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The 20th International Conference on Strangeness in Quark Matter (SQM 2022) will focus on new experimental and theoretical developments on the role of strange and heavy-flavour quarks in high energy heavy-ion collisions and in astrophysical phenomena.
Scientific topics include:
This plenary talk presents an overview of recent ATLAS measurements related to heavy flavor quark production, modification, and collective motion in small and large collision systems, detailed studies of the collective behavior of bulk particles in large collision systems, and recent measurements in proton-lead, photon-nucleus, and proton-proton collisions aimed at addressing open questions about the underlying physics of small collision systems.
The second-order Fourier coefficients ($v_{2}$) of $\Upsilon$(1S) and J/$\psi$ mesons in high-multiplicity pPb collisions is studied using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy 8.16 TeV. The dimuons used to reconstruct the quarkonium states are coupled with charged hadrons using the long-range two-particle correlation technique. The measurement of the $\Upsilon$(1S) $v_{2}$ is reported for the first time in small collision systems. The results are discussed in terms of collectivity and modification of heavy quarks.
By using gravity/gauge correspondence, we employ an Einstein-Maxwell-Dilaton model to compute the equilibrium and out-of-equilibrium properties of a hot and baryon rich strongly coupled quark-gluon plasma. The family of 5-dimensional holographic black holes, which are constrained to mimic the lattice QCD equation of state at zero density, is used to investigate the temperature and baryon chemical potential dependence of the equation of state [1]. We also obtained the baryon charge transport coefficients, the bulk and shear viscosities as well as the drag force and langevin diffusion coefficients associated with heavy quark jet propagation and the jet quenching parameter of light quarks in the baryon dense plasma, with a particular focus on the behavior of these observables on top of the critical end point and the line of first order phase transition predicted by the model [2].
[1] Grefa, J., Noronha, J., Noronha-Hostler, J., Portillo, I., Ratti, C., Rougemont, R. 10.1103/PhysRevD.104.034002
[2] Grefa, J.,Hippert, M., Noronha, J., Noronha-Hostler, J., Portillo, I., Ratti, C., Rougemont, R. arXiv:2203.00139 [nucl-th]
To study the bulk properties of the quark-gluon-plasma (QGP) produced at the beam energy scan (BES) energies at the Relativistic Heavy Ion Collider (RHIC), we extend the (3+1)-dimensional viscous hydrodynamics CLVisc [1,2,3] to include net baryon number conservation and Israel-Stewart-like equation for baryon diffusion with the NEOS-BQS equation of state, fluctuating initial conditions from Monte-Carlo Glauber model, and the afterburner SMASH. This integrated framework is shown to provide a good description of identified particle spectra, mean transverse momenta and anisotropic flows for different centralities and over a wide range of collision energies (7.7-62.4 GeV). It is found that the mean momenta of identified particles and anisotropic flows increases mildly with the collision energy due to larger radial flow. We further compute the multiple-particle cumulant ratio v2{4}/v2{2} of elliptic flow across BES energies, and find that the relative fluctuations of elliptic flow are insensitive to the collision energy, consistent with the preliminary STAR data. Our model provides a benchmark for understanding the RHIC-BES data and studying the critical properties and phase structure of hot and dense QCD matter.
References:
[1] L.-G. Pang, H. Petersen, and X.-N. Wang, Phys. Rev. C97, 064918 (2018), arXiv:1802.04449
[2] L. Pang, Q. Wang, and X.-N. Wang, Phys. Rev. C86, 024911 (2012), arXiv:1205.5019.
[3] X.-Y. Wu, G.-Y. Qin, L.-G. Pang, and X.-N. Wang,(2021), arXiv:2107.04949
The production of quarkonia in hadronic collisions provides a unique testing ground for understanding quantum chromodynamics (QCD) since it involves both the perturbative and non-perturbative regimes of this theory. As the quarkonia formation is not yet fully understood, a variety of new experimental data serve as new insights and help to constrain the models. Additionally to the inclusive J/$\psi$ production, the ALICE detector can access both the physics of charmonium systems and beauty-quark production since the charmonium can be experimentally separated from the contribution from long-lived weak decays of beauty hadrons. Also, new experimental observables like the angular correlation between J/$\psi$ and charged particles bring new insights to quarkonium production in hadronic collisions. Measurements of the azimuthal correlation structure of emitted particles in high multiplicity proton-proton (pp) collisions can reflect the medium response to the initial collision geometry.
In this contribution, we present new results of the inclusive, prompt and non-prompt J/$\psi$ production in pp collisions at $\sqrt{s} = 5.02 $ and 13 TeV. The angular correlation between J/$\psi$ and charged particles in pp collisions at $\sqrt{s} = 13$ TeV will also be shown. Finally, the elliptic flow ($v_{2}$) of J/$\psi$ in high multiplicity pp collisions at $\sqrt{s} = 13$ TeV will be presented.
Quarkonia are excellent probes of deconfinement in heavy-ion collisions. For $J/\psi$, a bound state of $c\bar{c}$ quarks, the (re-)generation is found to be the dominant production mechanism at the LHC energies. On the other hand, the non-prompt component of $J/\psi$ production originating from b-hadron decays allows one to access the interaction of b-quarks with the QGP. Polarization and spin alignment measurements could also be used to investigate the characteristics of the formed medium. Different polarization for the $J/\psi$ in Pb–Pb as compared to pp could be related to the modification of the $J/\psi$ feed down fractions, due to the suppression of the excited states in the QGP, but also to the contribution of the regenerated $J/\psi$ in the low $p_\mathrm{T}$ region. Moreover, it has been hypothesized that quarkonium states could be polarized by the strong magnetic field, generated in the initial state of the collision, and by the large angular momentum of the medium in non-central heavy-ion collisions. In pp collisions, polarization measurements are useful tools to understand particle production mechanisms. In this talk, the measurements of the inclusive, prompt and non-prompt $J/\psi$ nuclear modification factor in Pb–Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02 \mathrm{TeV}$ and midrapidity will be shown. The determination of the non-prompt $J/\psi$ fraction extends down to very low $p_\mathrm{T}$ with a significantly improved precision compared to previous publications. The recently published results on the $J/\psi$ polarization with respect to the event-plane in Pb–Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02 \mathrm{TeV}$ and forward rapidity will be presented. The preliminary measurement of the $\psi$(1S) polarization in pp collisions at $\sqrt{s} = 13 \mathrm{TeV}$ as a function of the transverse momentum will also be discussed. Results will be compared with available calculations.
Because of the different binding energies, bottomonium mesons are particularly useful probes to understand the thermal properties of quark-gluon plasma. Previously, CMS observed the sequential suppression of $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S) in heavy ion (AA) collisions, which was widely accepted as evidence for the QGP formation. However, the $\Upsilon$(3S) yield was excessively low, thus allowing us to report only statistical upper limits. In this talk, we present a detailed study of the measurement of excited bottomonium states with improved analysis technique and high-statistics data that enables us to observe the $\Upsilon$(3S) meson in AA for the first time. The results are discussed together with the previous measurements in pPb collisions, which finally provides a full scan of all $\Upsilon$(nS) states over the whole phase space.
To understand the in-medium effects of quarkonia in heavy ion collisions, it is necessary to perform differential studies of various observables to have a global picture of the quarkonium dynamics in the quark-gluon plasma (QGP). Recent results in proton-proton collisions have suggested that J/$\psi$ mesons are produced with much more jet activity than model predictions, which indicate that the amount of isolated J/$\psi$ mesons with respect to the total production cross section plays an important role in interactions between charmonia and the QGP medium. In this presentation, we present the second-order and third-order Fourier coefficients, $v_{2}$ and $v_{3}$ for prompt and nonprompt J/$\psi$, and prompt $\psi(2S)$ mesons, with reporting the $v_{2}$ and $v_{3}$ for prompt $\psi(2S)$ mesons for the first time in heavy ion collisions. The results are discussed with theoretical calculations and discussed in terms of suppression and recombination effects. Also, we show the final results of the measurement of J/$\psi$-jets in pp and PbPb collisions. The jet fragmentation function of jets containing a J/$\psi$ meson is studied to probe the dependence of quenching effects on the degree of associated hadro-production inside the jet.
Charmonium production is a probe sensitive to deconfinement in nucleus-nucleus collisions. The production of J/$\psi$ via regeneration within the QGP or at the phase boundary has been identified as an important ingredient for the description of the observed centrality and $p_{T}$ dependence at the LHC. $\psi$(2S) production relative to J/$\psi$ is one possible discriminator between the two different regeneration scenarios. At RHIC and at the LHC, there is so far no significant observation of the $\psi$(2S) in nucleus-nucleus collisions in central events at low transverse momentum, where regeneration is the dominating process. The combined Run 2 data set of ALICE allows to extract a significant $\psi$(2S) signal in such a kinematic region at forward rapidity in the dimuon decay channel. In this contribution, we present for the first time results on the $\psi$(2S)-to-J/$\psi$ double ratio and the $\psi$(2S) nuclear modification factor in Pb-Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV, calculated with respect to a new pp reference with improved precision. Results are compared with model calculations.
Hydrodynamic expansion and jet quenching are responsible for the production of low and high transverse-momentum (𝑝𝑇) particle in heavy-ion collisions, respectively. However, it is still a challenge to simultaneously describe hadron nuclear modification factor $𝑅_{\rm 𝐴𝐴}$ and elliptic flow $𝑣_2$, especially in the intermediate $𝑝_𝑇$ region of 2$<𝑝_𝑇<10$ GeV/c. In this talk, we combine hydrodynamics, quark coalescence and jet quenching as well as the hadron cascade, and study their effects on hadron spectra and flow. We find the key to solving the $𝑅_{\rm 𝐴𝐴}$−$𝑣_2$ puzzle is the incorporation of quark coalescence into the state-of-the-art event-by-event simulations of heavy-ion collisions. Specifically, our new theoretical framework combines 1) the Coupled Linearized Boltzmann Transport and Hydrodynamic (CoLBT-Hydro) model, 2) a hadronization model including Cooper-Frye sampling, quark coalescence and string fragmentation, and 3) a hadron cascade model. For the first time, we can consistently describe and understand the experimental data on $𝑅_{\rm 𝐴𝐴}$and $𝑣_2$ along with their flavor dependence and hadron chemistry (proton-to-pion and kaon-to-pion ratios) from low to intermediate $𝑝_𝑇$ and high $𝑝_𝑇$ in heavy-ion collisions at both RHIC and LHC energies. Our prediction is an example of high-precision tests of the quark coalescence model in nuclear collisions.
Then I will talk about the quark number scaling of strange quark and light quarks in RHIC and LHC within the Cooper-Frye, quark coalescence and string fragmentation framework. We can simultaneously describe the different quark number scaling behaviors of strange quark and light quarks at RHIC and LHC . We expound that such different NCQ scaling behaviors at these two energies is associated with the different relative weights of quark coalescence and string fragmentation contributions at intermediate $p_T$ range and the strangeness enhancement in the bulk medium. This results can also be used to quantitatively test the quark coalescence model in the future.
[1] Wenbin Zhao, Weiyao Ke, Wei Chen, Tan Luo and Xin-Nian Wang, Phys. Rev. Lett. 128 (2022) no.2, 022302.
[2] Wenbin Zhao, Weiyao Ke, Wei Chen, Tan Luo and Xin-Nian Wang, in preparation.
[3] Wenbin Zhao, Che-Ming Ko, YuXin Liu, Guangyou Qin and Huichao Song, Phys. Rev. Lett. 125, 072301 (2020).
Femtoscopic correlations of identified and unidentified hadrons are measured with data recorded by the CMS experiment at the LHC over a broad multiplicity range and pair transverse momentum. The first femtoscopy measurements carried in CMS for all pair combinations of $\mathrm{K}^{0}_{\mathrm{S}}$, $\Lambda$ and $\overline{\Lambda}$ are reported. These identified particles are employed to perform $\mathrm{K}^{0}_{\mathrm{S}}\mathrm{K}^{0}_{\mathrm{S}}$, $\Lambda\overline{\Lambda}$ and $\mathrm{K}^{0}_{\mathrm{S}}\Lambda\oplus\mathrm{K}^{0}_{\mathrm{S}}\overline{\Lambda}$ femtoscopic correlations in pPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 8.16 TeV, and of $\Lambda\Lambda\oplus\overline{\Lambda}~\!\!\overline{\Lambda}$ in PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV, for the first time. The shape of the correlation function is observed to largely vary for different particle pair species, revealing the effect of the strong final state interaction in each case. Charged particle correlations measured in pp at $\sqrt{s} =$ 0.9, 2.76, 7 and 13 TeV, pPb at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV and peripheral PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 2.76 TeV with the CMS detector are shown in addition. The invariant radii results for $\mathrm{K}^{0}_{\mathrm{S}}\mathrm{K}^{0}_{\mathrm{S}}$ in pPb and PbPb collisions show similar behavior with multiplicity and pair transverse momentum as observed for charged hadrons in all colliding systems and energies. The strong interaction scattering parameters, scattering length and effective range, are extracted from $\Lambda\Lambda\oplus\overline{\Lambda}~\!\!\overline{\Lambda}$ and $\Lambda\overline{\Lambda}$ correlations using the Lednick\'y-Lyuboshits model for both pPb and PbPb collisions, and compared with other experimental and theoretical results.
We investigate extensions of the Hadron Resonance Gas (HRG) Model beyond the ideal case by incorporating both attractive and repulsive interactions into the model [1]. When considering additional states exceeding those measured with high confidence by the Particle Data Group, attractive corrections to the overall pressure in the HRG model are imposed. On the other hand, we also apply excluded-volume corrections, which ensure there is no overlap of baryons by turning on repulsive (anti)baryon-(anti)baryon interactions. We emphasize the complementary nature of these two extensions and identify combinations of conserved charge susceptibilities that allow us to constrain them separately. In particular, we find interesting ratios of susceptibilities that are sensitive to one correction and not the other. This allows us to constrain the excluded volume and particle spectrum effects separately. Analysis of the available lattice results suggests the presence of both the extra states in the baryon-strangeness sector and the repulsive baryonic interaction, with indications that hyperons have a smaller repulsive core than non-strange baryons. We note that these results are interesting for heavy-ion-collision systems at both the LHC and RHIC.
High-multiplicity proton-proton collisions at LHC show the onset of phenomena typical of heavy-ion collisions, such as collective effects, suppression of short-lived resonances, and strangeness enhancement. These effects, whose origin is still under debate, suggest a complex particle production mechanism whose relative contributions evolve smoothly going from low to high multiplicity collisions. Light-flavor hadrons are the most abundant particles produced in pp collisions and multi-differential measurements of their production yields play a key role in the study of the hadronization mechanism.
In this contribution, recent measurements of light-flavor hadron production as a function of the charged-particle multiplicity and the (unweighted) transverse spherocity in pp collisions are presented and discussed in the context of phenomenological models implemented in general-purpose Monte Carlo generators. These results are complemented by detailed measurements of the neutral pion, eta, and omega mesons in several multiplicity classes in pp collisions at $\sqrt{s}$ = 13 TeV up to an unprecedented high $p_{\rm T}$. These measurements allow a test of perturbative QCD calculations and represent an important baseline for heavy-ion studies. Finally, preliminary results that show the ALICE performance in measuring particle production using the newest 900 GeV pp data sample collected in October 2021 will also be presented.
Understanding light (anti-)nuclei production mechanism is a long-standing challenge in heavy-ion physics. Besides its own importance, it can benefit the search of QCD critical point as well as the detection of dark matter in space. In this presentation, we present a unified description of the microscopic dynamics of light (anti-)nuclei production in high-energy nuclear collisions by solving the relativistic kinetic equations with their nonlocal collision integrals treated with a stochastic method. The stochastic method is benchmarked in a box calculation, in which the thermal limits are correctly reproduced. Besides, our kinetic approach describes well the production of light clusters in both pp and heavy-ion collisions. The application of using light nuclei production to probe QCD critical point is further discussed
In recent years, ALICE has extensively studied the production of light (anti)(hyper)nuclei in different collision systems and center-of-mass energies. The production mechanism of light (hyper)nuclei is still under debate in the scientific community. Two classes of models are used to describe nuclear production: the statistical hadronisation model (SHM) and the coalescence model. In heavy-ion collisions, both models describe well the production yields of light nuclei and their ratios to the yields of hadrons, making it difficult to distinguish between the two. On the contrary, collision systems such as pp and p--Pb collisions are ideal to study the (hyper)nuclei production mechanism. In particular, in high multiplicity pp collisions, by combining the measurements of the production of (anti)nuclei and femtoscopic measurements, the coalescence parameters are compared with parameter-free coalescence predictions. In addition, by comparing the production of in-jet and out-of-jet (anti)deuterons, it is possible to observe an increase of the (anti)deuteron production probability in the jet as compared to that out of the jet. Additional information can be extracted from the study of very large and extremely loosely bound objects such as 3$\Lambda$H. This particle has a large wavefunction, hence its production yield in pp and p--Pb collisions is extremely sensitive to the nucleosynthesis models. With the precision of the presented production measurements, some configurations of the SHM and coalescence models can be excluded leading to tighter constraints to available theoretical ones.
Hadronic resonances having short lifetimes are very useful to study the hadron-gas phase that characterizes the late-stage evolution of high energy nuclear collisions. Indeed, regeneration and rescattering processes occurring in the hadron gas modify the measured yields of hadronic resonances and can be studied by measuring resonance yields as a function of system size and by comparing to model predictions with and without hadronic interactions. Measurements of the differential yields of resonances with different lifetime, mass, quark content, and quantum numbers help in understanding particle production mechanisms, lifetime of the hadronic phase, strangeness production, parton energy loss, rapidity yield asymmetry and collective effects. With its excellent tracking and particle identification capabilities, the ALICE experiment has measured a comprehensive set of both meson and baryon resonances. We present recent results on resonance production in pp, p-Pb, Xe-Xe and Pb-Pb collisions at various centre-of-mass energies, highlighting new results on $\Sigma$(1385) and $\Xi$(1820), thus extending to higher mass the study of baryonic resonances at the LHC. The obtained results are used to study the system-size and collision-energy evolution of transverse momentum spectra, yields, mean transverse momentum, yield ratios to stable hadrons, and nuclear modification factors. These results are compared to lower energy measurements and model calculations where available.
