photoneutron reaction cross sections obtained using the method of neutron multiplicity-sorting at Livermore (USA) and Saclay (France) was investigated in detail. As a rule for 19 nuclei from $^{51} \mathrm{V}$ to $^{238} \mathrm{U}(\gamma, 1 \mathrm{n})$ reaction cross sections are larger at Saclay, but $(\gamma, 2 n)$ cross sections vice versa larger at Livermore. The averaged Saclay/Livermore ratio $\mathrm{R}=\sigma_\mathrm{S}^{\text {int }} / \mathrm{\sigma_L}^{\text{int}}$ of integrated cross sections is equal to $\mathrm{R}_{1}=1.08$ for $(\gamma, 1 \mathrm{n})$ reaction but $\mathrm{R}_{2}=0.83$ for $(\gamma, 2 \mathrm{n})$ reaction.
Using the objective physical criteria for data reliability [2] it was found that there are several quite different reasons for systematic uncertainties obtained. For many nuclei it was shown that the main reason of those is unreliable sorting of many neutrons between $1 \mathrm{n}, 2 \mathrm{n}$ and, $3 \mathrm{n}$ channels because of definite shortcoming of the method of neutron multiplicity-sorting [1,2]
Four very interesting cases were investigated in detail: data for three nuclei for which the differences between $\mathrm{R}_{1}$ and $\mathrm{R}_{2}$ are very large $\left(^{127} \mathrm{I}\left(\mathrm{R}_{1}=1.34\right.\right. $ and $\left.\mathrm{R}_{2}=1.08\right), ^{181}\mathrm{Ta}(1.25$ and $0.89),$ and $\left. ^{208}\mathrm{Pb}(1.22 \ \mathrm{ and } \ 0.77) \right)$ and for $^{75}\mathrm{As}$ for which those ratios are also large but very close to each other, $\mathrm{R}_{1} \approx \mathrm{R}_{2} \approx 1.22 .$ For all four nuclei mentioned the neutron yield reaction cross sections $(\gamma, \mathrm{xn})=(\gamma, 1 \mathrm{n})$ $+2(\gamma, 2 \mathrm{n})+3(\gamma, 3 \mathrm{n})+\ldots \quad$ obtained at Saclay and Livermore are significantly different at photon energies before the threshold B2n of $(\gamma, 2 n)$ reaction, where one has no multiplicity sorting problems. Using the experimental-theoretical method for evaluation of partial photoneutron reaction cross sections [2] it was shown that the main reason of such type significant differences of data is that at Livermore many neutrons from the reaction $(\gamma, 1 \mathrm{n})$ were lost.
In the case of nucleus $^{51}\mathrm{V}$[3,4] it was found that additionally to unreliable sorting of many neutrons between $1 \mathrm{n}, 2 \mathrm{n}$ and, $3 \mathrm{n}$ channels because of definite shortcoming of the method of neutron multiplicity-sorting the another reason for systematic disagreements is that the contribution of proton reaction $(\gamma, 1 \mathrm{n} 1 \mathrm{p})$ was not taken into account.
Total reaction cross sections for interaction of ${}^8$Li and ${}^8$He secondary beam with ${}^{28}$Si, ${}^{59}$Co, ${}^{181}$Ta target nuclei in the energy range 25–45 A MeV were measured. Modified transmission method based on registration of prompt $n$, $\gamma$ radiation by a multi-detector $\gamma$-spectrometer [1, 2] was used. Energy dependences of total reaction cross sections were obtained. Theoretical analysis of experimental data was performed in the microscopic model based on numerical solution of the time-dependent Schrödinger equation for the outer weakly bound neutrons of the projectile nucleus [3]. Agreement with experimental data was obtained. The role of the cluster structure of projectile nuclei [4] in the reaction mechanisms was analyzed.
Referances
1. Yu.E. Penionzhkevich, Yu.G. Sobolev, V.V. Samarin, M.A. Naumenko // Phys. Rev. C. 2019. V.99. 014609.
2. Yu.G. Sobolev, Yu.E. Penionzhkevich, V.A. Maslov et al. // Bull. Russ. Acad. Sci.: Phys. 2019. V. 83. P. 402.
3. V.V. Samarin // Phys. At. Nucl. 2015. V. 78. P. 128.
4. V.V. Samarin, M.A. Naumenko // Bull. Russ. Acad. Sci.: Phys. 2019. V. 83. P. 411.
Recently unique experiments have been carried out to measure the fully (FDCS) and single (SDCS) differential cross sections of Compton ionization of helium atoms near the threshold of single ionization [1]. The photon energy was about 2 keV, and the energy of the detected electrons did not exceed 10 eV.
An adequate theoretical description in this energy range can be carried out in the framework of the so-called $A^2$ approximations. The corresponding matrix element looks exactly like the usual first Born approximation (FBA) in the case of ionization of an atom by a fast particle (electron, proton, heavy ion). This analogy allows us to treat the process under consideration on a par with such well-known methods of spectroscopy of the outer shells of atoms and molecules as (e, 2e), (p, pe), etc. It should be noted that the contribution to the second-order matrix element of the term including two sequential dipole transitions is extremely small in this kinematic region, which makes Compton ionization a valuable spectroscopic tool.
The sequential $n$-stage ($n\geq2$) decay of the compound nucleus $A$: $A \rightarrow {b_1}+A_1 \rightarrow \ldots \rightarrow {b_1}+\ldots +{b_n}+A_n$ with the formation of the real particles $b_1, \ldots, b_n$, intermediate nuclei $A_1,\ldots, A_{n-1}$ and the final nucleus $A_n$ with internal energies $E_{b_1},\ldots, E_{b_n}$ and $E_{A_1},\ldots,E_{A_n}$, correspondingly, has been considered. It has been proved that the width of mentioned decay can be presented by the integral of productions of the $i$-stage widths, corresponding to the real and virtual processes. If the $i$-th stage of the decay has the decay heat $\left( E_{A_i}-E_{A_{i+1}}-E_{b_{i+1}} \right)<0$, then this decay stage has virtual character and can be described using the formalism [1]. If the $i$-th stage of the decay has the positive decay heat $\left( E_{A_i}-E_{A_{i+1}}-E_{b_{i+1}}\right)>0$, then this decay is really observed and can be described by the $R$-matrix theory of nuclear reactions [2].