In this talk we will present recent results on light nuclei and hypernuclei production in heavy ion collisions over a wide beam energy range from the SIS18 to the LHC. Light clusters with mass number up to A=3 can be well described by a phase-space coalescence approach implemented in the microscopic transport model UrQMD. I will show that the final multiplicities for nuclear clusters in many experiments can be well described with this approach which assumes the formation of nuclei after kinetic freeze out and using only the two phase space separation parameters for deuterons and tritons. As expected for coalescence the coalescence parameters $B_2$ and $B_3$ scale with the appropriate power of the system volume for central collisions. Results for the centrality dependence of nuclei production will be presented. They show a breaking of this scaling for peripheral collisions. In addition, some special ratios will be discussed, like the $t*p/d^2$ or $_{\Lambda}^3H / ^3He * p/\Lambda$ ratio and how they depend on the beam energy. The possibilities of the creation of more exotic nuclei like those including a $\Xi$ or even charmed baryons will also be discussed.
This talk is based on:
[1] P. Hillmann, K. K\"afer, J. Steinheimer, V. Vovchenko and M. Bleicher,[arXiv:2109.05972 [hep-ph]], accepted for publication in Journ.Phys.G.
[2] S. Sombun, K. Tomuang, A. Limphirat, P. Hillmann, C. Herold, J. Steinheimer, Y. Yan and M. Bleicher, Phys. Rev. C 99, no.1, 014901 (2019).
[3] J. Steinheimer, A. Botvina and M. Bleicher, Phys. Rev. C 95, no.1, 014911 (2017).
Intriguing experimental results on two-particle azimuthal correlations in ultra-peripheral Pb+Pb collisions (UPCs) have been measured at the Large Hadron Collider (LHC) [1]. In this talk, I will present the first full (3+1)D dynamical simulations to study collective behavior in UPC events at RHIC and the LHC with the 3DGlauber+MUSIC+UrQMD framework [2, 3]. First, extrapolating from asymmetric p+Pb collisions, we explore whether a quasi-real photon $\gamma^*$ interacting with the lead nucleus in an ultra-peripheral collision can create a many-body system exhibiting fluid behavior. Assuming the strong final-state interactions, we provide model results for charged hadron multiplicity, identified particle mean transverse momenta, and charged hadron anisotropic flow coefficients and compare them with experimental data from the ALICE and ATLAS Collaborations. The elliptic flow hierarchy between p+Pb and $\gamma^*$+Pb collisions is dominated by the difference in longitudinal flow decorrelations and reproduces the experimental data well. Second, the net proton rapidity distributions in UPC events can provide crucial information about early-time baryon stopping dynamics because the projectile $\gamma^*$ does not carry baryon charges. I will show theoretical predictions for the net-proton rapidity distributions in UPC events at RHIC and LHC, which have potential discriminate power for the baryon junction model [4]. Our theoretical framework provides a quantitative tool to study particle production and collectivity for all system sizes, ranging from central heavy-ion collisions to small asymmetric collision systems at RHIC and LHC and even at the future Electron-Ion Collider.
[1] ATLAS Collaboration, Phys. Rev. C 104, 014903 (2021).
[2] Chun Shen and Björn Schenke, Phys. Rev. C 97, 024907 (2018).
[3] Wenbin Zhao, Chun Shen and Björn Schenke, [arXiv: 2203.06094].
[4] D. Kharzeev, Phys. Lett. B 378, (1996), 238-246.
Angular correlations present in dijet photoproduction are studied, for the first time, using ultraperipheral lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The second moment of the angular distribution, $\langle \cos(2\Phi) \rangle$, where $\Phi$ is the angle between the vector sum $\vec{Q}_\mathrm{T}$ and the vector difference $\vec{P}_\mathrm{T}$ of the transverse momentum vectors of the jets, is measured as a function of $\vec{Q}_\mathrm{T}$. This analysis amounts to the first, yet essential, step towards the extraction of the Wigner or Husimi gluon distributions, which are believed to be the most fundamental gluon distributions. It also introduces new techniques for the analysis of jet angular correlations in exclusive dijet events at colliders.
In this contribution, the similarity between small and large collision systems will be explored using the underlying event (UE) charged particle density, $N_{T}$, and the self-normalized observable based on transverse region multiplicity, $R_{T}$. A study of KNO-like scaling properties of the $N_{T}$ distributions in pp collisions at $\sqrt{s}$ = 2.76, 5.02, 7 and 13 TeV will be presented. Final measurements of charged particle production as a function of $N_{T}$ in pp, p–Pb and Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV will be presented in the toward, away and transverse regions. In addition, the UE contributions measured in the transverse region are subtracted from the toward and the away regions to search for jet-like modifications in small collision systems. The jet-like signals are studied both as a function of $N_{T}$ and of the leading particle transverse momentum. To explore the particle species dependence, the final results of $\pi$, K and p production as a function of $R_{T}$ in pp collisions at $\sqrt{s}$ = 13 TeV are presented. In addition, results on very forward energy, measured by the ALICE zero degree calorimeters (ZDCs), and differential studies of particle production will be presented for $\sqrt{s}$ = 13 TeV pp collisions and $\sqrt{s_{NN}}$ = 8.16 TeV p–Pb collisions. The event-activity based on UE measurements and very forward energy for pp collisions will be compared with p–Pb collisions. Finally, the results will be compared with the expectations of QCD-inspired Monte Carlo event generators, such as PYTHIA and EPOS-LHC, to test if these models can describe both the UE and the forward fragmentation observables, which are mainly driven by non-perturbative QCD physics.
We introduce a novel freeze-out procedure connecting the hydrodynamic evolution of a droplet of quark-gluon plasma (QGP) that has, as it expanded and cooled, passed close to a critical point on the QCD phase diagram with the subsequent kinetic description in terms of observable hadrons. The procedure converts out of equilibrium critical fluctuations described by extended hydrodynamics, known as Hydro+, into cumulants of hadron multiplicities that can be subsequently measured. We introduce a critical sigma field whose fluctuations cause correlations between observed hadrons due to the couplings of the sigma field to the hadrons. We match the QGP fluctuations obtained via solving the Hydro+ equations describing the evolution of critical fluctuations before freeze-out to the correlations of the sigma field. In turn, these are imprinted onto fluctuations in the multiplicities of hadrons, most importantly protons, after freeze-out via a generalization of the familiar half-a-century-old Cooper-Frye freeze-out prescription which we introduce. This framework allows us to study the effects of critical slowing down and the consequent deviation of the observable predictions from equilibrium expectations quantitatively. We can also quantify the suppression of cumulants due to the conservation of baryon number. We demonstrate the prescription in practice by freezing out the Hydro+ simulation in a simplified azimuthally symmetric and boost invariant background discussed previously.
Relativistic heavy-ion collisions can study properties of nuclear matter in high-energy experiments like the STAR experiment. One of the methods to learn about bulk matter is the femtoscopy technique, which relies on information carried by the particles produced during the collisions. The emission source parameters, like space-time characteristics, are provided using femtoscopic quantities. High statistics data from RHIC can made it possible to study the correlations between strange particles, like charged and neutral kaons. The pair-wise interactions between the identical kaons that form the basis for femtoscopy are quantum statistics and the Coulomb interaction for $K^{\pm}K^{\pm}$, and quantum statistics and the final-state interaction through the $f_0(980)/a_0(980)$ threshold resonances for $K^0_SK^0_S$. The interactions between non-identical kaons pairs of $K^0_SK^{\pm}$ are essential, as the strong FSI is described only by the $a_0(980)$ resonance, which could be a four-quark state.
This talk will present the femtoscopic measurements of strange particles with charged and neutral kaons correlations in Au+Au collisions at the RHIC energy. The experimental results will be compared with the theoretical predictions.
Heavy quarks are primarily produced via initial hard scatterings, and thus carry information about the early stages of the Quark-Gluon Plasma (QGP). Measurements of the azimuthal anisotropy of the final-state heavy flavor hadrons provide information about the initial collision geometry, its fluctuation, and more importantly, the mass dependence of energy loss in QGP. Due to the larger bottom quark mass as compared to the charm quark mass, separate measurements of charm and bottom hadron azimuthal anisotropy can shed new light on understanding the dependence of the heavy quark and medium interaction. Because of the high branching ratio and large $D^0$ mass, measurements of $D^0$ meson coming from $B$ hadron decay (nonprompt $D^0$) can cover a broad kinematic range and be a good proxy of the parent bottom hadrons results. In this talk we report both on the prompt $D^0$ and the first nonprompt $D^0$ measurements of the azimuthal anisotropy elliptic ($v_2$) and triangular ($v_3$) coefficients of nonprompt $D^0$ in PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV. The measurements are performed as functions of transverse momentum $p_\mathrm{T}$, in three centrality classes, from central to midcentral collisions.. Compared to the prompt $D^0$ results, the nonprompt $D^0$ $v_2$ flow coefficients are systematically lower but have a similar dependence on $p_\mathrm{T}$ and centrality. A non-zero $v_3$ coefficient of the nonprompt $D^0$ is observed. The obtained results are compared with theoretical predictions. The comparison could provide new constraints on the theoretical description of the interaction between heavy quarks and the medium.
The observation of collectivity signals in small hadronic collisions raises the question of whether the tiny droplet of quark-gluon plasma can form in small systems. Dynamics and hadronization of heavy flavor quarks in small-system collisions provide a powerful tool to address the origin of observed collective phenomena because of their early production time and sensitivity to the finite system size effect. In heavy-ion collisions, charm hadron production can occur via coalescence. One expects the effect to be more significant for baryons with three constituent quarks than mesons. Those motivate the studies of $\Lambda_c^+$ production in various collision systems.
In this talk, we report a comprehensive study of charm and bottom hadron elliptic flow in pp and pPb collisions with the LHC Run-2 data recorded by CMS, where a mass hierarchy is evident. We also present new measurements of the $\Lambda_c^{+}$ yields and ratios to prompt $D^0$ yields as functions of $p_\mathrm{T}$ and event multiplicity. They are directly compared with light flavor strange baryon-to-meson ratios to provide constraints on the charm hadronization in small systems. Moreover, ratios of $\Lambda_{c}^{+}$ over $D^{0}$ yields in pp and PbPb collisions, as well as the $\Lambda_c^+$ nuclear modification factors, will also be reported. We compare results from various collision systems to theoretical models. They provide crucial new insights into charm hadronization mechanisms and the possible QGP medium effects in high-multiplicity events.
Heavy quarks are one of the most important probes to study the properties of quark-gluon plasma (QGP). Hadronization of beauty quarks is not as well understood as in the charm sector. Illuminating the hadronization mechanism is crucial for extracting the transport properties of the QGP. We present new results on nuclear modification factors of $B^0_s$ and $B^+$ mesons and their yield ratios in pp and PbPb collisions at 5.02 TeV, using data recorded with the CMS detector in 2017 and 2018. The reported B-meson nuclear modification factors over an extended transverse momentum range will provide important information about the diffusion of beauty quarks and the flavor dependence of in-medium energy loss. The $B^0_s/ B^+$ yield ratio in pp and PbPb can shed new light on beauty hadronization mechanisms from small to large systems and on the relevance of parton recombination in the medium. We also report the first observation of the $B_{c}$ meson in nucleus-nucleus collisions, through partial reconstruction of the semi-leptonic decay $B_{c^{+}}$ $\rightarrow$ (J/$\psi$ $\rightarrow$ $\mu^{+}\mu^{-}$) $\mu^{+}$ $\nu_{\mu}$. Given the low production cross-section in proton-proton collisions, its production could be dramatically enhanced by the combination of beauty quarks with the charm quarks present in the plasma, providing additional insights into the recombination mechanism. The $B_{c}$ nuclear modification factors are compared with similar (CMS) measurements for other heavy-flavor mesons and quarkonia.
In this contribution the nuclear modification factor ($R_\mathrm{AA}$) of prompt charm hadrons and leptons from heavy-flavour hadrons decays measured in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV by the ALICE Collaboration are presented. The measurement of heavy-flavour leptons in Xe-Xe collisions is also discussed. Heavy quarks are a very suitable probe to investigate the quark-gluon plasma (QGP) produced in heavy-ion collisions, since they are mainly produced in hard-scattering processes and hence in shorter timescales compared to the QGP.
Measurements of charm-hadron production in nucleus-nucleus collisions are therefore useful to study the properties of the in-medium charm quark energy loss via the comparison with theoretical models. Moreover, the comparison of different colliding systems provide insights in the dependency on the collision geometry. Models describing the heavy-flavour transport and energy loss in an hydrodynamically expanding QGP require also a precise modelling of the in-medium hadronisation of heavy quarks, which is investigated via the measurement of prompt $\mathrm{D_s^+}$ mesons and $\Lambda_\mathrm{c}^{+}$ baryons. In addition, the measurement of the azimuthal anisotropy of strange and nonstrange D mesons is discussed. The second harmonic coefficient provides information about the degree of thermalisation of charm quarks in the medium, while the third one relates to its sensitivity to event-by-event fluctuations in the initial stage of the collision. A thorough systematic comparison of experimental measurements with phenomenological model calculations will be performed in order to disentangle different model contributions and provide important constraints to the charmquark diffusion coefficient $D_s$ in the QGP.
In this contribution, we present the latest measurements of $\mathrm{D}^0$, $\mathrm{D}^+$ and $\mathrm{D_s}^+$ mesons together with the final measurements of $\Lambda_\mathrm{c}^+$, $\Xi_\mathrm{c}^{0,+}$, $\Sigma_\mathrm{c}^{0,++}$, and the first measurement of $\Omega_\mathrm{c}^0$ baryons performed with the ALICE detector at midrapidity in pp collisions at $\sqrt{s}=5.02$ TeV and $\sqrt{s}=13$ TeV. Recent measurements of charm-baryon production at midrapidity in small systems show a baryon-to-meson ratio significantly higher than that in $\mathrm{e^+e^-}$ collisions, suggesting that the fragmentation of charm is not universal across different collision systems. Thus, measurements of charm-baryon production are crucial to study the charm quark hadronization in a partonic rich environment like the one produced in pp collisions at the LHC energies. Furthermore, the recent $\Lambda_\mathrm{c}^+/\mathrm{D}^0$ yield ratio, measured down to $p_\mathrm{T}=0$, and the new $\Xi_\mathrm{c}^{0,+}/\mathrm{D}^0$ yield ratio measured in p-Pb collisions will be discussed. The measurement of charm baryons in p-nucleus collisions provides important information about possible additional modification of hadronization mechanisms as well as on cold nuclear matter effects and on the possible presence of collective effects that could modify the production of heavy-flavour hadrons. Finally, the first measurements of charm fragmentation fractions and charm production cross-section at midrapidity per unit of rapidity will be shown for both pp and p-Pb collisions using all measured single charm ground state hadrons.
The production mechanism of light (anti)nuclei in heavy-ion collisions has been extensively studied experimentally and theoretically for many decades. Two competing (anti)nucleosynthesis models are typically used to describe light (anti)nuclei yields and their ratios to other hadrons in heavy-ion collisions: the statistical hadronization model (SHM) and the nucleon coalescence model. The possibility to distinguish these phenomenological models calls for new experimental observables. On a different front, given their large baryon number, light (anti)nuclei have a high sensitivity to the baryon chemical potential ($\mu_{\rm B}$) of the system created in the collision.
In this talk, the first measurement of event-by-event antideuteron number fluctuations in heavy-ion collisions is presented and compared with expectations of the SHM and coalescence model. In addition, the antinuclei-to-nuclei ratios are used to obtain a measurement of $\mu_{\rm B}$ in heavy-ion collisions with unprecedented precision.
The ratio of strange to non-strange hadron yields increases from low-multiplicity to high-multiplicity hadronic interactions, reaching values observed in heavy-ion collisions. The ALICE experiment investigates the microscopic origin of this striking phenomenon by performing dedicated multi-differential analyses in pp collisions at $\sqrt{s}$ = 13 TeV.
To separate strange hadrons produced in jets from those produced in soft processes, the angular correlation between high-$p_{\rm T}$ charged particles and strange hadrons is exploited. The near-side jet and out-of-jet yield of $K^{0}_{S}$ and $\Xi^{\pm}$ are studied as a function of the charged particle multiplicity, up to values comparable to those reached in peripheral Pb-Pb collisions.
In order to disentangle initial and final state effects, a new analysis exploits the concept of the effective energy available for particle production, which is anticorrelated with the forward energy deposited in the Zero Degree Calorimeters (ZDC). (Multi-)strange hadron production is studied as a function of the charged particle multiplicity measured at midrapidity and of the forward energy detected by the ZDC.
The results suggest that soft (i.e., out-of-jet) processes are the dominant contribution to strange particle production and provide new insights on the role of initial state effects on strangeness enhancement in pp collisions.
We will present model studies of dynamics of baryon number transport, strangeness conservation and their manifestation in $\Omega$-hadron correlations. Although strange quarks are produced in $s\bar{s}$ pairs, the ratio of $\Omega^{-}$ to ${\bar{\Omega}}^{+}$ is greater than one in heavy-ion collisions at RHIC. Thus the produced $\Omega$ hyperons must carry net baryon quantum numbers from the colliding nuclei. We will present results of $\Omega^{-}-K^{\pm}$, ${\bar{\Omega}}^{+}-K^{\pm}$, $\Omega^{-}-\bar{\Xi}$ and $\bar{\Omega}^{+}-\Xi$ correlations from model simulations of Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and 14.6 GeV. These correlations can probe dynamics for baryon number transport to mid-rapidities at these two beam energies. In addition, we use AMPT (default and string-melting modes) and UrQMD models to illustrate how hadronization schemes of quark coalescence and string fragmentations could leave imprints on such correlations. Implications on the experimental program to measure these correlations with the STAR experiment at RHIC will also be discussed.
We present a unique signal of jet-induced medium excitations: the enhancement of baryon-to-meson ratios around the quenched jets. To illustrate this, we study jet-particle correlations and the distributions of jet-induced identified particles with respect to the jet direction in Pb+Pb collisions at the LHC via a multi-phase transport model. We find a strong enhancement of baryon-to-meson ratios for associated particles at intermediate transverse momentum around the triggered jets in Pb+Pb collisions relative to p+p collisions, due to the coalescence of jet-excited medium partons. Since the lost energy from jets can diffuse to large angles, such baryon-to-meson-ratio enhancement is more pronounced for larger relative distance from the jet axis. We argue that the experimental confirmation of the enhancement of jet-induced baryon-to-meson ratios around the jets will provide an unambiguous evidence for the medium response to jet quenching in heavy-ion collisions.
Quantum Chromodynamics (QCD) predicts the existence of a deconfined state of matter called Quark-Gluon Plasma (QGP) at sufficiently high-temperature and/or high-energy density. In order to investigate the phase diagram of QCD matter, the first phase of the Beam Energy Scan (BES-I) program started at the Relativistic Heavy Ion Collider (RHIC) in the year 2010. In continuation of BES-I, a high statistics dataset from Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV was recorded by the STAR experiment at RHIC in the year 2017. The transverse momentum ($p_{T}$) spectra of identified hadrons are essential to study the bulk properties such as integrated yield (dN/dy), average transverse momenta ($\langle p_{T} \rangle$), particle ratios, and freeze-out parameters of the medium produced. The systematic study of bulk properties can shed light on the particle production mechanism in heavy-ion collisions.
In this talk, we will present the $p_{T}$-spectra of hadrons ($\pi^{\pm}$, $K^{\pm}$, p, and $\bar{p}$) at mid-rapidity ($|y|<$ 0.1) in Au+Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV. The centrality dependence of dN/dy, $\langle p_{T} \rangle$, particle ratios, chemical freeze-out and kinetic freeze-out parameters will also be presented and compared with the measurements at other beam energies.
The f$_0$(980) meson was observed several years ago in $\pi\pi$ scattering experiments. Despite a long history of experimental and theoretical studies, the nature of this short-lived resonance is far from being understood and there is no agreement about its quark structure. According to different models, it has been associated with $q\bar q$ structures, considered as a tetraquark, or as a $K\bar K$ molecule.
In this talk, the nature of the f$_0$(980) resonance is investigated exploiting the excellent tracking and particle identification of the ALICE experiment to measure the differential spectra and integrated yield of the f$_0$(980) meson produced in pp and p-Pb collisions at an energy of $\sqrt s$ = 5.02 TeV. The new results are discussed in the comparison with models and the properties of other hadrons. The nuclear modification factor shows hints of final-state effects in p-Pb collisions and will be presented and discussed in this perspective.
Recent multiplicity-dependent studies of particle production in pp and p-Pb collisions have shown similar features as in heavy-ion collisions. Measurements using resonances could help to understand the possible onset of collective-like phenomena and a non-zero lifetime of the hadronic phase in a small collision system. Measurements of the differential yields of resonances with different lifetimes, masses, quarks contents, and quantum numbers will provide information on the mechanisms that influence the shape of particle momentum spectra, the lifetime of the hadronic phase, strangeness production, parton energy loss, and collective effects. This talk presents new ALICE results on various hadronic resonances in small collision systems at LHC energies, including the multiplicity dependent measurements of $\Lambda$(1520) and charged K$^*$ and the production of $\phi$-meson pairs. The results will be compared with model calculations and measurements at lower energies.
Hypernuclei are bound states of nucleons and hyperons. The hyperon-nucleon ($Y$-$N$) interaction, an important ingredient for the nuclear equation-of-state (EoS), remains poorly constrained. Precise measurements of hypernucei intrinsic properties and production yields in heavy-ion collisions are crucial to the investigation of their production mechanisms and the strength of the $Y$-$N$ interaction. Model calculations predict that hypernuclei are abundantly produced at low energies due to high baryon density.
Thanks to the high statistical data taken from the STAR BES II program in 2018-2021, a series of measurements on production yields and properties of light hypernuclei at low energies are carried out. In this talk, the rapidity and energy dependence of light hypernuclei ($^{3}_{\Lambda}{\rm H}$, $^{4}_{\Lambda}{\rm H}$, $^{4}_{\Lambda}{\rm He}$) yields in Au+Au $\sqrt{s_{\rm NN}}=$ 3, 19.6, and 27 GeV collisions will be presented. The ratio of hypernuclei to light nuclei production yields will also be presented. We will also report precise lifetime measurements of light hypernuclei ($^{3}_{\Lambda}{\rm H}$, $^{4}_{\Lambda}{\rm H}$, $^{4}_{\Lambda}{\rm He}$) utilizing the BES datasets. The results will be compared with model calculations and physics implications will be discussed.
The production of short lived resonances like $K^{*0}$ provides a unique opportunity to probe the hadronic phase formed in heavy-ion collisions. Due to its short lifetime the decay daughters may interact with the medium which may lead to a change in the properties of the resonances. The decay particles may undergo rescattering and re-generation effects. Hence $K^{*0}/K$ provides a unique tool to investigate the interplay of re-scattering and regeneration effects in the hadronic phase of heavy-ion collisions. Recently STAR has completed the BES-II run resulting in high statistics Au+Au data with improved detectors and wider pseudorapidity coverage. This will help us to extend the measurement in both lower and higher $p_{T}$ range with less statistical uncertainty than that in BES-I.
We will report mass, width, and invariant yields of $K^{*0}$ using the 14.6 and 19.6 GeV BES-II data. The average transverse momentum of $K^{*0}$ will be shown and compared with other hadrons. The nuclear modification factor of $K^{*0}$ will be shown. The resonance to non-resonance ratio will be shown as a function of centrality to study the rescattering/regeneration effects. Measurement of the hadronic phase lifetime will be shown as a function of centrality and will be compared with other RHIC and LHC energies.
The production and interaction of light nuclei and hyper-nuclei in high-energy heavy-ion collisions have been a focus of theoretical and experimental interests for a long time. The production of light nuclei in heavy-ion collisions can be explained by the coalescence of produced or transported nucleons. Due to the low binding energies of light nuclei and hyper-nuclei, it is more likely that they are formed at later stages of the evolution of the fireball. Therefore, studying the collective flow of light nuclei and hyper-nuclei in the heavy-ion collisions can provide insights into their production mechanism. Further, the study of the collective flow of hyper-nuclei will shed light on the hyperon-nucleon (YN) interaction in dense nuclear medium.
In this talk, we will present the transverse momentum ($p_{T}$) and centrality dependence of elliptic flow ($v_2$) of $d$, $t$, and $^3\text{He}$ and their antiparticles in Au+Au collisions at $\sqrt{s_{NN}}$ = 14.6, 19.6, 27, and 54.4 GeV. $v_2(p_T)$ of light (anti-)nuclei will be compared with the AMPT+coalescence model. Mass number scaling of $v_2(p_T)$ of light (anti-)nuclei will also be shown. We will also report the first observation of the hyper-nuclei $^{3}_{\Lambda}$H and $^{4}_{\Lambda}$H directed flow ($v_1$) in $\sqrt{s_{NN}}$ = 3 GeV mid-central (5-40\%) Au+Au collisions in the fixed target mode.
Higher-order cumulants of net-proton distributions are sensitive to the details of the phase structure of the QCD phase diagram. Lattice QCD and QCD-based model calculations indicate that the signs of sixth and eighth order cumulants have different combinations in the hadronic phase, partonic phase, and near the transition temperature.
We report the first measurements of seventh and eighth order cumulants of net-proton distributions in the high statistics Au+Au collisions at $\sqrt{s_{NN}}$ = 27, 54.4, and 200 GeV. The measurements are performed at mid-rapidity $|y|<0.5$ within 0.4 $< p_{T} < 2.0$ GeV/$c$ using the Time Projection Chamber and Time-of-Flight detector. The measurements in Au+Au collisions at 200 GeV will be compared to those from Zr+Zr and Ru+Ru collisions to understand the system size dependence. The signs of the measured sixth, seventh, and eighth order cumulants will be contrasted to those expected from the lattice QCD and QCD-based models. The ratios of the measured cumulants will also be compared with those obtained from the transport and thermal models to understand the role of baryon number conservation and the validity of the models.
In heavy-ion collisions, the observation of the global and local polarization of hyperons has revealed the existence of large vorticities perpendicular to reaction plane due to systems’s orbital angular momentum and along beam direction due to collective velocity field, respectively. With the high-statistics data from isobar collisions of Ru+Ru and Zr+Zr at $\sqrt{s_{NN}}$ = 200 GeV collected by the STAR experiment, we present differential measurements of global polarization for $\Lambda/\bar{\Lambda}$ and $\Xi^{\pm}$ as a function of centrality, $p_T$, and $\eta$. These measurements allow us to study the possible magnetic field driven effects through the polarization difference between Ru+Ru and Zr+Zr, owing to a larger magnetic field in the former. Furthermore, the first measurements of $\Lambda$ hyperon local polarization along beam direction relative to the third order event plane as well as the second order event plane will be presented. A comparison of results from isobar and Au+Au collisions provides important new insights into the collision system size dependence of the vorticities in heavy-ion collisions.
Particle flow measurements, which provide evidence of the QGP medium, are a powerful tool to study the QGP evolution in heavy-ion collisions. Using the two-particle correlation technique, LHCb has observed the ridge structure due to particle flow, in the forward pseudorapidity range $2<\eta<5$ alongside the leading jet peak in long-range correlations ($|\eta|>2$). This talk will detail the analyses of the ridge structure and the extraction of flow harmonics in $p$Pb$ and PbPb collisions. This presentation will also include the details of new LHCb studies of Bose-Einstein Correlations with same-sign charged pions.
Elliptic flow coefficient, $v_2$, is sensitive to the dynamics at the early stages of the system evolution in heavy-ion collisions and equation of state of the medium.
Triangular flow $v_3$ is particularly sensitive to the initial geometry fluctuations.
The hadronic interaction cross sections of multi-strange hadrons and $\phi$ mesons are expected to be small. Hence, anisotropic flow of these hadrons provides information primarily from the early stages of the high energy collisions.
From the measurements based on the first phase of the RHIC beam energy scan (BES-I), number-of-constituent-quark (NCQ) scaled elliptic flow for $\phi$ mesons shows about 2 $\sigma$ deviations from other particles [1,2]. The apparent violation of NCQ scaling may indicate the dominance of hadronic interactions over partonic interactions at and below $\sqrt{s_{NN}}$ = 11.5 GeV. In this talk, with the enhanced statistics from the second phase of the RHIC beam energy scan (BES-II) program, we will present measurements with improved precision of $v_2$ and $v_3$ for $K^\pm$, $K_S^0$, $\phi$, $\Lambda$, $\bar{\Lambda}$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, and $\bar{\Omega}^{+}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 - 19.6 GeV from STAR. A test of the NCQ scaling of $v_2$ and $v_3$ will be revisited with high statistics data. Implications of these measurements in the context of QCD phase structure at high baryon density region will be discussed.
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[1]~L.~Adamczyk \textit{et al.} (STAR), Phys. Rev. Lett. \textbf{110}, 142301 (2013)
[2]~L.~Adamczyk \textit{et al.} (STAR), Phys. Rev. C \textbf{88}, 014902 (2013)
Global spin alignment is a preferential alignment of a particle’s spin along the orbital an6 gular momentum produced in heavy-ion collisions. The global spin alignment of vector mesons ($J^P$ = $1^−$) $\phi$ and $K^{\ast 0}$ may be sensitive to the vorticity and hadronization mechanism in the medium. The second phase of RHIC Beam Energy Scan (BES-II) program provides new and higher statistics data sets for Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7-19.6 GeV. From this data, we can make high precision measurements of $\phi$ and $K^{\ast 0}$ global spin alignment, allowing for more differential studies not possible with the BES-I data. We can also compare global spin alignment between $\phi$ and $K^{\ast 0}$, where the lifetime of $\phi$ is roughly ten times larger than that of $K^{\ast 0}$ and the latter is more sensitive to hadronic re-scattering. In this talk, we report high precision measurements for the global spin alignment of $\phi$ and $K^{\ast 0}$ at $\sqrt{s_{NN}}$ = 14.6 and 19.6 GeV from BES-II.
In this contribution, the final measurements of the centrality dependence of $R_{\rm AA}$ of non-prompt $\mathrm{D}^0$ and electrons from beauty hadron decays in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented. These measurements provide important constraints to the in-medium mass-dependent energy loss and hadronization of the beauty quark. The integrated non-prompt $\mathrm{D}^0$ $R_{\rm AA}$ will be presented for the first time and will be compared with the prompt $\mathrm{D}^0$ one. This comparison will shed light on possible different shadowing effects between charm and beauty quarks. In addition, the first measurements of non-prompt $\mathrm{D}_{s}$ production in central and semi-central Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be discussed. The non-prompt $\mathrm{D}_{s}$ measurements provide additional information on the production and hadronization of $\mathrm{B}_{s}$ mesons. Finally, the first measurement of non-prompt D-mesons elliptic flow in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will also be discussed. It will help to further investigate the degree of thermalization of beauty quark in the hot and dense QCD medium.
The early production of heavy-flavour partons makes them an excellent probe of the dynamical evolution of QCD systems. Jets tagged by the presence of a heavy-flavour hadron give access to the kinematics of the heavy partons, and along with correlation measurements involving heavy-flavour hadrons allow for comparisons of their production, propagation and fragmentation across different systems. The properties of heavy-flavour parton showers are driven by the large dead cone of heavy quarks, the presence of which is directly measured for the first time, using jets tagged with a fully reconstructed D$^{0}$ meson amongst their constituents, in pp collisions. Whilst traversing the QGP, these partons are expected to lose energy through interactions with the medium, at a different rate to their inclusive counterparts. To constrain the energy loss in the QGP, measurements of the nuclear modification factor of D$^{0}$ meson-tagged jets are presented in the $0-10\%$ most central Pb-Pb collisions. Properties of heavy-flavour jets are also investigated in small systems through measurements of the production and substructure of jets tagged with D$^{0}$ mesons or electrons originating from heavy-flavour decays. Measurements of the fragmentation function and radial shape of jets containing a $\Lambda^{+}_{c}$, probing different dimensions of the hadronisation dynamics of charmed baryons, are also presented in pp collisions. Additionally, measurements of D$^{0}$-hadron correlations and the correlation of electrons from heavy-flavour decays with hadrons are presented, in both pp and p-Pb collisions, probing the impact of cold nuclear effects and providing a baseline for future Pb-Pb measurements.
Quankonia are an important probe to study the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. In particular, the $J/\psi$ nuclear modification factor, $R_{AA}$, probes hot nuclear matter effects, such as the dissociation arising from the color screening effect and and the regeneration by deconfined charm and anti-charm quarks. On the other hand, the $J/\psi$ elliptic flow, $v_{2}$, provides information about the charm quark thermalization and $J/\psi$ regeneration. Measurements of $J/\psi$ $v_{2}$ and $R_{AA}$ together can provide a deep insight into the thermal and dynamical properties of the QGP. In 2018, the STAR isobar program (Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}} = 200$ GeV) collected the largest heavy-ion data sample so far, which provides a unique opportunity to study the $J/\psi$ production in these collisions with good precision. In this talk, we will present measurements of $J/\psi$ $v_{2}$ and $R_{AA}$ as a function of transverse momentum and centrality in Ru+Ru and Zr+Zr at $\sqrt{s_{NN}} = 200$ GeV.
We investigate the in-medium kinetics of the X(3872) and $B_c$ particles in ultra-relativistic heavy-ion collisions (URHICs). Our transport approach, previously employed for charmonia and bottomonia, is governed by two transport parameters: the equilibrium limit and inelastic reaction rate. The equilibrium limits of X(3872) and $B_c$ are entirely determined by the particles' masses and the charm-quark and bottom-quark fugacities as determined before. The reaction rate for the X(3872) is evaluated depending on its structure, being "large" for a DD molecule and "small" for a tetraquark (diquark-antidiquark). The reaction rate of the $B_c$ is calculated in the quasi-free approximation as used for charmonia and bottomonia. We assess the sensitivity of the final X(3872) yields and pT spectra on different scenarios for its width and initial conditions. We find that the final yields of the molecule structure are generally smaller than for the tetraquark, by around a factor of two, which is qualitatively different from calculations using instantaneous coalescence models. We also present the centrality and transverse-momentum dependence of the $B_c$ $R_{AA}$ and discuss it in the context of recent CMS experiment data.
This work has been supported by the U.S. National Science Foundation under grant no. PHY-1913286, and by the TAMU Cyclotron Institute's Research Development (CIRD) program.
The strong interaction among D mesons and light-flavor hadrons was completely out of experimental reach until recently. The scattering parameters governing elastic and inelastic D-pion/kaon/proton collisions are completely unknown. This poses strong limitations not only to the search of molecular states composed of charm and non-charm hadrons, but also to the study of the rescattering of charm mesons following their formation in ultrarelativistic heavy-ion collisions. In such collisions a colour-deconfined medium, quark-gluon plasma (QGP), is formed. The system experiences a
hydrodynamic expansion cooling down up to the chemical freeze-out, which is followed by a hadronic phase. The knowledge of the scattering parameters of charm hadrons with non-charm hadrons would be a crucial ingredient for models based on charm-quark transport in a hydrodynamically expanding QGP to describe the typical observables of heavy-ion collisions.
In this talk we will report on the first estimation of the scattering parameters governing the strong interaction of the D-proton channel measured by the ALICE Collaboration in high-multiplicity pp collision at s = 13 TeV at the LHC. The strong interaction is studied by means of correlation in momentum space and the analysis is extended to D-kaon and D-pion combinations. It is demonstrated that all the relevant scattering parameters for the interaction of D mesons with light-flavor hadrons will be experimentally determined thanks to the upgrades of the ALICE experimental apparatus planned for the LHC Run 4 and 5 data taking periods.
Strangeness production has been suggested as a sensitive probe to the early-time dynamics of the nuclear matter created in heavy-ion collisions. Transverse momentum distributions and yields of strange hadrons provide important information about the particle production mechanisms and help us to understand the properties of the created medium and its evolution in these collisions.
Thanks to the high statistical data taken from the STAR BES II program in 2018-2021, a series of measurements on production yields and properties of strangeness at low energies are carried out. In this talk, the productions of $K^0_S,~\phi,~\Lambda, ~\Xi^-$, and $\Omega^{-}$ from Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 3, 14.5, 19.6, and 27 GeV will be presented. The strange hadron spectra, rapidity density distributions, particle ratios, and nuclear modification factors will be reported. These results will be compared with those from higher collision energies and discussed within the framework of model calculations.
We study the $\phi$ meson production in heavy-ion collisions from
subthreshold energies of 1.23 A GeV up to RHIC energies within the
microscopic Parton-Hadron-String Dynamics (PHSD) transport approach where
the novel production channels of $\phi$ meson based on the coupled channel
$T$-matrix approach are implemented along with the collisional broadening
of $\phi$-meson spectral width in medium.