In [3] it was shown that the experimental characteristics of spontaneous ternary fission of $^{248}$Cm, $^{250}$Cf, $^{252}$Cf [4] with emission of $\alpha-$particle as the third particle, are adequately described using the representation about two-stage character of this fission, when on the first stage the long-ranged $\alpha$-particle is emitted from the neck of the fissile nucleus $A$ and the virtual state of the intermediate nucleus $(A-4)$ is formed, and on the second stage this nucleus $(A-4)$ decays onto two fission fragments. In present paper by usage of methods [3] it has been demonstrated that the characteristics of the induced by thermal neutrons ternary fission of $^{233}$U and $^{235}$U are successfully described on the base of virtual mechanism. It has been obtained that fissile nucleus neck radii $r_A$ for induced fission of compound nuclei $^{234}$U and $^{236}$U are close to the analogous neck radii for spontaneous fission of $^{248}$Cm, $^{250}$Cf, $^{252}$Cf and are in good agreement with the estimations of the theoretical models considering fissile nucleus deformations.
The differential cross section $\sigma(\theta)$ of the ternary fission of actinide nuclei by cold polarized neutrons can be presented as a sum of the terms of null order $\sigma ^0(\theta)$ and the first order $\sigma ^1(\theta)$ on the neutron polarization vector $\vec{p}_n$: $\sigma(\theta)=\sigma ^0(\theta)+\sigma^1(\theta)$ (1), where $\theta$ is an angle between the directions of flights of the third particle and light fragment. In general case $\sigma^1(\theta)$ can be presented as sum of the triple $\sigma^1_3(\theta)$ and quinary $\sigma^1_5(\theta)$ correlators, which satisfy the conditions: $\sigma_3^1(\theta)=\sigma_3^1(\pi-\theta),\sigma_5^1(\theta)=-\sigma_5^1(\pi-\theta)$ (2). These components $\sigma^1_3(\theta)$ and $\sigma^1_5(\theta)$ can be calculated using experimental differential cross sections $\sigma(\theta)$ and $\sigma ^0(\theta)$ in (1) and formula (2). In quantum fission theory [5,6] $\sigma^1_3(\theta)$ and $\sigma^1_5(\theta)$ have forms:
$\sigma_3^1(\theta)=\Delta^{{odd}}\frac{d{\sigma}_0^{odd}(\theta)}{d\theta}$, $\sigma_5^1(\theta)=\Delta^{{even}}\frac{d{\sigma}_0^{even}(\theta)}{d\theta}$ (3), where $\sigma_0^{odd}(\theta)$ and $\sigma_0^{even}(\theta)$ are components of $\sigma_0$ defined by sums over spherical functions with odd and even orbital momenta, correspondingly, and $\Delta$ is an angle, which characterizes the changing of the angle $\theta$, which takes into account the influence of the connected with the collective rotation of the fissile nucleus Coriolis interaction on the directions of the light fragment and ternary particle flight. Using the experimental values of the cross section $\sigma^0(\theta)$ it is possible to calculate by formulae (3) the angles $\Delta^{{odd}}$ and $\Delta^{{even}}$ for various ternary fission types. In [5,6] it has been shown that for the ternary fission of $^{233}$U and $^{235}$U with the emission of the $\alpha$-particle the angles $\Delta_{\alpha}^{odd}$ are positive, but the angles $\Delta_{\alpha}^{{even}}$ change their sign under the transition from $^{235}$U to $^{233}$U. At the same time the calculation on the base of the trajectory methods [7] use the parametrization: $\sigma_3^1(\theta)=C$; $\sigma_5^1(\theta)=\sigma^1(\theta)-C$, where $C$ is a constant, and $\sigma_5^1(\theta)$ concides with (3), the angles $\Delta_{\alpha}^{{even}}$ and $\Delta_{\alpha}^{{odd}}$, are correctly describe the signs of $\Delta_{\alpha}^{{odd}}$ for $^{233}$U and $^{235}$U, but conserve the same signs of $\Delta_{\alpha}^{{odd}}$ for $^{233}$U and $^{235}$U that critically contradicts to the fact of sign changing in the experiment. For the ternary fission accompaning with evaporative neutrons and $\gamma$-quanta from the fission fragments the $\sigma^0$ have only even orbital momenta, and the angles $\Delta_{n}^{even}$ and $\Delta_{\gamma}^{{even}}$ are defined by the influence of the Coriolis interaction onto fission fragments because of its small values in the region of these neutrons and $\gamma$-quanta emission. Using the experimental data [8] of the $\Delta_{n}^{{even}}$ and $\Delta_{\gamma}^{\textrm{even}}$ change the value under the transition from $^{233}$U to $^{235}$U, that is in agreement with the experimental sign change of $\Delta_{\alpha}^{{even}}$ for $\alpha$-particle. This fact approve the correctness of the experimental results [8].
References
S.G. Kadmensky, Yu.V. Ivankov, D.E. Lubashevsky // Phys. Atom. Nucl. 80, 903 (2017).
A.M. Lane, R.G. Thomas // Rev. Mod. Phys. 30, 257 (1958).
S.G. Kadmensky, L.V. Titova, D.E. Lyubashevsky // Phys. of At. Nucl., 83, 581 (2020).
M. Mutterer and J. P. Theobald, Dinuclear Decay Modes, Bristol: IOP Publ., 1996, Chap. 12.
S.G.Kadmensky, V.E. Bunakov, D.E.Lubashevsky // Phys. of At. Nucl. 81, 433 (2018).
S.G.Kadmensky, D.E.Lubashevsky, P.V. Kostryukov, // Phys. of At. Nucl. 82, 252 (2019).
A.Gagarsky et al. // Phys. Rev. C. 93, 054619 (2016).
G.V.Danilyan et al. // Phys. of At. Nucl. 77, 715 (2014).
Recent developments of the relativistic nuclear field theory (NFT) on the fermionic correlation functions will be presented. The general non-perturbative equation of motion framework is formulated in terms of a closed system of non-linear equations for one-body and two-body propagators. The present formulation provides a direct link to ab-initio theories and extends the explicit treatment of many-body correlations beyond the standard NFT level. The novel approach to the nuclear response, which includes configurations with two quasiparticles coupled to two phonons (2q⊗2phonon), is discussed in detail for electromagnetic excitations in medium-mass nuclei. The proposed developments are implemented numerically on the basis of the relativistic effective meson-nucleon Lagrangian and compared to the models confined by 2q and 2q⊗phonon configurations, which are considered the state-of-the-art for the response theory in nuclear structure calculations. The results obtained for the dipole response of $^{42,48}$Ca and $^{68}$Ni nuclei in comparison to available experimental data show that the higher-complexity configurations are necessary for a successful description of both gross and fine details of the spectra in both high-energy and low-energy sectors.
The approach confined by the 2q⊗phonon configurations has been extended recently to the case of finite temperature for both neutral and charge-exchange nuclear response. Within this approach, we investigate the temperature dependence of nuclear spectra in various channels, such as the monopole, dipole, quadrupole and spin-isospin ones, for even-even medium-heavy nuclei. The special focus is put on the giant dipole resonance’s width problem, the low-energy strength distributions and the influence of temperature on the equation of state. The temperature dependence of the Gamow-Teller and spin dipole excitations will be discussed in the context of its potential impact on the astrophysical modeling of supernovae and neutron-star mergers.