Since $\phi$ meson production is closely related to the production of kaon
and antikaon, antikaon properties are described via the self-consistent
coupled-channel unitarized scheme within a SU(3) chiral Lagrangian
($G$-matrix) which incorporates explicitly the $s-$ and
$p-$ waves of the kaon-nucleon interaction, and the in-medium modification
of kaons are accounted via the kaon-nuclear potential, which is assumed to
be proportional to the local baryon density.
The medium effects on the $\phi$ production is investigated by comparing
with the experimental data from the FOPI, HADES and STAR Collaborations.
The new production channels of $\phi$ meson as
well as the broadening of the width in medium enhances the $\phi$
production near threshold energies and we find agreement with data without
invoking unknown resonance decays, as done in alternative approaches.
Hadronization models are successfully describing the particle yields, particularly in high-energy nucleus-nucleus collisions [1]. They are also used to describe elementary processes, like pp interactions. Extensive measurements at $\sqrt{s}$= 17.3 GeV by NA49 and NA61/SHINE collaborations provided yields of numerous particles, including double-strange hyperons.
Reasonable description of all experimentally measured yields (including the enfant terrible of these models, the $\phi$ meson) was possible only when the canonical radius of volume containing strange particles was allowed to vary independently [2,3]. In this report, the extension of the hadronization model calculations within ThermalFist [4] using the new results obtained at lower energies by NA61/SHINE will be presented.
The $\overline{\rm K}$p system is characterised by the presence of several coupled channels, systems like $\overline{\rm K}^0$n and $\pi\Sigma$ with a similar mass and the same quantum numbers as the K$^{-}$p state. The strengths of these couplings to the K$^-$p system are of crucial importance for the understanding of the nature of the
$\Lambda$(1405) and of the attractive K$^-$p strong interaction.
In this talk, we will present the measurements of the K$^-$p and K$^0_s$p correlation function in relative momentum space obtained in pp collisions at $\sqrt{s}$ = 13 TeV, in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, and Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. The emitting source size varies between 1 and 2 fm for
pp, p-Pb and peripheral Pb-Pb, whereas for central Pb-Pb collisions it is between 5 and 9 fm. As the source size increases, the effect of the inelastic contributions is suppressed and the shape of the correlation function is mostly driven by the elastic interaction.
The strength and the effects of the $\overline{\rm K}^0$n and $\pi\Sigma$ inelastic channels on the measured K$^-$p correlation
function are investigated in the different colliding systems by comparing the data with state-of-the-art models of chiral potentials. Finally, a novel data-driven approach to determine the coupling weights, necessary to quantify the amount of produced inelastic channels in the correlation function, is presented. The comparison of chiral potentials to the measured K$^-$p interaction indicates that, while the $\pi\Sigma$-K$^-$p dynamics is well reproduced within the model, the coupling to the $\overline{\rm K}^0$n channel in the model is currently underestimated.
NA61/SHINE is a multipurpose fixed-target facility at the CERN Super Proton Synchrotron. The main goals of the NA61/SHINE strong interactions program are to discover the critical point of strongly interacting matter and study properties of the onset of deconfinement. To reach these goals, hadron production measurements are performed in the form of a two-dimensional scan by varying collision energy and system size. The Collaboration has recently finished data acquisition for its original program on strong interactions, accumulating broad data samples on hadron production in various systems in the SPS energy range.
In this contribution, the NA61/SHINE results on identified charged kaon and pion production in p+p, Be+Be and Ar+Sc collisions at SPS energy range ($\sqrt{s_{NN}}$=5.1-17.3 GeV) will be presented. The NA61/SHINE measurements of small and intermediate mass ion collisions establish an interesting system size dependence, showing a rapid change of hadron production properties that starts when moving from Be+Be to Ar+Sc system. In particular, Ar+Sc is the smallest system for which a significtheant enhancement of $K^+/\pi^+$ ratio with respect to p+p collisions is observed. Obtained energy and system size dependence of the measured charged hadron multiplicities will be compared with available world data and various theoretical models.
The Anomalous Viscous Fluid Dynamics model, AVFD, is used in concert with the charge-sensitive correlator $R_{\Psi_2}(\Delta S)$ to study the scaling properties of background- and chiral-magnetically-driven (CME) charge separation ($\Delta S$), characterized by the inverse variance $\mathrm{\sigma^{-2}_{R_{\Psi_2}}}$ of the $R_{\Psi_{2}}(\Delta S)$ distribution, in Au+Au, Ru+Ru, and Zr+Zr collisions at $\sqrt s_{\mathrm{NN}}=200$~GeV. The $\mathrm{\sigma^{-2}_{R_{\Psi_2}}}$ values for the background are event-shape-independent but show a characteristic scaling pattern with the charged-particle multiplicity, indicating an essential constraint for discerning background from the signal and a robust estimate of the difference between the backgrounds in Ru+Ru and Zr+Zr collisions. By contrast, the $\mathrm{\sigma^{-2}_{R_{\Psi_2}}}$ values for signal + background show scaling violations that characterize the CME-driven contributions. I will discuss these scaling patterns and their implication for the detection and characterization of the CME. Corrections to recent ${R_{\Psi_2}(\Delta S)}$ measurements that account for the background difference in Ru+Ru and Zr+Zr collisions will also be presented and discussed.
Recently, STAR reported the isobar (${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$, ${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) results for the chiral magnetic effect (CME) search [1]. The Ru+Ru to Zr+Zr ratio of the CME-sensitive observable $\Delta\gamma$, normalized by elliptic anisotropy ($v_{2}$), is observed to be close to the inverse multiplicity ($N$) ratio. In other words, the ratio of the $N\Delta\gamma/v_{2}$ observable is close to the naive background baseline of unity. However, nonflow correlations are expected to cause the baseline to deviate from unity. To further understand the isobar results, we study nonflow effects using the isobar data by studying two-particle correlations as functions of pseudorapidity and azimuthal angle differences ($\Delta\eta$, $\Delta\phi$) of the pairs. We fit this 2D distribution of same-sign pairs and attempt to extract the ``true'' $v_{2}$, whose difference from the measured $v_{2}$ is estimated as the nonflow contribution to the latter. We decompose the nonflow contributions to $N\Delta\gamma / v_{2}$ (isobar ratio) into three terms [2] and quantify each term by using the nonflow in $v_{2}$ measurement, published STAR data [1] and HIJNG simulations. From these estimates, we arrive at a new baseline of the isobar ratio of $N \Delta\gamma / v_{2}$ for the CME. We report this new baseline and discuss its implications.
[1] M. Abdallah et al. [STAR], Phys. Rev. C 105, no.1, 014901 (2022)
[2] Y. Feng, J. Zhao, H. Li, H. j. Xu and F. Wang, Phys. Rev. C 105, no.2, 024913 (2022)
Photon-photon and photonuclear reactions are induced by the strong electromagnetic field generated by ultra-relativistic heavy-ion collisions. These processes have been extensively studied in ultra-peripheral collisions with impact parameters larger than twice the nuclear radius. Since a few years, both the photoproduction of the J/ψ vector meson and the production of dileptons via photon-photon interactions have been observed in A–A collisions with nuclear overlap. Photoproduced quarkonia can probe the nuclear gluon distributions at low Bjorken-x, while the continuum dilepton production could be used to further map the electromagnetic fields produced in heavy-ion collisions and to study possible induced or final state effects in overlapping hadronic interactions. Both measurements are complementary to constrain the theory behind photon induced reactions in A–A collisions with nuclear overlap and the potential interaction of the measured probes with the formed and fast-expanding QGP medium. In this presentation, measurements of coherent J/ψ photoproduction cross-sections in Pb–Pb collisions in the 40%-90% centrality range, measured at midrapidity in the dielectron channel with ALICE will be presented for the first time using the full Run 2 data. Thanks to the excellent tracking resolution of the TPC, the transverse momentum distribution of coherently photoproduced J/ψ can be accurately measured. Final results on coherent J/ψ photoproduction cross-sections at forward rapidity in the dimuon decay channel in the 30-90% centrality range will also be shown. Finally, the measurement of an excess in the midrapidity dielectron yield at low mass and p$_{T}$, in the centrality interval 50-90% will be shown. Results will be compared with available models.
Electromagnetic probes such as photons and dielectrons are a unique tool to study the space-time evolution of the hot and dense matter created in ultra-relativistic heavy-ion collisions. They are produced by a variety of processes during all stages of the collision with negligible final-state interactions. At low dielectron invariant mass ($m_{\rm ee}$), thermal radiation from the hot hadron gas contributes to the dielectron spectrum via decays of $\rho$ mesons, whose spectral function is sensitive to chiral-symmetry restoration. At larger $m_{\rm ee}$, thermal radiation from the QGP carries information about the early temperature of the medium. It is nevertheless dominated by a large background of correlated heavy-flavour hadron decays affected by energy loss and flow in the medium. Alternatively, the transverse momentum ($p_{\rm T,ee}$) of virtual direct photons, including thermal photons at low $p_{\rm T,ee}$, can be extracted from the dielectron data together with inclusive photon measurements. In proton-proton (pp) collisions, such measurement serves as a fundamental test for perturbative QCD calculations and as a baseline for the studies in heavy-ion collisions. Recently, pp collisions with high charged-particle multiplicities have been found to exhibit interesting phenomena showing surprising similarities with those in heavy-ion collisions. Low-mass dielectrons could provide additional information regarding the underlying physics processes in such collisions.
In this talk, the latest ALICE results on dielectron studies in Pb-Pb and pp collisions at the center-of-mass energies of $\sqrt{s_{\rm NN}}$ = 5.02 TeV and 13 TeV will be presented using the large data sample collected during the LHC Run 2. The results will be compared to the expected dielectron yield from known hadronic sources and predictions for thermal radiation from the medium. The production of direct photons in the different colliding systems including high-multiplicity pp collisions will be discussed.
Drell-Yan process is considered as one of the essential probes to understand the initial state of the nucleons presented as the parton distribution function (PDF) for stand-alone nucleon and nuclear PDF (nPDF) for confined nucleon in the nucleus. In LHC era, Z and W boson productions in pPb and PbPb collisions have been used to investigate the initial state effects. In this presentation, we report the results of the Drell-Yan process in pPb collisions at a center of mass energy of 8.16 TeV with the CMS detector. The differential cross sections are presented versus dimuon $p_\mathrm{T}$, rapidity and $\phi^{*}$ in a wider dimuon mass region that includes not only the Z boson mass range but also the lower mass region down to 15 GeV. In addition, the forward-backward asymmetries are shown in both mass regions, where the uncertainties are found to be smaller than in model calculations. The results in the Z mass region are the most precise to date, while the measurements in the lower mass region allow access to a new phase space for nPDF studies with lower longitudinal momentum fraction $x$ and lower energy scale $Q^{2}$. All results are compared to EPPS16, and nCTEQ15WZ nPDFs, and the free-proton PDF CT14, to better understand the nuclear PDF and the sensitivity of the models in pPb collisions.
Strange and multi-strange hadrons have a small hadronic cross-section compared to light hadrons, making them an excellent probe for understanding the initial stages of relativistic heavy-ion collisions and QCD dynamics. Isobar collisions, $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr, at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV have been performed at RHIC. These collisions are considered to be an effective way to minimize the flow-driven background contribution to search for the possibly small CME signal. The deformation parameters are different between the two species and flow measurements are highly sensitive to it. Elliptic flow measurements for these collisions also give direct information about the initial state anisotropies. The collected datasets include approximately two billion events for each of the isobar species and provide a unique opportunity for statistics hungry measurements.
In this talk, we will present the elliptic flow ($v_{2}$) of $K_{s}^{0}$, $\Lambda$, $\bar{\Lambda}$, $\phi$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, and $\bar{\Omega}^{+}$ at mid-rapidity ($|y|<$ 1.0) for Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. The dependence of $v_{2}$ on centrality and transverse momentum ($p_{T}$) will be shown. The results will be compared with data from other collision systems like Cu+Cu, Au+Au, and U+U. The physics implications of such measurements in the context of nuclear deformation in isobars will be also discussed.
The interplay of the chiral anomaly and the strong magnetic field (~10$^{15}$ T) created in the off-central heavy-ion collisions could give rise to a collective excitation in the quark-gluon plasma called the Chiral Magnetic Wave (CMW), which can be experimentally sought by the charge asymmetry ($A_{\rm ch}$) dependence of elliptic flow $v_2$ of positively and negatively charged hadrons. However, non-CMW mechanisms such as local charge conservation (LCC) intertwined with collective flow can also lead
to a similar dependence of $v_2$ on $A_{\rm ch}$. The measurement with triangular flow ($v_3$) thus serves as a reference as it is not expected to be affected by the CMW.
In this talk, we present new ALICE measurements of $v_2$ and $v_3$ of inclusive and identified hadrons as functions of $A_{\rm ch}$ in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 and 5.02 TeV. The slope parameters of $\Delta v_2$-$A_{\rm ch}$ and $\Delta v_3$-$A_{\rm ch}$ correlations, where the $\Delta v_n$ are the differences between $v_n$ of positive and negative particles, are normalized and then compared with results from other experiments and models. In addition, the Event Shape Engineering (ESE) technique is adopted for the first time to quantitatively
distinguish the CMW signal and the LCC background. The upper limit of the CMW signal contribution is further extracted. Our measurements reveal that the background effect is dominant in the search for the CMW in heavy-ion collisions.
We discuss the QCD phase diagram in the presence of strong magnetic fields. It is known that the chiral symmetry is inevitably broken via the celebrated mechanism of the "magnetic catalysis"; the quarks confined in the cyclotron orbits are forced to form the chiral condensate due to the effective low dimensionality. In addition, we take into account the existence of heavy quarks as impurities embedded in the light-quark matter. Then, the dimensional reduction also inevitably gives rise to the formation of the heavy-light mixed quark condensate, leading to the "QCD Kondo effect" [1, 2].
Therefore, we discuss the competition between the “magnetic catalysis” and the “QCD Kondo effect” to determine the true ground state within the mean-field approximation [3]. We find a critical magnetic-field strength that defines the phase boundary. While the Kondo condensate is excluded in the lower strength, a coexistence phase is realized in the higher strength. The growth of the Kondo condensate makes the chiral condensate saturate to a constant magnitude in the coexistence phase.
[1] K. Hattori, K. Itakura, S. Osaki, and S. Yasui,Phys.Rev.D 92 (2015) 065003 [1504.07619 [hep-ph]]
[2] S. Ozaki, K. Itakura, and Y. Kuramoto, Phys.Rev.D 94 (2016) 074013 [1509.06966 [hep-ph]]
[3] K. Hattori, D. Suenaga, K. Suzuki, S. Yasui, In preparation.
The Electron-Ion Collider is a future collider planned to be built at BNL in about 2030. It will provide physicists with high luminosity and highly polarized beams of electrons, protons, and ions with a wide range of nuclei species at different collision energies, covering an extensive kinematic range. The EIC physical goals include measuring the generalized parton distribution from Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) experiments, performing precision 3D imaging of the nuclei structure, studying color confinement and hadronization mechanisms, and understanding the spin structure of the proton. In order for the EIC to achieve its physics goals, a high-resolution electromagnetic calorimeter (EMCAL) is required to measure electrons and photons and to achieve good particle identification. We propose two design options for EIC EMCALs. The first technique is to improve the resolution tungsten/scintillating fiber (W/SciFi) EMCAL being built for sPHENIX with new technologies. The other possibility is to develop tungsten/shashlik (W/shashlik) EMCAL with a highly segmented readout configuration to achieve better energy and position resolution. In this work, we carry our our studies on EIC EMCAL designs using GEANT 4 simulations. We will first present the general performance of the sPHENIX W/SciFi and shashlik EMCALs. In addition, we study fully reconstructed $\pi^0 \to \gamma\gamma$ from EIC endcap EMCALs in the hadron-going direction. The $\pi^0$ merging probability a function of $\pi^0$ energy with different EMCAL tower designs and light collection efficiency maps of the shashlik towers modeled by TracePro software will be reported. We will also present various designs, general performance, and $\pi^0\to \gamma\gamma$ merging probability simulation studies for the forward EMCAL in ECCE, which has been approved by the United States Department of Energy and National Academy of Science to be the detector 1 for the EIC.
The high luminosity LHC, or HL-LHC provides the opportunity to study heavy ion, proton-nucleus, photon-nucleus and photon-photon collisions with unprecedented luminosities. The LHC heavy ion community has mapped out a large range of physics measurements at the HL-LHC that will push forward our understanding of both QCD, QED and even electroweak physics. The measurement of forward neutrons and photons in Zero Degree Calorimeters, or ZDCs, is essential for event classification and triggering. In order to reach the required luminosities, the LHC interaction regions will be completely remodeled, necessitating the need to build new ZDCs that are both thinner and much more radiation hard. This challenge motivated the formation of a joint project between ATLAS and CMS to build new ZDCs for Run 4. The ZDCs are based on very radiation hard fused silica rods that produce Cherenkov light. These rods have been developed in collaboration with the LHC BRAN group and private companies. The Run 4 ZDCs are the first joint detector project between CMS and ATLAS. This talk will present the capabilities of the new ZDCs and recent test beam analysis.
Recent experimental measurements display an enhanced production of charmed baryons in high-energy nucleus-nucleus collisions. Quite surprisingly the same is found in proton-proton collisions, in which the relative yields of charmed baryons do not agree with the expectations based on e+e- collisions and with the predictions of those QCD event generators in which the hadronization stage is tuned to reproduce this more elementary situation.
Medium modification of hadronization, via some mechanism of recombination with light thermal partons, has been known for long to be an essential ingredient to implement in transport calculations in order to describe experimental data of heavy-flavour production in nucleus-nucleus collisions. This is true both for the momentum and angular distributions of the final charmed/beauty hadrons and for their relative yields.
In this talk I will present the main features of a novel hadronization scheme we developed and implemented in our POWLANG transport setup, showing also our first results for the heavy-flavour particle ratios and flow coefficients in nucleus-nucleus collisions, in satisfactory agreement with recent experimental data. The model is based on the formation of color-singlet clusters via recombination of a charm quark with a light thermal antiquark or diquark (assumed to be present in the medium around the critical temperature) from the same fluid cell. If the cluster is sufficiently light it undergoes a two-body decay, if its invariant mass is larger it is treated as a Lund string and accordingly fragmented. The model has some nice features: modelling hadronization as a 2->N process allows exact four-momentum conservation; involving particles from the same fluid-cell it contains by construction space-momentum correlations; recombination with diquarks allows one to describe charmed-baryon production; at large pT it naturally approaches standard vacuum-like fragmentation.
Results referring to nucleus-nucleus collisions can be found in our recent publication 2202.08732 [hep-ph].
A consistent modelling of the proton-proton reference, with the assumption of the formation of a small short-lived QGP droplet, in medium heavy-quark transport and hadronization is currently under development and preliminary results will be shown.
Ultra-relativistic heavy ion collisions are expected to generate a huge electromagnetic (e.m.) field that is envisaged to induce several effects on hot QCD matter including the possibility of local parity and local parity and charge conjugation symmetry violations. A direct signature of such e.m. fields and a first quantitative measurement of its strength and lifetime are still missing.
We will discuss why it is expected to generate a splitting of the directed flow of charged particles and anti-particles, which allow to constraint the e.m. field and can be considered also as a possible probe of the formation of the quark-gluon plasma phase. Moreover, we have found a general formula for all possible charge dependent flow observables that can be generated by the strong electromagnetic fields in non-central relativistic heavy ion collisions. The formula has a very simple form at pT larger than several GeV/c, which can be treated as the signature of charged dependent flow observables induced by e.m. fields. Furthermore, we found that the v1 splitting depends critically on the time evolution of the magnetic field. Based on this study, we finally discuss why the measurement of leptons from Z0 decay and its correlation to the charmed mesons are better in probing e.m. fields and thus opening a new way to constrain the EM field.
The second topic we want to discuss is the modification of the Z0 leptonic invariant mass in the presence of EM fields. We found that EM fields will decrease the Z0 leptonic invariant mass and increase the width of it by few hundred MeV if the large of D0 and anti-D0 measured by ALICE is all due to EM fields. Moreover, both the invariant mass and its width are found to approximately depend on the integral of magnetic field quadratically. This provides an independent way to constrain the EM field.
[1] Y. Sun, V. Greco and X.N. Wang, Phys. Lett. B 827, 136962 (2022).
[2] Y. Sun, S. Plumari and V. Greco, Phys. Lett. B 816, 136271 (2021).
[3] Y. Sun, V. Greco and S. Plumari, Eur. Phys. J. Plus 136, 726 (2021).
[4] S. K. Das, S. Plumari, S. Chatterjee, J. Alam, F. Scardina and V. Greco, Phys. Lett. B 768, 260-264 (2017).
The theoretical analysis of experimental observations, such as the mass hierarchy effect, often neglects some ingredients, which may be proven to have a significant impact. The forthcoming measurements at RHIC and LHC will generate heavy flavor data with unprecedented precision, providing an opportunity to utilize high-pT heavy flavor data to analyze the interaction mechanisms in the quark-gluon plasma. To this end, we use our recently developed DREENA framework based on the dynamical energy loss formalism. We present [1]: i) How to disentangle the signature of different interaction mechanisms (i.e., radiative and collisional energy losses) at the same dataset. ii) Novel observables susceptible to these different mechanisms to be tested by future high-precision measurements. iii) Analytical and numerical extraction of the mass hierarchy/dead cone effect in energy losses through this observable.
[1] Bojana Ilic and Magdalena Djordjevic, arXiv:2203.06646 [hep-ph]
Ultraperipheral lead-lead collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV produce very large photon fluxes that fundamental quantum-mechanical processes can be observed and well studied. Measurements of tau lepton pair in ultraperipheral PbPb collisions with data collected by CMS during the LHC Run 2 will be presented for the first time. The measurement paves the way for the determination of the anomalous magnetic moment of the tau lepton, currently poorly constrained.
The exclusive photoproduction of vector mesons provides a unique opportunity to constrain the gluon distribution function within protons and nuclei. Measuring vector mesons of various masses over a wide range of rapidity and as a function of transverse momentum provides important information on the evolution of the gluon distribution within nuclei. A variety of measurements, including the exclusive J/$\psi$, $\rho$, and $\Upsilon$ meson production in pPb (at nucleon-nucleon center of mass energies of 5.02 and 8.16 TeV) and PbPb (5.02 TeV) collisions, will be presented as a function of squared transverse momentum and the photon-proton center of mass energy. Finally, compilations of these data and previous measurements are compared to various theoretical predictions.
Electroweak W and Z bosons created in hard-scattering processes at the early stage of the collisions are efficient probes of the initial state of the collisions. While the measurements of W and Z bosons in p–Pb and Pb–Pb collisions provide insights on the nuclear modification of the parton distribution functions, the results in pp collisions are a stringent test of perturbative QCD-based calculations and production mechanisms. In pp collisions, W bosons can be produced by pair annihilation but also by higher order processes with additional hadron production. An investigation of these bosons, in relation to the hadrons in the rest of the event, can give insight into multi-parton interactions in high-multiplicity events and the role of color-reconnection mechanisms. Electroweak bosons are studied with ALICE in pp collisions at $\sqrt{s}$ = 13 TeV, p–Pb collisions at $\sqrt{s_{NN}}$ = 8.16 TeV and Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV via their leptonic decays in the muon and electron channels at forward rapidity (−4 < η < −2.5) and midrapidity (|η| < 0.8), respectively. The observations in p–Pb and Pb–Pb collisions at forward rapidity give access to low Bjorken-x values, a phase-space region poorly constrain by heavy-ion experiments.
A review of the most recent results on the production of W+, W− and Z bosons is presented. The results include differential measurements of the normalised production yields, production cross sections and nuclear modification factors as a function of rapidity, transverse momentum, collision centrality and charged-particle multiplicity. The lepton-charge asymmetry measurement is also reported. A particular emphasis will be placed on the new measurement of the production of W bosons in association with hadrons as a function of the charged-particle multiplicity in pp collisions. Comparisons with theoretical model calculations, providing insights on production mechanisms and new constraints for the determination of the nuclear parton distributions functions will also be discussed.
For several years there has been a strong interest in measuring collective effects in small systems such as proton-proton (pp) and proton-lead (pPb). Such measurements give new insights into the nature of QCD and the meaning of collectivity. In recent years ALEPH, ATLAS, and ZEUS collaborations have extended these studies to electromagnetic interactions such as electron-positron (ee), photon-lead ($\gamma$Pb), and electron-proton (ep) systems, respectively. No evidence of collectivity as in pp or pPb (for the same degree of collectivity) was found, placing a bound on the multiplicity range of long-range collectivity. The CMS Collaboration further extends the measurements into photon-proton ($\gamma$p) and pomeron-lead (I$\!$PPb) interactions using ultraperipheral pPb collisions at 8.16 TeV. Such interactions provide unique initial conditions with event multiplicity lower than in pp and pPb systems but comparable with ee and ep systems, whereas, and in contrast to the other systems, I$\!$PPb is a pure QCD interaction. This talk will summarize the first measurements of long-range particle correlations in $\gamma$p and I$\!$PPb systems.
Hydrodynamics has been quite successful in explaining observables of heavy ion collisions especially in low transverse momentum regime across varied collision systems. Recently hydrodynamics has also been used satisfactorily to explain proton-proton collision. This has been puzzling and has led to the discussion about the smallest volume for which hydrodynamics can be applied. The meaning of hydrodynamics itself has been under scrutiny with non-requirement of local equilibrium or pressure isotropy for its applicability. The second order viscous hydrodynamics, requires a transport coefficient called relaxation time, to maintain casualty. This relaxation time acts as a regulator for non-hydro modes of the complete hydrodynamic evolution. In phenomenological studies this relaxation time has been taken as to be a constant and much attention has gone into fixing shear viscosity to entropy density ratio. But this regulator also serves as a tool to gauge the role of non-hydro modes especially in peripheral heavy ion collisions and small systems. In the present study, we analyze the effect of different relaxation times on elliptic flow of light mesons, for PbPb and AuAu collision systems with optical Glauber and IPGlasma initial conditions of hydrodynamics. We hence study sensitivity of non-hydro modes by varying relaxation time for different systems of collisions and energies.
Dielectrons are an exceptional tool to dissect the evolution of the medium created in heavy-ion collisions. In central collisions, the energy densities are sufficient to create a quark-gluon plasma (QGP). Thermal $e^+e^-$ pairs with invariant mass around $1.5 \mathrm{GeV}/c^2$ can be used to estimate the temperature of the QGP.
At LHC energies, the cross section of heavy-flavour (HF) production is large and correlated HF hadron decays dominate the dielectron yield for invariant masses above $1.1 \mathrm{GeV}/c^2$. Their contribution is modified in the medium compared to elementary collisions to an unknown extent, leading to large uncertainties in the subtraction of known hadronic sources. Therefore, a topological separation based on the distance-of-closest approach ($DCA$) to the primary vertex is a promising alternative approach. The proper decay length of HF hadrons is of the order of $c\tau\approx 100-500 \mu\mathrm{m}$, hence their reconstructed decay electrons do not point to the primary vertex of the collision. This allows to disentangle them from the prompt contribution of thermal dielectrons.
In this poster, first preliminary results on the $DCA_{ee}$ spectra of dielectrons produced in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02 \mathrm{TeV}$ with ALICE will be presented. The measurements are compared to reference distributions from simulations and expectations from theory. Finally, a first attempt to extract a prompt thermal contribution in the intermediate mass region is performed by fitting the measured $DCA_{ee}$ spectrum.
We consider the probability of thermal production of uuddss states with small radii $r=01-0.4$ fm and small masses $m<2$ GeV in Pb+Pb collisions at \sqrt(s)=2.76 TeV. We use thermal model which was tuned to AGS, RHIC, LHC data and predicts $T=150-170$ MeV.
Hereby we compare the production rates for Sexaquarks with different masses and different radii.
We found that sexaquarks are produced with relatively high rates for both 0 and 0.4 fm radii and for masses of 1700 and 1960 MeV.
We estimate ratios of Sexaquarks uuddss to hadrons (protons, kaons, Lambda) and deutrons in Pb+Pb collisions at LHC.
At T=170 MeV the ratio of thermal Sexaquark with mass 1960 MeV to thermal deutron is about 0.45.
In this contribution, we present for the first time a scenario according to which early quark deconfinement in compact stars is triggered by the Bose-Einstein condensation (BEC) of a light sexaquark (S) with a mass $m_S<2054$ MeV, that has been suggested as a candidate particle to explain the baryonic dark matter in the Universe. The onset of S BEC marks the maximum mass of hadronic neutron stars and it occurs when the condition for the baryon chemical potential $μ_B=m_S/2$ is fulfilled in the center of the star, corresponding to $M_{onset}\le 0.7 M_\odot$. In the gravitational field of the star the density of the BEC of the S increases until a new state of the matter is attained, where each of the S-states got dissociated into a triplet of color-flavor-locked (CFL) diquark states. These diquarks are the Cooper pairs in the color superconducting CFL phase of quark matter, so that the developed scenario corresponds to a Bose-Einstein condensation - Bardeen-Cooper-Schrieffer (BEC-BCS) transition in strongly interacting matter. For the description of the CFL phase, we develop here for the first time the three-flavor extension of the density-functional formulation of a chirally symmetric Lagrangian model of quark matter where confining properties are encoded in a divergence of the scalar self-energy at low densities and temperatures.
Fluid dynamical modelling of heavy-ion collisions at RHIC BES, as well as at future FAIR and NICA energies, has its own challenges as compared to classical top RHIC or LHC studies. One of them is due to the long inter-penetration phase of the incoming nuclei, which results in a complex geometry of the initial state. Conventional hydrodynamic models, where fluid phase starts at a fixed proper time $\tau_0$, therefore miss a part of the compression stage of collision and may be therefore less sensitive to the EoS of the medium. Multi-fluid dynamics addresses the above challenge with a phenomenological albeit self-consistent way, where the incoming nuclei are modelled as droplets of cold nuclear fluid.
We present a multi-fluid dynamic approach 3FH-NG to simulate heavy-ion collisions at RHIC BES, reimplemented from scratch using 3+1 dimensional relativistic viscous hydro code vHLLE. We discuss the challenges in constructing the approach and present benchmark calculations for Au-Au collisions at different RHIC BES energies.
One important challenge in our field is to understand the initial condition of the QGP and constrain it using sensitive experimental observables. Recent studies show that the Pearson Correlation Coefficient (PCC) between vn and event-wise mean transverse momentum [pT], rho(vn, [pT]), and its centrality dependence can probe several ingredients of the initial state, such as number and size of sources, nuclear deformation, volume fluctuation, and initial momentum anisotropy. In particular, a recent calculation shows that the 129Xe nucleus is triaxially deformed, which is expected to enhance rho in 129Xe+129Xe relative to 208Pb+208Pb collisions. This talk presents comprehensive and precision measurements of vn-pT correlation in 129Xe+129Xe and 208Pb+208Pb collisions for harmonics n = 2, 3, and 4. The results are obtained via the standard and subevents cumulant methods to assess the role of non-flow and flow decorrelations in these observables, and they are found to be small in the mid-central and central collisions in these systems. All PCC coefficients, rho_2, rho_3 and rho_4 show rich and non- monotonic dependence on centrality, pT and eta, reflecting the fact that different ingredients of the initial state impact different regions of the phase space. For example, we found the result depends on the centrality estimator used in the analysis, indicating a strong influence of volume fluctuations. On the other hand, the ratio of 𝜌# between the two systems is less sensitive to the centrality estimator, and in the ultra-central region, the value of the ratio suggests that 129Xe has large quadrupole deformation but with a significant triaxiality. All current models fail to describe many of the observed trends in the data, pointing to the unprecedented constraining power enabled by this precision measurement.
The effect of deformation in nuclear geometry on both initial and final state observables has been reported by recent theoretical developments as well as experimental studies. However, in addition to fixed nuclear deformation, the nuclear geometry can manifest "Shape Coexistence" as evident from low-energy spectroscopic measurements. This study aims to quantify the effects of shape coexistence in heavy- collisions using the Glauber model. The effect of shape coexistence on the initial state observables such as eccentricity and area fluctuations are reported in this work.
We present a systematic study of $\Lambda$ hyperon polarization in heavy-ion collisions at HADES energies within the framework of microscopic transport model UrQMD combined with the hadron-resonance gas statistical model. This study demands a complex analysis of the fireball evolution including time slices, extraction of temperature and chemical potentials, as well as freeze-out conditions of Λ hyperons and study of the formation and space-time evolution of thermal vorticity. Two systems and four impact parameters are considered: Au+Au at $\sqrt{s_{NN}} = 2.42$ GeV and Ag+Ag at $\sqrt{s_{NN}} = 2.55$ GeV with $ b=3.0,5.5,7.5,9.0$ fm. Rapidity and transverse momentum dependence of the polarization are obtained and show a good agreement with preliminary experimental data as well as centrality and energy dependence of global polarization.
In high-energy heavy-ion collisions, the energy density profile of the produced quark-gluon plasma and its space-time dynamics are sensitive to the shape and radial profiles of the nuclei, described by the collective nuclear structure parameters including quadrupole deformation $\beta_2$, octupole deformation $\beta_3$, radius $R_0$ and surface diffuseness $a$ [1-3]. Using AMPT simulations as a proxy for hydrodynamics, we find a general scaling relation between these parameters and a large class of experimental observables such as anisotropic flow $v_n$, particle multiplicity distribution $p(N_\mathrm{ch})$ and mean transverse momentum $[p_T]$ fluctuations. In particular, we show that the ratio of these observables between two isobar collision systems depends only on the differences of these parameters. Using this scaling relation, we show how the nuclear structure parameters of $^{96}$Ru and $^{96}$Zr conspire to produce the non-monotonic centrality dependence of ratios of $v_n$, $p(N_\mathrm{ch})$ and mean $[p_T]$ fluctuations between $^{96}$Ru+$^{96}$Ru and $^{96}$Zr+$^{96}$Zr collisions, in agreement with measurements by the STAR Collaboration. We investigate how these scaling relations depend on the transport properties and extend this study to include the systems with similar mass numbers. This scaling approach towards heavy-ion observables demonstrates that isobar collision is a precision tool to probe the shape and radial structures, including the neutron skin, of the atomic nuclei across energy scales.
[1] J. Jia and C. Zhang, arXiv:2111.15559.
[2] C. Zhang and J. Jia, Phys. Rev. Lett. 128, 022301 (2022).
[3] G. Giacalone, J. Jia and C. Zhang, Phys. Rev. Lett. 127, 242301 (2021).
The chiral magnetic effect and chiral vortical effect enable us to probe possible local parity violation in hot dense matter created in heavy ion collisions. While equilibrium description is simple, the situation in heavy ion collisions can be quite far from equilbirum: the axial charge is likely to peak at early stage of the collisions [1-3], and the magnetic field and vorticity are also dominant at early stage. These require theoretical frameworks for out-of-equilibirum dynamics for chiral fermions. Chiral kinetic theory (CKT) offers such a framework. It has been derived based on field theory [4,5]. Previous works on CKT are organized as an expansion in hbar, which is valid for weak magnetic field. Its simplicity is lost at second order [6]. Recently, the CKT from Landau level basis is derived[7], which is valid for arbitrary magnetic field. In strong magnetic field limit, it reduces to CKT in the lowest Landau level approximation [8]. We will present a covariant chiral kinetic theory with Landau level basis. We use it to investigate a magnetized plasma with a transverse electric field and a steady vorticity as perturbations. We also study two-point functions from the above chiral kinetic theory which characterize the response to perturbative vector and axial gauge fields in magnetized chiral plasma.