Shape coexistence is a remarkable phenomena consisting in the presence in the same nucleus, within the narrow energy range, of two or more states which have distinct properties and can be interpreted in terms of different intrinsic shapes [1]. Recently accumulated experimental data have shown that $^{96}$Zr has coexisting spherical and deformed structures with small mixing amplitudes. The observed properties of the low-lying collective states in $^{96}$Zr was investigated in the frame of the geometrical collective model by diagonalization of the quadrupole collective Bohr Hamiltonian. Good agreement with the experimental data on the excitation energies, B(E2) and B(M1) reduced transition probabilities is obtained. It is shown that the low-energy structure of $^{96}$Zr can be described in a satisfactory way within the geometrical collective model with a potential function supporting shape coexistence without other restrictions of its shape [2].
[1] J. E. García-Ramos and K. Heyde. Phys. Rev. C 100, 044315 (2019)
[2] D. A. Sazonov, E. A. Kolganova, T. M. Shneidman, R. V. Jolos, N. Pietralla, and W. Witt. Phys. Rev. C 99, 031304(R) (2019)
An extension of the self-consistent theory of finite Fermi systems [1,2] to the energy region of pygmy- and giant resonances in magic nuclei is performed with the aim to consider particle-hole (ph) and complex 1p1h⊗phonon configurations and to consistently account for the phonon coupling (PC) .
A new equation for the effective field, which determines nuclear polarizability,
has been derived. Quite new PC contributions to the effective field, which are of interest in the energy regions of PDR and GMR, have been obtained. These contributions are the following. 1) The tadpole effect in the standard ph-propagator. In order to calculate dynamic tadpole contributions, it is necessary to solve the equation for the two-phonons creation amplitude or, maybe, to use the known estimations for the tadpole. 2) Two new interactions induced due to phonon exchange in the second ph-channel (in addition to the old phonon-exchange interaction in the first ph-channel) and the phonon-exchange interactions in the pp- and hh-channels, 3) The effects of the first and second variations of the effective interaction in the phonon field. Such an extension allows us to describe on the equal footing both the ground states and the whole region of nuclear excitations up to giant resonances energies (30-35 MeV). The qualitative analysis and discussion of the new terms are performed.
A. B.Migdal, Theory of Finite Fermi Systems and Applications to Atomic Nuclei (Nauka, Moscow, 1965; Intersci., New York, 1967).
V. A. Khodel and E. E. Saperstein, Phys. Rep. 92,183 (1982).
The presence of an energy gap in the spectrum of single nucleon states of even-even nuclei facilitates the identification of collective excitations corresponding to a change in the surface shape and rotation of atomic nuclei. In odd atomic nuclei, the energy of single-nucleon excitations usually differs little from the energy of collective excitations; therefore, their separation is possible only in some special cases. The interaction between the rotation of the nucleus and the external nucleon, on the one hand, changes the structure of the rotational spectrum corresponding to the adiabatic approximation, on the other hand, this interaction changes the spectrum of single-particle excitations. The above circumstances make it difficult to classify the excited states of odd nuclei by analogy with the classification of the excited states of even-even nuclei. And the excited collective states of odd-odd nuclei are even more complex and is an interesting subject, and this phenomenon has been little studied.
In the non-adiabatic collective model, where the Hamilton operator includes the operators of longitudinal and transverse vibrations of the surface of an even-even remainder and the energy operator of an external proton and neutron in the core field, the interactions of an external proton and neutron are also taken into account. However, the general solution of the Schrodinger equation by such a Hamiltonian is complex. Therefore, the present work attempts to describe the collective excitations of odd-odd nuclei in the framework of a non-adiabatic collective model with effective non-axiality. The rotationally single-nucleon spectrum of the excited states of odd-odd nuclei is determined. These states were calculated and compared with experimental data for nuclei ${}^{100}$Y, ${}^{104}$Rb, ${}^{162,164}$Ho, ${}^{242}$Am.
$\mathrm{Vlasnikov A.K.}, \fbox{Zippa A.I.}, \mathrm{Mikhajlov V.M.}$,
St. Petersburg State University, St. Petersburg, Russia
E-mail: a.vlasnikov@spbu.ru
If an ideal energy surface around a deformed nucleus with even $N$ and $Z$
existed and were linear and quadratic in deviations $s$ and $t$ from $N$ and $Z$
respectively $(|s| / N \ll 1,|t| / Z \ll 1)$
$\begin{aligned} E(N+s, Z+t)=M &(N+s, Z+t)-m_{n}(N+s)-m_{p}(Z+t)=\mathscr{E}(N, Z)+d_{1 n} s+d_{1 p} t+\\ &+d_{2 n} s^{2} / 2+d_{2 p} t^{2} / 2+d_{1 n 1 p} s t \end{aligned}$
$\left(E, M \text { are nuclear energy and mass, } m_{n}, m_{p}\right.$ are nucleon masses), then parameters $\mathscr{E}(N, Z)$ and $d_{\text {inkp }}$ should not depend on those adjacent nuclei which are used for calculations of these parameters. In particular, a measured $E(N, Z)$ has to coincide with a calculated parameter $\mathscr{E}(N, Z) .$
For determination of $E(N, Z)-\mathscr{E}(N, Z)$ and other parameters three groups of even-even nuclei are applied: $s$ -Appr. (Approximation, $s=\pm 2,\pm 4, t=0,$ i. e. isotopes); $t$ -Appr. $(s=0,$ $t=\pm 2,\pm 4, \text { i.e. isotones })$ and $(s t)-$ Appr. in which $s=\pm 2, t=\mp 2 ; s=\pm 4, t=\mp 4$
Calculated quantities $E(N, Z)-\mathscr{E}(N, Z)$ are given in Table $[1],$ which shows
that these quantities are sign variable in different approximations and a maximum divergence attains $\simeq 120 \mathrm{keV} .$ Approximately the same difference is found in other parameters. Thus, description of the energy surface around a deformed even-even nucleus by Eq. (1) is rather approximate. This information is useful for prediction of unknown masses and calculations of the pairing energies.
The reported study was funded by RFBR, project number 20-02-20032.
Estimation of the surface tension coefficients in the even-even nuclei could be performed due to connection of surface tension and nuclear rigidity [1]. The values of rigidities are connected with the mean squared deformations of nuclei [2]. The estimation of the surface tension coefficients in the even-even nuclei were presented in [3]. The coefficients $\sigma$ show great fluctuations: from $\sigma \approx$ 1.0÷1.8 (for 150<$A$<198) up to $\sigma$ ≈ 34 MeV/$\text{fm}^2$ (for $^{208}\text{Pb}$, $^{210}\text{Pb}$). The comparison of these values with the data on nuclear charge radii reveals the impact of the filled out neutron shell peculiarities on $\sigma$.