[1]Yuji Hirono, Tetsufumi Hirano, and Dmitri E. Kharzeev, 1412.0311
[2]Yin Jiang, Shuzhe Shi, Yi Yin, and Jinfeng Liao, Chin. Phys., C42(1):011001, 2018
[3]Shu Lin, Li Yan, Gui-Rong Liang, Phys. Rev. C 98, 014903 (2018)
[4]Dam Thanh Son, Naoki Yamamoto, Phys.Rev.Lett.109:181602,2012
[5]M. A. Stephanov, Y. Yin, Phys. Rev. Lett. 109, 162001, 2012
[6]Jian-Hua Gao, Zuo-Tang Liang, Qun Wang, Xin-Nian Wang, Phys. Rev. D 98, 036019 (2018)
[7]Shu Lin, Lixin Yang, Phys.Rev.D 101 (2020) 3, 034006
[8]Koichi Hattori, Shiyong Li, Daisuke Satow, Ho-Ung Yee, Phys. Rev. D 95, 076008 (2017)
The Spin Hall Effect (SHE) is a generation of spin polarization for moving spin carriers in materials under an external electric field and is instrumental in investigating quantum effects in many-body systems [1]. Recent theoretical calculations indicate that the gradient of baryonic chemical potential (analogous to the electric field) can induce a sizeable spin Hall current in Au+Au collisions at $\sqrt{s_{NN}}$ $\sim$ 10 GeV. Furthermore, at the RHIC Beam Energy Scan (BES) energies, the sign as well as the pattern of energy dependence of the difference between the harmonics of spin polarization of $\Lambda$ and $\overline{\Lambda}$ hyperons, can be significantly different with and without the presence of baryonic spin Hall current [2-4].
In this talk, we will present the harmonic coefficients of $\Lambda$ hyperons' spin polarization ($P_{x} \sin(2\Delta\phi)$, $P_{y} \cos(2\Delta\phi)$, $P_{z} \sin(2\Delta\phi)$) as functions of transverse momentum, rapidity, and collision centrality in RHIC BES-II Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 14.6, 19.6, and 27 GeV. These measurements serve as the first experimental probe of the predicted baryonic SHE in heavy-ion collisions.
[1] Y. Kato el al., Science 306 (2004) 1910
[2] S. Liu et al., JHEP 07 (2021) 181
[3] B. Fu et al., Phys. Rev. Lett. 127 (2021) 142301
[4] B. Fu et al., arXiv: 2201.12970 (2022)
Femtoscopy is a tool that can be used to measure the space--time dimensions of the particle-emitting source created in heavy-ion collisions using two-particle correlations. Additionally to the measurement of the system size, one can extract the average pair-emission asymmetry between two particles with different masses. In this context, the measurement of femtoscopic correlations between charged pion and kaon pairs for different charge combinations obtained in Pb$−$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the LHC is presented. The spherical harmonics representations of the correlation functions ($C^0_0$ and $\Re C^1_1$) have been studied in different centrality bins. The obtained correlation functions are analysed after taking into account a precise treatment of the non-femtoscopic background. The extracted source size (R) and the pair emission asymmetry ($\mu$) show an increase from peripheral to central events. Moreover, it is observed that pions are emitted closer to the centre of the particle-emitting system than kaons and this result is associated to the hydrodynamic evolution of the system. Also, the source radii are found to be decreasing with increasing average momentum ($k_{\rm T}$) and transverse mass ($m_{\rm T}$) of the pair which indicates the presence of strong radial flow in the system.
Determination of equation of state for the nuclear matter at high baryon density region is one of the most important motivations for RHIC Beam Energy Scan program. Directed flow ($v_{1}$), which is the first harmonic coefficient in the Fourier expansion of the final state azimuthal distribution of produced particles relative to the collision reaction plane, is one of the sensitive probes for the early stages of collision dynamics.
The first phase of RHIC Beam Energy Scan (BES-I) program covers collision energies from $\sqrt{s_{\mathrm{NN}}}$ = 7.7 GeV to 200 GeV. We observed that $v_{1}$ slopes ($dv_{1}/dy|_{y=0}$) at mid-rapidity region for net-proton and net-$\Lambda$ show a minimum when collision energy is around $\sqrt{s_{\mathrm{NN}}}$ = 10-20 GeV [1]. The slope of $\phi$-meson $v_{1}$ has a hint of sign change between 11.5 and 14.5 GeV [2]. In this talk, we will present precision measurements of $v_{1}$ for pions, kaons, protons, and $\phi$-mesons using high statistics RHIC BES-II data for Au+Au collisions at 14.6 and 19.6 GeV. The corresponding $v_1$ slopes will be studied as a function of transverse momentum, rapidity, and collision centrality. The data will constrain the model calculations and provide important insights on the possible first order QCD phase transition.
[1] L. Adamczyk et al.(STAR Collaboration), Phys. Rev. Lett. 112, 162301 (2014).
[2] L. Adamczyk et al.(STAR Collaboration), Phys. Rev. Lett. 120, 062301 (2018).
The existence and location of the QCD critical point is an object of both
experimental and theoretical studies. Rich data recorded by NA61/SHINE
at SPS allow for a systematic search for non-monotonic dependence of
various correlation and fluctuation observables on collision energy and
size of colliding nuclei.
This contribution will review the NA61/SHINE studies of scaled factorial
moments of pion and proton multiplicity distributions, fluctuations of
conserved charges as well as multiplicity and multiplicity-transverse
momentum fluctuations.
The production mechanism of deuterons, which have a binding energy of 2.2 MeV, is a topic of current interest in high-energy heavy-ion collisions, where the system undergoes kinetic freeze-out at temperatures around 100 MeV. Two possible scenarios include (a) statistical thermal process and (b) coalescence of nucleons. Cumulants of deuteron number distributions and proton-deuteron correlations are sensitive to these physics scenarios. In addition, they are also sensitive to the choice of canonical versus grand canonical ensemble in statistical thermal models.
We report the first systematic measurements of collision energy and centrality dependence of cumulants (up to fourth order) of deuteron number distributions in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4, and 200 GeV. We will also discuss new measurements on proton-deuteron correlations. The measurements are performed in the STAR experiment at mid-rapidity ($|y|<$ 0.5) and within transverse momentum range 0.8 $< p_{T} ({\rm GeV}/c) <$ 4.0, using Time Projection Chamber and Time-of-Flight detectors. The experimental results are compared to the statistical thermal model calculations with a grand canonical, canonical ensemble, and the UrQMD model that incorporates the coalescence of nucleons close by in space and momentum to form deuterons. These theoretical comparisons with the experimental measurements provide key insights into the mechanism of deuteron production in high-energy heavy-ion collisions.
We have studied the effects of weak magnetic field and finite chemical potential on the transport of charge and heat in hot QCD medium by determining their response functions, such as electrical conductivity ($\sigma_{\rm el}$), Hall conductivity ($\sigma_{\rm H}$), thermal conductivity ($\kappa_0$) and Hall-type thermal conductivity ($\kappa_1$) in kinetic theory approach at weak magnetic field and finite chemical potential. The interactions among partons have been incorporated through their thermal masses. It is observed that, with the increase of magnetic field, $\sigma_{\rm el}$ and $\kappa_0$ decrease, and $\sigma_{\rm H}$ and $\kappa_1$ increase in the weak magnetic field regime, whereas the finite chemical potential increases these transport coefficients. The effects of weak magnetic field and finite chemical potential on aforesaid transport coefficients are found to be more conspicuous at low temperatures, whereas at high temperatures, they have only a mild dependence on magnetic field and chemical potential. We have found that the presence of finite chemical potential further extends the lifetime of magnetic field. This study is important to understand the effects of weak magnetic field and finite chemical potential on the local equilibrium through the Knudsen number, the elliptic flow, and the interplay between charge and heat transports through the Wiedemann-Franz law. The Knudsen number components in the weakly magnetized hot and dense QCD medium retain their values much below unity. Thus, there is sufficient separation between the mean free path and the characteristic length scale for the medium to remain in the local equilibrium state. Further, the elliptic flow gets increased in the presence of the weak magnetic field, whereas the presence of finite chemical potential decreases it. Furthermore, the Lorenz number components in the Wiedemann-Franz law are found to be strongly affected by the chemical potential than by the weak magnetic field. However, with the increase of temperature, the Lorenz number components are observed to increase, confirming the violation of the Wiedemann-Franz law for the hot and dense QCD medium in the presence of a weak magnetic field.
We recently devised a methodology within automatic differentiation (AD) which integrates our physics-priors into the specific IPs and deep learning representation together to perform Bayesian inference on the IPs. We demonstrated the developed methodology in several IPs raised in high energy nuclear physics (can also be easily generalized to other physics areas as well). (1) We first deploy the above AD-based approach to reconstruct spectral functions from Euclidean correlation functions which has been proven ill-posed especially with limited and noisy measurements. In our method the spectral is represented by DNNs while the reconstruction turns out to be optimization within AD under natural regularization to fit the measured correlators. We demonstrated and proved that the network with weight regularization can provide non-local regulator for this IP. Compared to conventional maximum-entropy-method (MEM), our method achieved better performance in realistic large-noise situation. It’s for the first time to introduce non-local regulator using DNNs for the problem and is an inherent advantage for the method, which can promisingly lead to substantial improvements in related problems and IPs. (2) We applied the method to reconstruct the fundamental QCD force – heavy-quark potential – from lQCD calculated bottomonium in-medium spectrum. Both the radius and temperature dependence of the interaction are well reconstructed via inverse the Schroedinger equation given limited and discretized bottomonium low-lying states mass and width. (3) We also demonstrated the method’s ability to infer neutron star EoS from astrophysical observables, with exciting results on closure tests for reasonable EoS reconstruction based on finite noisy M-R observables. Compared to conventional approaches our method holds unbiased representation for the EoS and bare interpretable Bayesian picture for the reconstruction.
At RHIC, a fireball forms in the Au-Au collision and rapidly cools during expansion, inside which the QCD matter undergoes a phase transition from quark-gluon-plasma to the hadronic phase. The phase transition signals are expected to be observed via the measurement of fluctuations of conserved charges such as baryon numbers [1]. Indeed, both the dynamical evolution and the spatially-nonuniform-temperature (and chemical potential) distribution of the fireball
affect the fluctuations of QCD phase transition. However, the current studies of the QCD phase transition mainly focus on the dynamical effects [2], and the nonuniform-temperature effects are overlooked.
In this talk, we will present the spatially-nonuniform-temperature effects on the QCD phase transition temperature, the fluctuations, and the correlation length via a simplified Ising-like model [3]. Different from the dynamical effects, which delay the phase transition, we reveal that the nonuniform-temperature effects lead to higher phase transition temperature. Besides, the suppression of the critical fluctuation can be as stronger as the dynamical slowing down effects, and the nonzero-momentum modes of fluctuations play a crucial role. Our study presents a different perspective to understand the recent STAR data and lattice results [4], and can be further generalized to other temperature-nonuniform systems like the compact stars.
[1] J. Adamet al. (STAR Collaboration), Phys. Rev. Lett.126,092301 (2021).
[2] M. Stephanov and Y. Yin, Phys. Rev. D98, 036006 (2018).
[3] Jun-Hui Zheng and Lijia Jiang, Phys. Rev. D 104, 016031 (2021)
[4] A. Bazavovet al.(HotQCD Collaboration), Phys. Lett. B795,15 (2019).
The study of event-by-event mean transverse momentum ($p_\mathrm{T}$) fluctutations is a useful tool to understand the dynamics of the system produced in ultrarelativistic heavy-ion collisions. The measurement of higher-order fluctuations of mean-$p_\mathrm{T}$ can help in probing the hydrodynamic behavior of the system and is considered to be a direct way of observing initial-state fluctuations. It can also be sensitive to the early-time evolution of the produced quark-gluon plasma.
We present the first measurement of three- and four-particle $p_\mathrm{T}$ correlators and their intensive ratios, related to the skewness and kurtosis of event-by-event mean-$p_\mathrm{T}$ distribution, as a function of average charged-particle density in Pb--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV and Xe--Xe collisions at $\sqrt{s_\mathrm{NN}}$ = 5.44 TeV using the data recorded by the ALICE detector. For the baseline study, the analysis is performed also in pp collisions at $\sqrt{s}$ = 5.02 TeV. The measurements are compared to corresponding results from the STAR experiment at lower collision energies and to different theoretical model predictions.
Strong magnetic fields are created at the early stage of non-central heavy-ion collisions. However, whether the magnetic fields survive in the late stage of heavy-ion collisions and experimental measurements of various observables are reminiscent of the initially-created magnetic fields still remain elusive. In this talk we show that fluctuations of and correlations among net baryon number, strangeness and electrical charge can be useful to probe the imprint of the magnetic field in heavy-ion collisions. This is based on the fact that 1) these fluctuations and correlations have been shown to be very useful in understanding the QCD phase structure in the vanishing magnetic fields and 2) our very recent lattice QCD studies on these quantities in magnetic fields.
We will show the first lattice QCD results of the second-order fluctuations of and correlations among net baryon number, electric charge and strangeness in (2+1)-flavor lattice QCD in the presence of a background magnetic field. Lattice QCD simulations are performed on 32^3×𝑁𝜏 lattices using the highly improved staggered fermions in a fixed scale approach with 𝑁𝜏∈[8,96] [1,2]. We study these quantities from zero temperature up to ∼1.7 𝑇𝑝𝑐 with 15 values of the magnetic field strength 𝑒𝐵∈[0,60$m^2_\pi$] with pion mass $m_\pi$=220 MeV [1]. We also extend the above lattice QCD studies to the realistic case with physical pion mass $m_\pi$=135 MeV, and focus on a smaller temperature interval around the pseudo-critical temperature ranging from 0.9 𝑇𝑝𝑐 to 1.1 𝑇𝑝𝑐. To mimic the magnetic field strength produced in the early stage of heavy-ion collision experiments we now have 6 different values of the magnetic field strength up to ∼10$m^2_\pi$ with $m_\pi$=135 MeV [3].
We discuss the temperature and 𝑒𝐵 dependences of the second-order fluctuations of and correlations among net baryon number, electric charge and strangeness. We find that these second-order fluctuations and correlations are substantially affected by 𝑒𝐵. They even develop peak structures at sufficiently large 𝑒𝐵 which could be related to a possible critical end point in the 𝑇−𝑒𝐵 plane. We propose to investigate these quantities in experiments in different centrality classes and collision systems where 𝑒𝐵 could be different.
We present our efforts to determine the QCD phase diagram using Complex Langevin simulations. These are lattice calculations, which allow direct simulations at non-zero chemical potential. Here we use two flavours of naive Wilson fermions with not too heavy pion masses ($\sim 480$ MeV). We report on our findings across the temperature-density plane. In addition, we also show our efforts to include strangeness in the simulation.
A major challenge for the upcoming heavy-ion collision programmes around the world is to develop fast, accurate techniques to analyze the large amounts of data produced in the experiments. Novel data analysis techniques are necessary in the experiments to quickly identify events with interesting physics for further analyses and permanent storage. In this talk, we show that PointNet based Deep Learning (DL) models can be deployed for online event characterisation in heavy-ion collision experiments. In particular, we demonstrate that PointNet based models can perform, event-by-event impact parameter reconstruction at CBM experiment using directly the hits/ tracks of particles from the detector planes [1, 2]. The models have their mean error varying from -0.33 to 0.22 fm for impact parameters 2-14 fm and outperform conventional methods based on a single observable such as track multiplicity. We also show that PointNet models can accurately identify the nature of QCD transition at the CBM experiment [3]. The DL models distinguish a first order phase transition from a crossover transition using the reconstructed tracks of charged particles with an accuracy of up to 99.8%. The models are also shown to outperform methods relying on conventional mean observables.
References
[1] Omana Kuttan, M., Steinheimer, J., Zhou, K., Redelbach, A., & Stoecker, H. (2020). A fast centrality-meter for heavy-ion collisions at the CBM experiment. Physics Letters B, 811, 135872
[2] Omana Kuttan, M., Steinheimer, J., Zhou, K., Redelbach, A., & Stoecker, H. (2021). Deep Learning Based Impact Parameter Determination for the CBM Experiment. Particles, 4(1), 47-52.
[3] Omana Kuttan, M., Zhou, K., Steinheimer, J., Redelbach, A., & Stoecker, H. (2021). An equation-of-state-meter for CBM using PointNet. Journal of High Energy Physics, 2021(10), 1-25.
We investigate the impact of a first-order chiral phase transition and critical point on hadron multiplicity ratios. We model the dynamical expansion of the hot and dense matter created in a heavy ion collision with a Bjorken hydrodynamics expansion coupled to the explicit evolution of the chiral order parameter at center-of-mass energies from 2 to 10 GeV. Hereby, the chiral dynamics is implemented using a Langevin equation including dissipation and noise. We find a strong enhancement of the entropy-per-baryon S/A at lowest energies which is created at the non-equilibrium first-order phase transition. By mapping the initial and final S/A to a hadron resonance gas, we are able to quantify the shift of hadron multiplicity ratios.
We perform the first study on asymmetric longitudinal decorrelations of elliptic, triangular and quadrangular flows in proton-nucleus collisions at the LHC and RHIC energies. To measure the longitudinal flow decorrelations for asymmetric collision systems, we propose a new set of rapidity-asymmetric flow decorrelation functions. Our event-by-event hydrodynamic calculations show that the flow decorrelations in proton-going direction are larger than those in nucleus-going direction. We also find that proton-nucleus collisions at RHIC have larger longitudinal flow decorrelation effects than those at the LHC. Our study opens a new window to probe the longitudinal properties and the origin of flows in relativistic nuclear collisions.
Two-particle Bose-Einstein quantum-statistical correlations of charged
kaons were measured at $\sqrt{s_{NN}} = 200$ GeV collision energy by the
PHENIX experiment. Encouraged by previous results, a Levy-shaped particle
emitting source was assumed and the parametrizations of the measured
correlation functions were performed accordingly. The shape of these
functions is characterized by the Levy exponent $\alpha$ while the width
of the distribution is described by Levy scale $R$. Taking into account
for the core-halo picture of the source, the $\lambda$ intercept
parameter can be introduced. These three parameters and their
combinations were investigated as the function of transverse mass and
the results were compared to previous measurements of pion-pion
correlations measured by the PHENIX experiment. The comparison could
shed light on the origin of the Levy distribution in two-particle
correlations and the possibly physical interpretation of its parameters.
The Kondo effect in metals is induced by a spin exchange interaction between conduction electrons and localized impurities. This effect drastically modify electric/thermal/transport properties of metals at low temperatures. In high-density quark matter, a similar effect can be induced by interactions between light quarks and colored impurities like charm or bottom quarks, which is the so-called QCD Kondo effect. The appearance of such a new type of Kondo effect can change the structure of the QCD phase diagram and heavy-quark transport phenomena.