In the figures the calculated [3] surface tensions for Calcium and Zirconium isotopes together with the values of $r_0$ coefficients are shown. The surface tension in nuclei is highly influenced by the shell structure, especially of the neutron subshells near the surface: $(1d_{3/2})_n^4(1f_{7/2})^8_n$ for $^{48}\text{Ca}$ and $(1g_{9/2})^{10}(2d_{5/2})^6$ for $^{96}\text{Zr}$ . The highest $\sigma$ corresponds as well to the highest values of pressure $p$ (according to the Laplace formula $p \approx \frac{2 \sigma}{R}$). It is obvious that filling out two near neutron subshells leads to grow of pressure on the proton component of the nuclei and, as consequence, to decreasing of the charge radii.
For $^{208}\text{Pb}$ and $^{210}\text{Pb}$ the surface tension is close to the maximum among all even-even nuclei ($\sigma \approx$ 34 MeV/$\text{fm}^2$). It is approximately $0.75 \cdot 10^{20}$ higher than $\sigma$ for water at 20 $^\text{o}$C.
References
[1] A. Bohr // Dan.At.Fys.Medd. 22, #14, 7 (1952)
[2] S. Raman ea// At.Data & Nucl.Data Tabl. 78, 1 (2001)
[3] N.G. Goncharova //PEPAN 50,#5,532 (2019); N.G. Goncharova, A.P. Dolgodvorov //Moscow Univ.Bull.69#3(2014)
In recent years, several successful applications of the Artificial Neural Networks (ANNs) have emerged in nuclear physics, high-energy physics, and other fields of science. These works have already shown, that modeling of nuclear data with ANNs provides a valuable complementary approach to theory-driven models of the systematics of nuclear data (see e.g. [1] and references therein). A significant effort to exploit these novel methodologies is motivated by aspirations toward experimental and theoretical exploration of nuclei far from stability.
In our work we aimed at predicting the binding energies {$B/A$}, as well as the two-proton and two-neutron separation energies ($S_{2p}$, $S_{2n}$) of super-heavy nuclides, specifying only their proton and neutron numbers ($Z, N$) together with the numerical parity of the latter. Given a body of training data [2] the iRPROP (improved resilient backpropagation) and Adam (adaptive moment estimation) learning algorithms have been used to adjust the parameters of the deep ANN, determining (without any further theoretical assumptions) the mapping from the proton and neutron numbers to the properties of the nuclear ground state.
The predictive power of the neural network emerging from simulations done within the Keras+TensorFlow framework is compared with that of traditional phenomenological models. The obtained results show not only excellent learning performance of our network (with the MSE deviation between the ANN output and the 2498 experimentally known binding energies at the level of 70 eV), but are also very promising in predictions of various properties of both super-heavy nuclei as well as nuclei far from stability. It is found that the purely phenomenological models, based on deep ANNs can match or even surpass the predictive performance of conventional models for nuclear systematics (e.g. in grasping the existence of shell structure) and accordingly should provide a valuable additional tool for exploring the expanding nuclear landscape.
We had suggested in our previous publications (see, e.g. [1-2]) the definition of quantum chaos based on the Liouville-Arnold theorem. It states that a system featuring N degrees of freedom is regular if it has M = N linearly independent ﬁrst integrals of motion in involution. First (global, isolating) integrals of motion are those that, by Noether’s theorem, are associated with the symmetry of the system (that is, with the presence of a group of transformations under which the Hamiltonian of the system is invariant). Therefore, it is natural to deﬁne a chaotic quantum system as that whose symmetry is so low that the number M of its good quantum numbers is smaller than the number N of its degrees of freedom. We had also stressed [3] that only the Wigner distribution law might be a true signature of the system’s hard chaos, while the popular belief about the Poisson level distribution for the regular system is wrong and misleading.
Therefore, we suggested a rather simple way to find whether the quantum system under consideration is chaotic: just to compare the number N of its degrees of freedom with the number M of its integrals of motion (good quantum numbers). If the system’s symmetry is so low that the number of its integrals of motion is smaller than the number of its degrees of freedom, then it is chaotic.
However, Noether’s theorem is proved only for continuous transforms while in quantum mechanics we face also symmetries arising from discrete transforms, like space and time inversion. The question is whether presence of these symmetries should be taken into account in the above analysis of system’s chaoticity.
We demonstrate that an additional good quantum number of parity plays a role of an integral of motion and should be taken into account in calculating M. Time-reversal invariance does not generate any corresponding good quantum number (or integral of motion).
Yields from the complete fusion reaction of 40Ar + 144Sm => 184-xnHg were measured by the catcher foil method [1] (on the U400M cyclotron at the Flerov Laboratory of Nuclear Reactions). Cross sections for neutron channels of complete fusion were calculated from measured yields. The catchers were made out of five aluminum foils (0,8 µm thick) stacked downstream from the target. The experiment was carried out in repetitive short cycles (10 s). The foils were periodically moved from the beam position to the detector position. Data from the detector were analyzed to obtain α-spectra of implanted isotopes.
The talk will be focused on the data analysis of the above mentioned reaction. As a rule, the α-particle spectra produced in these types of experiments have a very complicated structure. The problem of resolving them into separate lines attributed to specific decaying nuclides can be rather complicated. To make it easier, new software written in LabVIEW was developed. It allows one to calculate the cross sections of the reaction studied by taking into account all essential corrections: half-life and α-decay probability of the registered isotopes, and also the influence of measurement cycles. Geometric efficiency of the detectors was simulated using GEANT4 software. The current of the incident ion beam was measured. The energy of the ion beam from the cyclotron was decreased by a degradation foil upstream of the target. Straggling of the ion beam in both the degradation foil and the target itself were experimentally measured.Measured energy dispersion was higher than what theory predicted. Therefore, deconvolution of the incident excitation function was applied on the obtained results. Experimental results were compared with theoretical excitation functions from the channel coupling model.
Experimental results were compared with results obtained on the MASHA setup (Mass Analyzer of Super-Heavy Elements) [2] to allow estimation of time and separation efficiency of mass spectrometer MASHA.
The search for super-asymmetric fission, has been receiving increasing interest due to its possible interest in producing exotic neutron rich nucleus [1]. Among the four main fission modes prescribed by Brosa [2], the supershort mode manifests itself only when light and heavy fission fragments are close to the double magic tin with A~132 in their nucleon composition. Though the possibility of the fission asymmetry of the pre-actinides had been predicted in 70’s [3], it took a decade to substantiate this prediction experimentally [4]. Recently, the superasymmetric mode due to the influence of double magic Ca (Z = 20, N = 28) and double magic Pb (Z = 82, N = 126) has been observed at a mass yield level of 10-3 and 10-5, in fission of excited 260No compound nucleus, populated by the reactions 12C+248Cm and 22Ne+238U, respectively [5, 6]. The fission mass distributions of the fermium isotopes showed a marked transition from asymmetric to symmetric as the mass number increases from 254 to 258 [7]. Additionally, Lustig et al. [8] predicted super-asymmetric fission modes in 253Fm(n,f) 254Fm(sf). So, further investigations at the lower excitation energies of Fm isotope and to discern super-asymmetric fission mode and its characteristics out of all other fission modes, was of paramount importance.
The mass-energy distributions of fission fragments of 254Fm compound nucleus formed in the reaction 16O+238U have been measured at two lab energies Elab = 89 and 101 MeV, using the two-arm time-of-flight spectrometer CORSET [9]. The contribution from quasifission is negligible in the reaction 16O+238U [10]. At the energy close to the Coulomb barrier (corresponding excitation energy ECN~ 45 MeV), where the shell effects still exist, the enhancement of the mass yield in the region 60-70 u for the light fragment is observed. This can be explained by the influence of double magic Ni (Z=28, N=50). The mass yield is found to be around 10-2 %. This signature of super-asymmetric fission goes away at the higher excitation energy (ECN~ 56 MeV).
[1] M.Huhta et al., Phys. Lett. B 405, 220 (1997).
[2] U.Brosa, S.Grossmann and A.Muller, Phys. Rep. 197, 167 (1990).
[3] V.V.Pashkevich, Nucl. Phys. A 169, 275 (1971); M.G.Mustafa et al., Phys. Rev. C 7, 1519 (1973).
[4] G.Barreau et al., Nucl. Phys. A 432, 411 ( 1985); M.G.Itkis et al., Z. Phys. A 320, 433 (1985); C.Budtz -Jørgensen, H.-H.Knitter, Nucl. Phys. A 490, 307 (1988).
[5] G.Knyazheva et al., EXON-2012-Proceedings of the International Symposium, 167 (2013).
[6] K.B.Gikal et al., Bulletin of the Russian Academy of Sciences: Physics, 82, 716 (2018).
[7] J.E.Gindler et al., Phys. Rev. C 16, 1483 (1977); R.M.Harbour et al., Phys. Rev. C 8, 1488 (1973); R.C.Ragaini et al., Phys. Rev. C 9, 399 (1974).
[8] H.J.Lustig, J.A.Maruhn and W.Greiner, J. Phys. G : Nucl. Phys. 6, L25 (1980).
[9] E.M.Kozulin et al., Instrum. Exp. Tech. 51, 44 (2008).
${E.Galkina^\textit{1}}$, ${E. M. Kozulin^\textit{1}}$,${G. N. Knyazheva^\textit{1}}$ , ${I. M. Itkis^\textit{1}}$, ${A. A. Bogachev^\textit{1}}$, ${I. N. Diatlov^\textit{1}}$, ${M. Cheralu^\textit{1}}$, ${D. Kumar^\textit{1}}$, ${N. I. Kozulina^\textit{1}}$,${ K. V. Novikov^\textit{1}}$, ${A. N. Pan^\textit{1,2}}$,${ I. V. Pchelintsev^\textit{1}}$, ${I. V. Vorobiev^\textit{1}}$,${ W. H. Trzaska^\textit{3}}$, ${S. Heinz^\textit{4}}$, ${ B. Lommel^\textit{4}}$, ${ E. Vardaci^\textit{5,6}}$, ${S. Spinosa^\textit{5,6}}$, ${A. Di Nitto^\textit{5,6}}$, ${ A. Pulcini^\textit{5,6}}$, ${ S. V. Khlebnikov^\textit{7}}$, ${C. Borcea^\textit{8}}$, ${I. Harca^\textit{8}}$, ${ D. M. Filipescu^\textit{8}}$
${^\textit{1}}$Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, 141980 Dubna, Russia
${^\textit{2}}$Laboratory of Fission Physics, Institute of Nuclear Physics, Almaty, 480082 Kazakhstan
${^\textit{3}}$Department of Physics, University of Jyväskylä, FIN-40014 Jyväskylä, Finland
${^\textit{4}}$GSI Helmholtzzentrum f ̈ur Schwerionenforschung, 64291 Darmstadt, Germany
${^\textit{5}}$Dipartimento di Fisica “E. Pancini”, Universita de li t di di Napoli “Federico II”, 80126 Napoli, Italy
${^\textit{6}}$Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, 80126 Napoli, Italy
${^\textit{7}}$Khlopin Radium Institute, St.Petersburg, Russia
${^\textit{8}}$Horia Hulubei National Institute for Physics and Nuclear Engineering, 077125 Bucharest- Măgurele, Romania
The present work is focused on exploring the features of fission of ${^\text{264}}$Sg formed in the reaction ${^\text{32}}$S+${^\text{232}}$Th at energies near and below the Coulomb barrier. The detailed study of properties of Sg fission will enrich the information on fission in the transition region of transactinide nuclei. The experiment was carried out at the K-130 accelerator of the University of Jyväskylä (Finland) at energies of ${^\text{32}}$S ions of 165, 181 и 200 MeV. The mass-energy distributions of the reaction fragments were measured using the double-arm time-of-flight spectrometer CORSET. As a result of the analysis of experimental data, the dependence of width of mass-energy distributions on the excitation energy was obtained. In the symmetric mass region (А/2±20), the contribution of the quasifission process was found at energies both below and above the Coulomb barrier.
This work was supported by a joint grant from the Indian Department of Science and Technology and the Russian Foundation for Basic Research (project No. 19-52-45023).
This work devoted to the study the mass and energy distributions of fission fragments to investigate the role of closed proton and neutron shells in the fission of 248,250Cf, 254,256Fm, and 260No nuclei [1,2,3,4] at excitation energies of 40–55 MeV. Experiments are performed on the U-400 cyclotron at the Flerov Laboratory of Nuclear Reactions (Dubna, Russia) using the CORSET double-arm time-of-flight spectrometer [5].
To study the role of the multimodal fission the mass and energy distributions of fission fragments formed in the reactions 16,18O+232Th, 238U, and 22Ne+232Th, 238U at energies around the Coulomb barrier have been measured. It was found that at these energies the mass and energy distributions of fragments exhibit the multimodal structure, which results in the larger variance of the mass distributions.
References:
[1] D.J. Hinde, D.Y. Jeung, E. Prasad et al. // Phys. Rev. C. 2018. V. 97. 024616.
[2] K. Banerjee, T.K. Ghosh, S. Bhattacharya et al. // Phys. Rev. C. 2011. V. 83. 024605.
[3] K. Nishio, H. Ikezoe, Y. Nagame et al. // Phy. Lett. B. 2004. V. 93. 162701. P.909.