The nonperturbative region of the Kondo effect can be described by a Kondo condensate composed of a light fermion and a heavy impurity, and the structure of the QCD phase diagram including such a phase is an open question [1,2,3]. In this talk, based on our recent studies, I will review novel phenomena realized in the QCD Kondo phase, such as excited states in the Kondo phase [2,4], a Kondo effect by chirality imbalance [5], contributions by antiparticle impurities [6], an enhancement of the chiral separation effect [7,8], a phase structure in lattice models [9], and a heavy-quark spin polarization [7,10].
[1] Nucl. Phys. A 983, 90 (2019) [arXiv:1604.07208]
[2] Phys. Rev. D 96, 014016 (2017) [arXiv:1703.04124]
[3] Phys. Rev. D 96, 114007 (2017) [arXiv:1708.06930]
[4] Phys. Rev. Research 2, 023066 (2020) [arXiv:1909.07573]
[5] Phys. Rev. Research 2, 023312 (2020) [arXiv:1912.12669]
[6] Phys. Rev. Research 3, 013233 (2021) [arXiv:2008.08434]
[7] Phys. Rev. Research 3, 023098 (2021) [arXiv:2011.00882]
[8] Phys. Rev. D 103, 054041 (2021) [arXiv:2012.15173]
[9] Phys. Rev. D 104, 094515 (2021) [arXiv:2107.07270]
[10] arXiv:2109.14799
We calculated the shear viscosity of strange and non-strange hadrons
produced in central gold-gold collisions at intermediate energies. For
calculations of the collisions the transport model UrQMD is employed.
The shear viscosity is obtained within the Green-Kubo formalism. The
hadron resonance gas model is used to determine temperature and chemical
potentials of baryon charge and strangeness out of microscopic model
calculations. Then, we determine the partial viscosity of main hadron
species, such as nucleons, pions, kaons and Lambdas. The decrease of
the beam energy from $E_{lab} = 40$~AGeV to 10~AGeV leads to rise of
baryon shear viscosity accompanied by drop of shear viscosity of mesons.
In contrast to that of non-strange hadron species, the shear viscosity
of kaons and Lambdas remains independent on energy within the studied
energy range. Its ratio over the entropy density increases with the
drop of temperature and rise of baryon chemical potential.
Extraction of the Quark-Gluon Plasma (QGP) transport properties (i.e. specific shear viscosity $\eta/s$) is a prime goal of the heavy-ion programs at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC). Correlators that are sensitive to both initial-state effects and final-state viscous attenuation can give invaluable constraints for temperature ($T$) and chemical potential ($\mu_{B}$) dependence of $\eta/s$. The $\rho(v^{n}_{2},\langle p_{T} \rangle)$ correlator, that gives the strength of the correlation between an event’s mean-transverse momentum $[p_{\mathrm{T}}]$ and its $v_2$ magnitude, shows more sensitivity to the initial state than to final stat effects~[1--2]. A comprehensive set of $v_n^2$, $[p_{T}]$, ${\rm cov}(v_{2}^{2},[p_T])$ and $\rho(v^{2}_{2},\langle p_{T} \rangle)$ calculations for Au+Au collisions spanning the beam energy range $\sqrt{s_{\rm NN}}$ = 2760--19.6 GeV using the Hydro-hybrid, AMPT and EPOS models, will be presented for several centralities and event shape selections. Our simulated results~[1--2] show characteristic beam-energy-dependent and event shape trends that can give significant constraints for the respective influence of initial-state fluctuations, system-size, system-shape, and $\eta/s(\mu_{B},T)$.
[1] N. Magdy, et al., Phys.Lett.B 821 (2021) 136625
[2] N. Magdy, et al., arXiv:2111.07406
At LHC energies it is possible to generate BSQ (baryon, strangeness, and electric) charge fluctuations from gluon splittings into quark anti-quark pairs, generated within the ICCING model. Here we propagate these conserved charges within an upgraded version of the hydrodynamic model, v-USPhydro, that conserves BSQ coupled to a 4-D equation of state {T,μB,μS,μQ} from Lattice Quantum Chromodynamics. We find that solely due to charge fluctuations that we expect large fluctuations in the chemical potentials {μB,μS,μQ} in local fluid cells at freeze-out even at LHC energies.
Functional forms of the neutron star Equation of State (EoS) are required to extract the viable EoS band from neutron star mergers. Typically, one of three methods are used-- spectral functions, piecewise polytropes, or gaussian process estimations. However, realistic nuclear EoS, containing deconfined quarks or hyperons, present nontrivial features in the speed of sound such as bumps, kinks, or plateaus. These features in the speed of sound cannot be captured well by the currently used methods for the functional forms [1]. We modify gaussian processes by introducing spikes and plateaus in the speed of sound and combine our new EoS method with an active learning framework to quickly rule out EoS that do not fit within constraints from NICER and gravitational waves. We find these new features play a role in understanding ultra-heavy neutron stars that support stellar masses compatible with GW190814.
[1] Tan et al, Phys.Rev.Lett. 125 (2020) 26, 261104
The LHCb spectrometer has the unique capability to function as a fixed-target experiment by injecting gas into the LHC beampipe while proton or ion beams are circulating. The resulting beam+gas collisions cover an unexplored energy range that is above previous fixed-target experiments, but below the top RHIC energy for AA collisions. Here we present new results on antiproton and charm production from pHe, pNe, and PbNe fixed-target collisions at LHCb. Comparisons with various theoretical models of particle production and transport through the nucleus will be discussed.
A non-equilibrium effective field theory framework has recently been formulated for fluctuating hydrodynamics [1]. In this talk, we present an example of applying this novel formalism to study the critical properties of QCD. In the view that non-Gaussian fluctuations of baryon density are important for the QCD critical point search, we derive evolution equations for the critical non-Gaussian fluctuations of a conserved density and obtain closed-form solutions based on field theory techniques [2]. Those results can be readily implemented for simulations in realistic situations of heavy-ion collisions. In addition, we find that nonlinear interactions among noise fields, which are missing in traditional stochastic hydrodynamics, could potentially contribute to the quartic (fourth-order) fluctuations in the scaling regime in off-equilibrium situations.
[1] Michael Crossley, Paolo Glorioso, and Hong Liu, “Effective field theory of dissipative fluids,” JHEP 09 (2017) 095.
[2] Noriyuki Sogabe and Yi Yin, “Off-equilibrium non-Gaussian fluctuations near the QCD critical point: an effective field theory perspective,” JHEP (to appear) [arXiv:2111.14667 [nucl-th]].
Fluctuations of conserved charges in a grand canonical ensemble can be computed on the lattice and, thus, provide theoretical input for freeze-out phenomenology. Electric charge fluctuations and the corresponding higher order correlators are extremely difficult, suffering form the most severe lattice artefacts.
We present new simulation data with a novel discretization where these effects are strongly suppressed and provide continuum extrapolated results in the temperature region of the chemical freeze-out.
The spin Hall effect (SHE) is a generation of spin polarization for moving spin carriers in materials under an external electric field and has been observed in semiconductors, metals, and insulators at or below room temperature. Recent theoretical analyses show that spin Hall current can be induced by the baryon chemical potential gradient which plays the role of the analogous electric field and which becomes sizable in the fireballs created in heavy-ion collisions at beam energy of O(10) GeV. In this talk, we focus on this important mechanism and predict the signature of the SHE using a (3+1) D viscous hydrodynamic model MUSIC with AMPT initial condition. We propose to use the second Fourier coefficients of the net spin polarization of Lambda hyperon as sensitive probes to search for the SHE. Those SHE observables show a qualitative difference in both the sign and beam energy dependence for the situations with and without the SHE. Future experimental observation of these distinct qualitative features would provide strong evidence for the existence of the SHE in the hot and dense QCD matter at trillions of degrees.
Light (anti-)nuclei produced in relativistic heavy-ion collisions, due to their composite structures, naturally encode the many-nucleon correlations. The light nuclei production is thus sensitive to the density fluctuation/correlation developed during the non-smooth phase transition from QGP to hadronic matter in relativistic heavy-ion collisions， providing a unique tool to probe the conjectured QCD critical point in the Beam Energy Scan program. In this talk, we present the most recent results of energy dependence of $N_tN_p/N_d^2$ in the vicinity of a first-order chiral phase transition. The dynamics of chiral phase transition is modelled within a Lagrangian-based transport model approach.
The azimuthal anisotropies observed in small systems can originate from the final state response to the initial geometry as well as from initial momentum anisotropies. Recently it has been proposed that the correlation between the flow coefficient $v_{2}^2$ and the mean $p_\mathrm{T}$ carries information on the origin of flow in small collision systems by showing a characteristic sign change at very low multiplicity. However, this sign change exists in PYTHIA8 events as a result of nonflow effects. To reduce the nonflow dependence , a new correlator that correlates multiparticle cumulants and mean $p_\mathrm{T}$ is suggested. In this talk, we present results for this correlator using two and four particle correlations in pp, pPb and peripheral PbPb collisions. We also report our high precision measurements of $v_{2}$ using four-, six-, and eight-particle correlations, together with $v_{3}$ from four particle correlations, in both pPb and peripheral PbPb collisions. The ratios between $v_{n}$ harmonics involving different numbers of particles are compared to model calculations to study the fluctuation-driven initial state anisotropies. The results provide insights to the origin of flow in small collision systems.
Anisotropic flow of the medium formed in heavy-ion collisions is a sensitive observable to the equation of state and transport properties of the medium. The third order anisotropy known as triangular flow ($v_{3}$) arises mainly due to the fluctuations present in the initial stages of the colliding nuclei. The triangular flow is found to be more sensitive to the transport property such as viscosity to entropy density ratio ($\eta/s$), compared to the elliptic flow ($v_{2}$) [1]. Hence systematic measurements of $v_{3}$ at different energies are useful to constraint the temperature dependence of $\eta/s$ of the produced medium.
STAR has recently finished the data taking for RHIC Beam Energy Scan Phase-II (BES-II) program with higher statistics, improved detector condition, and wider pseudorapidity coverage compared to what was available during BES-I program. In this talk, we will present the measurements of $v_{3}(p_{T})$ of identified hadrons, specifically strange and multi-strange hadrons ($K_{S}^{0}$, $\Lambda$, $\bar{\Lambda}$, $\phi$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, and $\bar{\Omega}^{+}$) using high statistics BES-II data at mid-rapidity ($|y| < 1.0$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 14.5, and 19.6 GeV. The difference in $v_{3}$ between baryon to anti-baryons will be shown. A test of the number of constituent quark (NCQ) scaling, centrality dependence, and the collision energy dependence of $v_{3}$ will be presented. The results will be compared to $v_{2}$ measurements for the same kinematics and to the predictions from a multi-phase transport model. Finally, the physics implications of our measurements in the context of the initial state and transport properties of the medium produced at BES-II energies will be discussed.
[1] B. Schenke, S. Jeon, and C. Gale, Phys. Rev. Lett. 106, 042301 (2011).
Hypernuclei are bound nuclear systems of correlated nucleons and hyperons. Therefore, the production of hypernuclei in heavy-ion collisions provides an experimental avenue for studying hyperon$-$nucleon (Y-N) interaction, which is an important ingredient, not only in the equation-of-state of astrophysical objects such as neutron stars, but also in the description of the hadronic phase of a heavy-ion collision. The strength of the Y-N interaction can be investigated by measuring the properties of hypernuclei. For example, light $\Lambda$-hypernuclei containing one hyperon are conventionally understood as a weakly bound system of a $\Lambda$ and a nucleus, suggesting their lifetimes are close to the free-$\Lambda$ lifetime.
In heavy-ion collisions, light hypernuclei are expected to be abundantly produced at low collision energies due to the high baryon density. In this presentation, we will report precise lifetime measurements of $^3_{\Lambda}$H, $^4_{\Lambda}$H, and $^4_{\Lambda}$He in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV and 7.2 GeV, recorded by the STAR experiment at RHIC in the fixed-target mode in 2018. The results will be compared with model calculations and physics implications will be discussed.
We compute electro-production of P_c(4312) in e^-+p^+→e^-+P_c using Vector Dominance Model assuming four possible spin parity of P_c (4312),J^P=(1/2)^±,(3/2)^±. Electron Ion Collider which is to be built at Brookhaven National Laboratory, we can collide not only unpolarized beam of electron and proton, but also polarized beam so we can investigate more deeply about the angular distribution of P_c (4312). Using high integrated luminosity of Electron Ion Collider, we can predict the yield of P_c (4312) for each spin-parity. We also plot differential scattering cross-section for both unpolarized and polarized beam as a function of pseudorapidity of P_c (4312) in the Lab frame and transverse momentum. Forward to Backward Ratio and Beam Spin Asymmetry helps us to discriminate spin of P_c (4312). Furthermore to specify parity, we study the effect of transverse and longitudinal polarization of J⁄ψ on decay width of P_c→p+J⁄ψ→p+e^-+e^+ channel.
The addition of a Forward Calorimeter (FoCal) to the ALICE experiment is proposed for LHC Run 4 to provide unique constraints on the low-x gluon structure of protons and nuclei via forward measurements of direct photons. A new high-resolution electromagnetic Si-W calorimeter using both Si-pad and Si-pixel layers is being developed to discriminate single photons from pairs of photons originating from $\pi^0$ decays. A conventional sampling hadron calorimeter is foreseen for jet measurements and the isolation of direct photons. In this presentation, we will report on results from test beam campaigns in 2019 and 2021 at DESY and CERN with Si-pad and pixel modules, a first prototype for the hadronic calorimeter, and a full-pixel calorimetry prototype based on ALPIDE sensors.
Final-state effects on J/ψ nuclear modification in A+A collisions have long been observed in heavy-ion physics at RHIC and LHC energies. Suppression of the $J/\psi$ nuclear modification factor has been considered a signature of quarkonia dissociation in large systems, where energy densities reach levels high enough to break bound $c\bar{c}$ states. However, suppression of the $J/\psi$ nuclear modification factor has also been observed in small collision systems, prompting questions about whether the modification could be due to final-state effects. Here we present $J/\psi$ measurements as a function of rapidity and transverse momentum by the PHENIX Collaboration for three different systems: p+Al, p+Au, and 3He+Au collisions at center of mass energy $\sqrt{s_\mathrm{NN}}=200\mathrm{GeV}$, to investigate the origin of this suppression. Results are compared between collision systems, as well as to gluon shadowing and Transport Model predictions.
Early production of heavy quarks (charm and bottom) in the heavy-ion collisions
and their associated large mass scale renders them as useful probes for studying the quark-gluon plasma (QGP) properties. We study the heavy quark transport coefficients, drag and momentum diffusion, as a function of their initial momentum and QGP temperature for elastic and inelastic processes. The thermal medium interactions are incorporated through the effective fugacity quasiparticle model. The viscous corrections are included up to first and second order in the thermal distribution function of in-medium particles by solving effective Boltzmann equation within relaxation time approximation. The effect of shear and bulk viscous corrections to the heavy-quark transport coefficients have been investigated.
We present the results of the axial-vector transition form factors of
singly heavy baryons within the framework of the chiral quark-soliton
model. The chiral quark-soliton model is a pion mean-field approach in
the large-$N_{c}$ limit, which deals with light and heavy baryon
on and equal footing. In the limit of the infinitely heavy mass of the
heavy quark, a singly heavy baryon can be regarded as $N_{c}-1$
valence quarks bound by the pion mean fields with the heavy quark as a
color static source. We include the $1/N_{c}$ rotational corrections
and the effects of SU(3) flavor symmetry breaking. We first compare
the results for $C_{5}^{A}(q^2)$ of the heavy baryon transitions with
those for the well-known $\Delta\to p$ transitions. We also discuss
the results for the axial mass for the heavy baryon transitions.
Although signatures of collectivity in high-multiplicity pA collisions suggest possible final-state interactions, an unambiguous search of jet quenching in small collision systems is still missing. Using quark mass as another handle, heavy-flavor observables can shed light on different mechanisms of jet modification in $p$-Pb, $d$-Au, and O-O collisions. We employ a coupled DGLAP evolution framework that takes advantage of the medium-modified QCD splitting functions recently obtained in SCET${}_G$ and incorporates HTL-motivated collisional energy loss effects and initial-state parton modification in the cold nuclear matter. With the jet-medium couplings constrained to the nuclear modification factor of charged hadrons $R_{AA}^{h^{\pm}}$ in Pb-Pb collisions, we predict $D$- and $B$-meson $R_{AA}$ in Xe-Xe, O-O, and p-Pb collisions at the LHC and $d$-Au collisions at RHIC. We find suppression that scales non-trivially with the quark mass and medium sizes. We further analyzed the impact of the initial-state cold nuclear matter effects on the search for QGP signatures in small colliding systems.
We present a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive-charged particle yields in 13 TeV pp collisions. Measurements are made differentially for Upsilon momentum and for different Upsilon states. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV pp data. A description of the technical challenges associated with a heavy-ion style analysis in high-pileup pp data will be shown, as well as the results and their physics implications.
Heavy quarks, such as charm and bottom quarks, and their quarkonium bound states are very useful internal probes of the hot and dense medium, Quark gluon-plasma, created in heavy-ion collisions. They are created in the collisions and are appreciably affected by the medium. This leads to distinctive features in their observed final yields which carries information about the bulk properties of the medium. I discuss the heavy quark potential modification due to the relative motion between the heavy quark and the QGP medium and corresponding changes in quarkonium states. We show the real and imaginary parts of the medium modified quarkonia potential and obtain their binding energies and the dissociation widths. It will be shown that the screened potential becomes strongly anisotropic as the velocity of the heavy quark increases and its possible effects on the modification of quarkonium states.
Heavy quark production is an important experimental observable that sheds light on the heavy quark interaction with the nuclear medium. With high statistics datasets, tracking and PID at very low transverse momentum, and excellent vertexing capabilities, LHCb performs precision measurements of a rich set of heavy flavor hadrons, including open charm hadrons and charmonia. These capabilities allow for precise studies of charm production, baryon enhancement and charmonia suppression in various colliding systems from $pp$ to $p$Pb and PbPb. Furthermore, the production of the exotic $X$(3872) and $T_{cc}^{+}$ hadrons in $pp$ and $p$Pb collisions is also studied. We will present these results along with comparisons to theoretical calculations.