[4] D.O. Eremenko, V.A. Drozdov, O.V. Fotina et al. // Phys. Rev. C. 2016. V. 94. 014602.
[5] E.M. Kozulin, A.A. Bogachev, M.G. Itkis et al. // Instrum. Exp. Tech. 2008. V. 51.P. 44
Important information on the structure of Super Heavy Elements (SHE) can come from the study of lighter deformed transfermium (Z ~ 100–106) elements. The cross-section for the formation of these nuclei is many orders of magnitude higher than for Z ≥ 110 so that detailed spectroscopy becomes possible.
The opportunity to have high intensity (>1 pμA) accelerated beams with A ≤ 50 together with the use of exotic targets provide the possibility to study many aspects of heavy ion induced reactions exploiting new generation of high efficiency, high resolution experimental setups.
In recent years α-, β- and γ- spectroscopy of heavy nuclei at the focal plane of recoil separators (“decay spectroscopy”) has been very intensively developed. The mixing of α decay with γ and β decay spectroscopy allows to investigate single particle states behavior as well as the structure of little known elements in the Z = 100–104 and N = 152–162 region.
Using SHELS recoil separator and GABRIELA (Gamma Alpha Beta Recoil Invetsigations with the ELectromagnetic Analyser) detector set-up the experiments aimed to the gamma and electron spectroscopy of the Fm – Db isotopes, formed at the complete fusion reactions with heavy ions 22Ne, 48Ca, 50Ti and 54Cr were performed at FLNR JINR.
At the years 2017–2019 we performed model experiments using method of high resolution alpha, EC and γ spectroscopy to study decay properties of 254,255,256,257Rf in the reactions 50Ti + 206,207,208Pb → 256,357,258Rf, 250,252,254No in the reactions 48Ca + 204,206,208Pb → 252,354,256No and 256No in the reaction 22Ne + 238U → 260No*.
Future developments and perspectives of experimental studies in spectroscopy of heavy and superheavy elements are discussed.
The consistent theoretical model for the calculations of the mass, charge and energy of fission fragment and the prompt fission neutron energy and multiplicity distributions [1, 2] is applied for the description of the spontaneous fission of the superheavy nuclei. The prompt fission neutron characteristics are formed during emission at descent from the fission barrier to the scission point and the evaporation from the fully accelerated heated fragment after neck rupture. The neutron emission during the saddle-to-scission descent time is important in the spontaneous fission of the heavy elements with Z > 96. For accurate calculations of nucleon composition and excitation energy of the fissioning nucleus at the scission point, the time-dependent statistical model with inclusion nuclear friction effects was used. Monte Carlo simulation method is used to describe the neutron emission at the limited descent time.
For each member of the compound nucleus ensemble at the scission point, the primary fission fragment characteristics: kinetic and excitation energies and their yields are calculated using the scission-point fission model with deformed nuclear shell and pairing effects. Isovector quantal excitations during the collective motion from saddle to scission point influence on the charge polarization and charge splitting between fission fragments. The charge distribution of the primary fragment isobaric chain was considered as result of the frozen quantal fluctuations of the isovector nuclear matter density at the finite scission neck radius in the harmonic approximation [3]. The collective isovector potential was calculated for the di-nuclear system of deformed fragment at the minimum of potential energy at scission point. The deformation energy at scission point is calculated using the macroscopic-microscopic approach. The average charge asymmetry and the stiffness parameter of the collective potential were obtained by the parabolic approximation of the calculated potential energy at the fixed mass asymmetry. The charge width of the fission fragment isobaric chain are determined mainly by the of collective ground-state wave function. Results of calculations of the spontaneous fission characteristics of the superheavy nuclei of element chains with 104 ≤ Z ≤ 118 will be presented.
Several experiments aimed to investigate properties of short-lived SF nobelium isotopes we carried out in FLNR. The neutron-deficient isotopes of nobelium were produced in fusion-evaporation reactions using 206,208Pb target and an intensive beam of 48Ca. Fusion-evaporation residues were separated by the SHELS separator and implanted into a large-area double-sided 48х48 strip silicon detector surrounded by 54 3He-counters of neutrons. The half-life and decay branching ratio for 252,254No is measured. The average number of neutrons per spontaneous fission of 254No is determined for the first time.
In this work the measurements of the differential cross sections (DCS) of the reaction 16O(10B,9Be)17F have been carried out at 10B ions beam of the C-200P cyclotron of the Heavy Ion Laboratory (University of Warsaw) with the energy E10B=41.3 MeV. The purpose of the experiment is to find out the suitability of this reaction near the Coulomb barrier to extract the ANC values to use in the calculations of astrophysical S- factors of proton radiative capture.
Thin Al2O3 self-supporting film with the thickness of ~0.15 mg/cm2 was used as a target. The charged particles were detected and identified by four ΔЕ-Е counter telescopes which were installed in the ICARE experimental chamber 1. The spectra were analyzed with the use of ROOT 2 software. A typical two–dimensional spectrum (ΔE, E) is shown in Fig. 1.
The analysis of the 16O(10B,9Beg.s.)17Fg.s. reaction by testing function R(b) of MDWBA approach [3] shows that the proton transfer has peripheral character at the forward hemisphere of the 9Be escape as the function R(b) is practically constant at varying the values of geometry parameters of the Woods-Saxon potential within the physically reasonable range (see Fig. 2). So the DCS of the reaction should be calibrated by the product of the ANCs squares (C10B→9Be+p)2×(C17F→16O+p)2 in accordance with MDWBA. As the ANC value C10B→9Be+p is rather well known from [4,5], one can obtain the ANC for the 17F→16O+p.
CLAS Physics Data Base (CLAS DB) has been developed in collaboration between the SINP at MSU and the Hall B at Jefferson Lab [1,2]. CLAS DB contains most experimental results on inclusive semi-inclusive and exclusive reaction off proton and nuclei obtained with the CLAS detector. The substantial part of these experimental results represent the only available in the world data sets. The results stored in the CLAS DB are of particular importance for exploration of the structure of the ground and excited hadron states offering the insight into strong QCD dynamics which underlie their generation from quarks and gluons [3,4]. The status of CLAS DB and the opportunities to use the available information for the research in hadron physics will be presented in the talk. In particular, the web-interface and the build-in tools for the customer data search and for extraction of semi-inclusive and exclusive structure functions in electron scattering will be presented. The work in progress on the development of the web resources for interpolation and extrapolation of inclusive/exclusive electron scattering observables [5] will be discussed.
References
1. CLAS Physics Data Base https://clas.sinp.msu.ru
2. V.V. Chesnokov et al., Memoirs of the Faculty of Physics 3, 199403 (2019).
3. V.D. Burkert, Ann Rev. Nucl. Part. Sci, 68, 405 (2018).
4. V.I. Mokeev, Few Body Syst. {59, 46 (2018).
5. A.N. Hiller Blin et al., Phys. Rev. C 100, 035201 (2019).
Nickel-63 is perspective isotope to produce microsized radioisotope power source [1]. Advantage of nickel-63 is combination of long half-life (T1/2 = 100 y), low beta-particle energies and absence of accompanying gamma-emissions. In industry nickel-63 is produced by nuclear reactor irradiation of nickel-62 [2].
Nickel-63 has been produced with nuclear power plant irradiation of nickel-62. Initial nickel abundance was 99.36% of nickel-62 and chemical purity - 99.9%. After nickel-62 irradiation for 300 days in a power nuclear reactor a product with abundance about 1.5% has been obtained. Production of nickel-63 was accompanying by accumulation of lateral gamma-radioactive isotopes (60Co, 46Sc, 59Fe, 65Zn, 51Cr, 117Sn, 54Mn, 124Sb) with activation of admixtures and via parallel nuclear reactions. The main doze-generating admixture was 60Co with specific activity 1 mCi/g of product.
In order to use nickel-63 as a power source it has to contain minimal amount of such radioactive admixtures. Radiochemical purification of nickel-63 from radioactive admixtures was based on the principle of volatile tetratrifluorophosphine of nickel [3]. This allowed to obtain product with contamination of lateral gamma-radioactive isotopes lower than 1 μCi/g.
Measured activity values of nickel-63 and its accompanied admixtures has been compared with calculated ones to verify a computer code to predict a future nickel 63 production with use of other nuclear reactors.
The spatial distribution of neutrons with the maximum energies from 3.3 to 5.3
MeV was investigated using a two-coordinate 10B detector. The detector was
located at the 119 cm distance from the 1000 cm3 beryllium target at the output of
on electron accelerator based photoneutron source. Between the 10B detector and
the target the collimator of 3 cm diameter was located. The contribution of slow
neutrons was suppressed by 0.5 cm thickness cadmium filter. The 3He counter
behind the 10B detector was used to take into account the contribution of the
background of slow neutrons. From the kinematics of the 9Be (γ, n) γ, n) 8Be reaction it
follows that an increase in gamma-ray energy by 1 MeV entails an increase in
neutron energy by 0.9 MeV.
The maximum intensity of the neutron flux measured along the horizontal axis
shifts back relative to the direction of the primary electron beam with increasing
electron energy and, accordingly, with the maximum neutron energy, as shown in
Fig. 1. The position of the maximum intensity of neutrons distribution is associated
with a maximum of neutron energy in the flux. In addition, one may note that the
width of the neutron intensity distribution in the flux increases with increasing
maximum neutron energy. It is possible that these effects can be used to control the
maximum neutron energy in the stream at the output of the source collimator.
There are serious contradictions in the theoretical and experimental data on the prompt fission neutron spectra for a number of fissile isotopes. Particularly large discrepancies are observed in the experimental data for the region of low (<0.5 MeV) and high (> 6 MeV) neutron energies. This is due to the large influence of systematic errors on the results of the neutron spectra measurements for these energy ranges, among which the main ones are the influence of the scattered neutrons and gamma-rays on the shape of the measured spectrum, the quality of n/γ separation, and the influence of the uncertainty in determining the time mark when the time-of-flight method used. The aim of this work was to create a universal digital spectrometer of the prompt fission neutrons. The spectrometer includes: the organic scintillator based on p-terphenyl for the fast neutron detection; slow neutron detector based on the inorganic scintillator Cs2YLiCl6:Ce, fission chamber. Using a digital approach to processing signals from different elements of the detector, it is possible to solve problems related to the suppression of background events and systematic errors in determining the occurrence time of the signals at a new qualitative level. The paper presents the results of test measurements in which a number of important characteristics of the spectrometer were determined - its detection efficiency, light output, quality of gamma-background suppression, time characteristics.
The possibility of control the maximum energy in the neutron flux by analyzing the pulse height spectra of the $^{10}$ B-detector [1] was investigated. Two possible nuclear reactions were considered: direct reaction and reaction throuh the exited $^{11}$B* nucleus with the production of $^{4}$He and $^{7}$Li. The ionization losses of nuclei in two detector gaps were calculated. A change in the ionization loss spectrum of the $^{4}$He, $^{7}$Li nuclei and their sum, depending on the neutron energy and the detection threshold in the second sensitive ionization gap of the $^{10}$B detector was found.
The measurements were performed at the output of the collimated channel of a compact neutron source based on the electron accelerator at several energies from 5 to 9 MeV. By increasing the detection threshold in the second gap of the detector, the signal of which served as the trigger, the contribution of events with the registration of the $^{4}$He nuclei can be suppressed in comparison with the contribution of the $^{7}$Li. The position of the maximum in the pulse height spectrum from the first gap of the detector and in the calculated spectra of ionization losses shifts with increasing of electron energy, the boundary energy of $\gamma$-quanta, and the maximum neutron energy. It is possible that this fact can be used to control the maximum neutron energy in the flux.
1.S.Potashev et al. // The 3rd Int. Conf. Part. Phys. Astr. (2018). KnE Energy & Physics. 2018. P. 115.
Under developing new position-sensitive ionization detector of fast neutrons with energies above 1 MeV events of $^{7}$Li and $^{4}$He nucleus emission from $^{10}$B layer is simulated. Detector gives possibility to determine direction of nucleus emission due to signals from anode and pairs of cathodes and grids. Ionization signals from detector gas gaps is proportional to the partial and total ionization losses of the nucleus. Nucleus is identified and its energy is determined by above magnitudes. Energy of incident neutron is calculated from reaction kinematics. Expected relative resolution of neutron energy is $\sim 6\%$. Choice of high signal threshold suppresses registration of $^{4}$He nucleus and other types of radiation and provides monotonic dependence of loss on $^{7}$Li nucleus energy. Detector efficiency in the energy range from $1$ to $7$ MeV varies slightly and is estimated as ~ $10^{-7}$ [1, 2]. Thus, it becomes possible to determine energy and coordinates of neutron without measuring the time of flight.
In [1], a laser plasma with electron temperature $\Theta_{e}$ ~ 1 keV and the lifetime of $\tau$ ≈ 0.5 ns was formed from rhenium metal containing ${}^{186m}$Re isomer nuclei ($T_{1/2}$ = 2×$10^{5}$ years) with an isomer concentration of ~ $10^{–3}$ %. In this plasma the stimulated de-excitation of ~ $10^{–5}$ % isomeric nuclei was observed. The experimental results made it possible to assume in the ${}^{186}$Re nucleus at an energy of a slightly higher isomer energy the existence of a previously unknown level to which a trigger transition occurs upon stimulation of de-excitation of the ${}^{186m}$Re isomer. Later this assumption was supported by the study of the decay curve of ${}^{186}$Re nuclei produced in the (p, n) reaction on ${}^{186}$W nuclei [2].
Only a weak effect was observed in [1], and for its amplification, a technique was proposed for the reactor production of the ${}^{186m}$Re isomer to a concentration of ~ 0.1 % and a technique for isolating the pure ${}^{186m}$Re isomer as a separate phase. Also instead of a laser plasma it was proposed to use a high-current electric discharge plasma, the lifetime of which increases to ~ 50 ns while maintaining the plasma temperature $\Theta_{e}$ ~ 1 keV [3].
To further enhance the stimulation effect, the irradiation of plasma, containing isomeric nuclei, by the photons resonant to the trigger transition was proposed [4], however, for this, it is first necessary to determine the energy of the trigger transition. In this work, the plasma itself is considered as a source of resonant irradiation when atoms with resonant characteristic X-ray radiation are introduced into it. With an increase in the lifetime of the discharge plasma and with resonant photon irradiation of ${}^{186m}$Re atoms, the probability of de-excitation of the ${}^{186m}$Re isomer in the plasma can be increased by four orders of magnitude compared to [1].
The results already give grounds for the development of a power unit based on the stimulated de-excitation of the ${}^{186m}$Re isomer with the following parameters: specific energy capacity ~ $10^{8}$ J/g, specific operating power ~ 1 kW/g, specific storage power ~ 70 $\mu$W/g.
At present the heavy ion accelerator complex NICA is under construction in Dubna, Russia. The Multi-Purpose Detectors (MPD) will operate at NICA to study the properties and phase diagram of strongly interacting matter. The Forward Hadron Calorimeter (FHCal) is one of the basic sub-detectors of MPD and is intended for the detection of the particles in very forward rapidity region, mainly, non-interacting projectile fragments (spectators). Since the FHCal has a beam hole, most of the bound spectators escape in this hole, while the free spectators (protons and neutrons) deposit their energy in calorimeter. Experimental study of energy and space distributions of the spectators could provide an important information about the geometry of the heavy-ion collisions, namely, the centrality and the reaction plane orientation. Also, the angular distributions of the spectators can carry the information about the transverse momentum obtained from the collision region.
In this report the simulation results of the energy and space distributions of spectators in FHCal are presented. The approaches for the measurements of the collision centrality and the reaction plane orientation are discussed. It would be shown that the measurement of the spectators with forward calorimeter has a spectrum of the important physical tasks.
This work was supported by the Russian Foundation of Basic Research (RFBR) Grant No. 18-02-40065.
Participating nucleons in collisions of relativistic nuclei are well separated kinematically from spectator nucleons, which propagate forward with the initial beam energy. In central $^{208}$Pb–$^{208}$Pb collisions (0-5% centrality) the nuclear centres are typically separated by less than 3.5 fm [1]. This suggests that only few nucleons in far nuclear periphery escape collisions and move forward as spectators. Indeed, as found by measurements with fixed targets at the CERN SPS [2], 9 neutrons, 7 protons and 0.5 deuterons are produced on average in central $^{208}$Pb–$^{208}$Pb collisions. The most central collisions can be unambiguously selected in experiments in colliders by requiring the highest multiplicity of secondary particles in the central barrel [3]. With our recently developed Abrasion-Ablation Monte Carlo for Colliders model (AAMCC) we calculate the yields of spectator neutrons and protons in central $^{197}$Au–$^{197}$Au and $^{208}$Pb–$^{208}$Pb collisions, respectively, at NICA and at the LHC. We demonstrate the sensitivity of the calculated yields to the presence of the neutron-skin [4] in initial nuclei and also evaluate the content of bound spectator nucleons in such collisions, which is extremely sensitive to the excitation energy of spectator matter. We argue that the measurements of central events with unequal numbers of spectator neutrons and protons (e.g., with a single proton accompanied by several neutrons and vice versa) can reveal these effects.
This work has been carried out with financial support of RFBR within the project 18-02-40035-mega.
References
To measure the centrality in heavy ion reactions in the future experiments CBM@FAIR, BM@N, NA61/SHINE@SPS and MPD@NICA the forward hadron calorimeters with transverse and longitudinal segmentations will be used. All these calorimeters have the beam hole in the center. This feature leads to uncertainty in determining the centrality, since in this case the total energy deposition in the calorimeter depends non-monotonically on the impact parameter. New approach using machine learning methods was developed to solve the problem of centrality determination by the calorimeters with the beam hole. This approach uses information about the spatial energy distribution of spectators in calorimeter. Details of this new approach for centrality determination and first results of applying the approach to the simulation data will be shown. This work was supported by the Russian Foundation of Basic Research (RFBR) Grants №18-02-40081 and №18-02-40065.
As the kinetic energy of nuclei grows, studying their fragmentation in collisions with fixed targets becomes an increasingly complicated task. Secondary spectator fragments emitted at small angles close to the beam do not allow the placement of advanced detectors for their registration. This explains the use of nuclear photoemulsion or track detectors at ~1–100 AGeV beam energies [1-3], where the universality of spectator fragmentation has been demonstrated [3]. It is impossible to detect spectator fragments in nucleus-nucleus collisions at RHIC and at the LHC. However, as shown in the present work, some features of the fragmentation at highest collision energies still can be deduced from forward neutrons and protons detected by Zero Degree Calorimeters [4]. We employ our Abrasion-Ablation Monte Carlo for Colliders model (AAMCC) to predict various correlations between the total charge of undetected nuclear spectator fragments $Z_{bound}$, their total mass Abound and the numbers of free forward neutrons and protons and describe measured dependencies [1-3]. AAMCC is based on the well-known Glauber Monte Carlo model [5] to calculate the numbers of participant and spectator nucleons and on the nuclear evaporation, Fermi Break-up and SMM models from Geant4 library [6] to simulate decays of exited spectator matter. The calculated correlations between the numbers of free spectator neutrons and Zbound are shown in Fig.1 for two collision energies. While the general shape of the correlation is preserved at the LHC, a higher yield of central events with small $Z_{bound}$ is predicted due to a larger $\sigma_{NN}$ in the caculations at the LHC.
In future LHC experiments $Z_{bound}$, $A_{bound}$ and the numbers of spectator neutrons and protons can be related to collision impact parameter which, in its turn, can be independently evaluated from the numbers of produced particles detected in the central barrel. We propose to evaluate $Z_{bound}$ along with $A_{bound}$ in each event by subtracting the measured numbers of free protons and neutrons from $Z$ and $A$ of initial nuclei corrected for estimated numbers of participants. In this way the studies of nuclear fragmentation can be extended to LHC energies in order to confirm or refute the universality of spectator fragmentation.
The work has been carried out with financial support of RFBR within the project 18-02-40035-mega.
References
The BM@N (Baryonic Mat