Utilizing a thermodynamic T-matrix approach for heavy-quark (HQ) transport in the quark-gluon plasma (QGP) we compute the effects of spin-dependent interactions between partons. Based on the vacuum Cornell potential, we first confirm that the experimental values of the mass splittings in quarkonia are improved by employing a confining potential that is a mixture of vector and scalar potentials rather than a purely scalar one. We then apply the improved potential to calculate the in-medium parton spectral functions and scattering amplitudes at finite temperature self-consistently. The temperature corrections to the in-medium potential are constrained by thermal lattice-QCD “data” for the HQ free energy and equation of state. Employing these results to calculate the in-medium charm-quark transport coefficients in the QGP, we find that the mixing effect for confining potential enhances the momentum dependence of the drag coefficient, A(p), over previous calculations with a purely scalar potential, thereby also decreasing the pertinent diffusion coefficients, Ds. The refined microscopic description of HQ transport in the QGP is likely to improve the pertinent phenomenology of open heavy-flavor observables at RHIC and the LHC.
We present a systematic method for solving the Lindblad equation for heavy-quarkonium dynamics in the quark-gluon plasma which accounts for corrections that are next-to-leading order (NLO) in the ratio of the binding energy of the state and the temperature. The method used relies on mapping the three-dimensional Lindblad evolution to the solution of the one-dimensional Schrodinger evolution with stochastically sampled quantum jumps. We demonstrate how to achieve this dimensional reduction by writing the NLO effective Hamiltonian and jump operators in the spherical basis in which operators act only on the reduced radial part of the wave function. As a result, one can implement the quantum trajectories method to solve the NLO Lindblad equation. Using the resulting NLO framework we can more reliably extend the calculation of heavy-quarkonium suppression to lower temperatures than is possible with the LO formalism.
We show that the same QCD formalism that accounts for the suppression of high-$p_T$ hadron spectra in heavy-ion collisions predicts a medium-enhanced $c\bar{c}$-pair production in high-$p_T$ jets. We study the feasibility of detecting this new medium induced phenomena in the upcoming and future high-luminosity heavy ion runs.
Heavy flavor production provides a unique probe for studying the transport properties of the quark-gluon plasma (QGP) formed in high-energy nuclear collisions. Experimental observables like the nuclear modification factor $R_{AA}$ and elliptic anisotropy $v_{2}$ of heavy flavor mesons are sensitive to the heavy quark diffusion coefficient. There now exist an extensive set of such measurements, which allow a data-driven extraction of this coefficient. In this work[1], we make such an attempt within our recently developed heavy quark transport modeling framework (Langevin-transport with Gluon Radiation, LGR[2-4]). A question of particular interest is the temperature dependence of the diffusion coefficient, for which we test a wide range of possibilities and draw constraints by comparing relevant charm meson data with model results. We find that a relatively strong increase of diffusion coefficient from crossover temperature $T_{c}$ toward high temperature is preferred by data.
Furthermore, We have made predictions for Bottom meson observables down to the low momentum region for further experimental tests[5]. It is found that our calculations can describe simultaneously $R_{AA}$ and $v_{2}$ data for the prompt and non-prompt $D^{0}$ mesons in central ($0-10\%$) and semi-central ($30-50\%$) Pb--Pb collisions at $\sqrt{s_{\rm NN}}=5.02~{\rm TeV}$. Recently, we employ a soft-hard factorized model, which combines a thermal perturbative description of soft scatterings and a perturbative QCD-based calculation for hard collisions, we check the energy and temperature dependence of the heavy quark diffusion coefficients in Langevin dynamics[6]. With the parameter-optimized model, we find that a small value of the spatial diffusion coefficient at transition temperature is preferred by data $2\pi TD_{s}(T_{c}) \simeq 6$.
[1] S. Li and J. F. Liao, Data-driven extraction of heavy-quark diffusion in quark-gluon plasma, Eur. Phys. J. C, 80, 671 (2020)
[2] S. Li, C. W. Wang, X. B. Yuan, and S. Q. Feng, Production of open-charm mesons in relativistic heavy-ion collisions, Phys. Rev. C, 98, 014909 (2018)
[3] S. Li and C. W. Wang, Charm-strange meson production in ultrarelativistic heavy-ion collisions at energies available at the CERN Large Hadron Collider, Phys. Rev. C, 98, 034914 (2018)
[4] S. Li, C. W. Wang, R. Z. Wan, and J. F. Liao, Probing the transport properties of quark-gluon plasma via heavy-flavor Boltzmann and Langevin dynamics, Phys. Rev. C, 99, 054909 (2019)
[5] S. Li, W. Xiong, and R. Z. Wan, Relativistic Langevin dynamics: charm versus beauty, Eur. Phys. J. C, 80, 1113 (2020)
[6] S. Li, F. Sun, W. Xie, W. Xiong, Langevin dynamics of heavy quarks in a soft-hard factorized approach, Eur. Phys. J. C, 81, 536 (2021)
\begin{abstract}
Recent experiments have observed large anisotropic collective flows in high multiplicity proton-lead collisions at the Large Hadron Collider (LHC), which indicates the possible formation of mini quark-gluon plasma (QGP) in small collision systems.
However, no jet quenching has been confirmed in such small systems so far.
To understand this intriguing result, the system size scan experiments have been proposed to bridge the gap between large and small systems.
In this work, we perform a systematic study on both heavy and light flavor jet quenching in different collision systems at the LHC energies.
The productions of hard jet partons and hadrons are calculated within a next-to-leading-order perturbative QCD framework, the evolution of heavy and light jet partons inside the QGP is simulated via a linearized Boltzmann transport model, and the space-time profile of the QGP fireball is obtained via a (3+1)-dimensional viscous hydrodynamics simulation.
Using our state-of-the-art jet quenching model, we provide a a good description of nuclear modification factor $R_{\rm AA}$ for charged hadrons and $D$ mesons in central and mid-central Pb+Pb and Xe+Xe collisions measured by CMS collaboration.
We further predict the transverse momentum and centrality dependences of $R_{AA}$ for charged hadrons, $D$ and $B$ mesons in Pb+Pb, Xe+Xe, Ar+Ar and O+O collisions at the LHC energies.
Our numerical results show a clear system size dependence for both light and heavy flavor hadron $R_{AA}$ across different collision systems.
This study provides a smooth transition for jet quenching from large to small systems, which helps to identify the unique signatures of QGP droplet and search for the disappearance of QGP in relativistic nuclear collisions.
Motivated by the study of beauty quarks to probe the evolution of the nuclear medium, we performed a measurement of the $B^{+}$ meson production $pPb$ collisions and its nuclear modification factor. We present the results as a function of $p_{T}$ and charged multiplicity, using data recorded with the CMS detector in 2013 (5.02 TeV) and 2016 (8.16 TeV). The results are presented in a large $p_T$ range and a wide pseudo-rapidity interval with a comparison with the FNOLL calculations. These measurements contribute to characterize effects of beauty quark diffusion, energy loss and the understanding of its collective behavior.
The definitive confirmation of gluon saturation effects in high energy hadronic collisions is still outstanding. A promising route to pin down saturation effects is the simultaneous study of vector meson and charged hadron production. Heavy vector mesons, whose mass is of the order of magnitude of the saturation scale, are expected to be less sensitive to saturation effects than lighter charged hadrons. Then, varying the collision system and/or the vector meson rapidity one can probe different degrees of saturation systematically. In this talk, based on [1], we introduce a theoretical setup to compute $J/\psi$ and hadron production within the color glass condensate with energy evolution described by the running coupling Balitsky-Kovchegov equation. Unlike previous works, our setup includes geometric and saturation scale normalization fluctuations that dynamically generate the event-by-event multiplicity fluctuations of both hadrons and $J/\psi$. We find that these fluctuations strongly impact the degree of saturation effects. Overall, we demonstrate that experimental data on heavy-flavour production as a function of event activity, e.g. [2], provide stringent constraints on the fluctuating proton structure and, more generally, on saturation dynamics.
Relativistic heavy-ion collisions provide a unique opportunity to investigate properties of nuclear matter under extremely strong electromagnetic field. Using a heavy quark transport model that includes both collisional and radiative energy loss of heavy quarks, coupled to a (3+1)-dimensional viscous hydrodynamic model CLVisc, we study the initial longitudinal energy density distribution and the time evolution of electromagnetic field via both soft and heavy flavor hadron observables. With a systematic comparison between three different initial energy density profiles – Bozėk-Wyskiel, CCNU and Shen-Alzhrani, we find a counter-clockwise tilt of the initial geometry in the reaction plane is crucial for understanding the rapidity dependence of directed flow (v1) of both soft hadrons and D mesons at RHIC and LHC. Meanwhile, the difference of v1 between D and Dbar is shown to be sensitive to the time evolution behavior of the electromagnetic field that generates opposite forces on c and cbar. This time evolution behavior is shown to be further constrained by the elliptic flow (v2) of soft hadrons due to the force density (squeezing effect) induced by the magnetic field inside the paramagnetic QGP medium. Therefore, a simultaneous description of soft and heavy flavor hadron v1 and v2 is required for a stringent constraint on the properties of electromagnetic field produced in high-energy nuclear collisions. Additional observables, such as the angular dependence of heavy meson RAA, and v1 of heavy flavor decayed leptons are predicted, which can be tested by experimental measurements in the near future.
Our understanding of hadronic collisions has been challenged by the intriguing observation of collective phenomena in events with high charged-particle multiplicity density in small systems. Such high multiplicities are expected in events with multiple parton-parton interactions (MPI). At the LHC, MPIs affect the production of heavy-quarks (charm and beauty), and the large statistics samples available allow for the study of quarkonium production in association with other particles as well as of their relation to the underlying event. In proton-proton (pp) collisions, the study of pair production of quarkonia in the same event, besides helping to disentangle among different production mechanisms, is sensitive to double-parton scattering. Multiplicity dependent studies of quarkonia are fundamental for investigating the correlations between soft and hard components of high-multiplicity events in small collision systems. In particular, excited quarkonium states, characterized by lower binding energies than the corresponding ground states, are more sensitive to any possible dissociation mechanism at play at high multiplicities.
In this contribution, new multiplicity dependent results of excited quarkonium states, such as ψ(2S), Υ(2S) and Υ(3S), reconstructed in pp and p-Pb collisions at forward rapidity, along with the corresponding excited-to-ground state ratios, will be presented. New measurements for J/ψ will be also discussed. These include the first measurement of J/ψ pair production in pp collisions at √s = 13 TeV, as well as the latest results on J/ψ production as a function of multiplicity at forward rapidity in pp collisions at √s = 5.02 and 13 TeV. The status of similar multiplicity dependent measurements at midrapidity in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 will be shown. The comparison with available models will also be discussed.
Quarkonia and tetraquark production have been long-standing puzzles in particle physics. The polarisation measurement of J/ψ is expected to have significant transverse polarisation at large pT, but has been experimentally observed to be consistent with zero. Hard production of onia processes using NRQCD formalism are available in MC generators, such as Pythia8. However, these processes alone cannot fully describe the data. Here, we will present results from LHCb measuring the production of quarkonia in jets.
While the 3D charge distribution of the nucleon cannot be interpreted as quantum-mechanical probability densities in the Wigner sense, the 2D charge distribution of it has a completely probabilistic meaning. In this talk, we present how the Abel transformation map the 3D charge distribution in the Breit frame onto the 2D charge one in the infinite momentum frame.
We investigate the gravitational form factors of the baryon octet within the framework of the chiral quark-soliton model, also known as the pion mean-field approach, emphasizing the effects of flavor SU(3) symmetry breaking on the
form factors. The D-term form factors provide information on the stability conditions of the baryon octet in terms of the pressures and shear forces inside them. We show explicitly that the stability conditions are well preserved in the
presence of flavor SU(3) symmetry breaking. We also discuss various physical implications of the gravitational form factors of the SU(3) baryon octet.
While it is well known that there is a significant amount of conserved charges in the initial state of nuclear collisions, the production of these due to gluon splitting has yet to be thoroughly investigated. The ICCING (Initial Conserved Charges in Nuclear Geometry) algorithm [1] reconstructs these quark distributions, providing conserved strange, baryon, and electric charges, by sampling a given model for the $g \rightarrow q\bar{q}$ splitting function over the initial energy density, which is valid at top collider energies, even when $\mu_B = 0$. The ICCING algorithm includes fluctuations in the gluon longitudinal momenta, a structure that supports the implementation of dynamical processes, and the c++ version is now open-source. There is significant strangeness production that reflects a different geometry than the bulk and could lead to the extraction of information about the hot spots of the medium.
[1] Patrick Carzon, Et al. arXiv: 1911.12454 [nucl-th] (Accepted by PRC)
We present a novel framework ebe-DREENA, based on a state-of-the-art dynamical energy loss model, which can include any temperature profile from bulk medium simulations. The framework is fully optimized to exploit different state-of-the-art medium evolutions - both event-by-event hydrodynamics and kinetic transport theory. It does not use fitting parameters within the energy loss model, allowing it to fully exploit differences in temperature profiles, as the only input in the framework. The framework applies to both light and heavy flavor observables, and both large (A+A) and small (e.g. p+A) systems. We calculate high-pt harmonics up to 6th order and exploit how the differences in the temperature profiles affect them, which will be especially useful with the upcoming high-luminosity measurements at RHIC and LHC. These comparisons of predictions and data are done within the same formalism and parameter set. We, therefore, propose ebe-DREENA as a unique tomography tool, which allows systematic and comprehensive mapping of QGP properties.
We study the interaction of leading jet partons in a strongly interacting quark-gluon plasma (sQGP) medium based on the effective dynamical quasi-particle model (DQPM). The DQPM describes the non-perturbative nature of the sQGP at finite temperature $T$ and baryon chemical potential $\mu_B$ based on a propagator representation of massive off-shell partons (quarks and gluons) whose properties (characterized by spectral functions with $T,\mu_B$ dependent masses and widths) are adjusted to reproduce the lQCD EoS for the QGP in thermodynamic equilibrium. We present the results for the jet transport coefficients, i.e. the transverse momentum transfer squared per unit length $\hat{q}$, the drag coefficient $\mathcal{A}$ as well as the energy loss per unit length $\Delta E =dE/dx$, in the QGP and investigate their dependence on the temperature $T$ and baryon chemical potential $\mu_B$ as well as on jet properties such as the leading jet parton momentum, mass, flavor, and the choice of the strong coupling constant. Firstly, the elastic scattering processes of a leading jet parton with the sQGP partons are explored discarding the radiative processes (such as gluon Bremsstrahlung) which are expected to be suppressed for the emission of massive gluons. Then we compute the cross sections and transport coefficients for radiative processes as well and compare the contributions from elastic partonic scattering and radiative processes for the emission of massive gluons.
We also present a comparison of our results for the elastic energy loss in the sQGP medium with the pQCD results obtained by the BAMPS model as well as with other theoretical approaches such as lattice QCD and the LBT model and also with estimates of $\hat q$ by the JET and JETSCAPE Collaborations based on a comparison of hydrodynamical calculations with experimental heavy-ion data.
Hadronic transport models are central approaches to study strangeness production from hadron interactions at low-beam energies.
At these energies, results from ArKCl and pNb collisions sparked interest in the last years, since much higher yields of double-strange hadrons were observed than theoretically expected. Therefore, in this work, a previously suggested mechanism to produce $\phi$ and $\Xi$ hadrons via rare decays of high mass $N^*$ resonances is explored with the transport approach SMASH[^1]. This mechanism is able to reproduce the available experimental data for $\phi$ and $\Xi$ with only one free parameter. Predictions for upcoming data for AgAg reactions at $E_{\rm Kin}=1.58A$ GeV from HADES will allow to further constrain this approach. The predicted particle yields include complementary strangeness production of the more abundant $K$ and $\Lambda + \Sigma^0$.
The high densities at these lower beam energies allow for multi-particle interaction as another class of reactions, also relevant for the production of (multi-)strange hadrons. Multi-particle reactions have been recently successfully introduced for the employed transport approach SMASH[^2]. In this work, the relevance of different multi-particle reactions in nucleus-nucleus collisions is explored. They are found to significantly impact particle abundances. In particular, the relevance of $B\bar{B}$ regeneration reactions is a controversy discussed topic ("proton anomaly"). It is demonstrated that, when including the $5\pi\rightarrow p\bar{p}$ regeneration reaction in the transport calculation, half of the (anti-)proton yield that is lost due to annihilations is recovered at mid-rapidity[^3]. By showing such sizable contributions, the findings motivate further exploration of multi-particle interaction in the strangeness sector.
[^1]: JS, , N. Kübler & H. Elfner, Phys. Rev. C 103, 044904 (2021)
[^2]: JS, D. Oliinychenko, J. M. Torres-Rincon & H. Elfner, Phys. Rev. C 104, 034908 (2021)
[^3]: O. Garcia-Montero, JS, A. Schäfer, J. M. Torres-Rincon & H. Elfner, arXiv:2107.08812
Strangeness production has been suggested as a sensitive probe to the early-time dynamics of the deconfined matter created in heavy-ion collisions. The ratios of particle yields involving strange particles are often utilized to study various properties of the created nuclear matter, such as the strangeness chemical potential and the chemical freeze-out temperature. Analysis of $d$+Au data will serve for connecting data between Au+Au and $p$+$p$ collisions and supply the baseline for the study of strangeness enhancement in the deconfined matter. The study of nuclear modification factor in $d$+Au collisions can also help to understand Cronin-like effects.
In this poster, we will present new measurements of mid-rapidity strange particle production ($K{_S}{^0}$, $\Lambda$, $\Xi$, $\Omega$) from $d$+Au collisions at $\sqrt{s_{\rm{NN}}} =$ 200 GeV recorded by the STAR experiment in 2016. We will report their transverse momentum spectra, dN/dy, average transverse momentum, yield ratios, and nuclear modification factors. The physics implications on the collision dynamics will be discussed.
Through analytical arguments, numerical calculations and comparison with experimental data, we demonstrate that the ratio of high-$p_{\perp}$ observables $v_2/(1−R_{AA})$ reaches a well-defined saturation value at high $p_{\perp}$, which depends on the spatial anisotropy of quark-gluon plasma formed in ultrarelativistic heavy ion collisions. By using our recently developed DREENA framework, which can accommodate any temperature profile, we calculate this ratio for various temperature evolutions and demonstrate that it is robustly related to the time-averaged anisotropy of the evolving QGP, as seen by jets. With the future reduction of experimental errors, our method will provide a way to constrain an important bulk property of the medium – spatial anisotropy of QGP – directly from high-$p_{\perp} experimental data.
The study of nuclear matter over a wide range of collision energy is provided by the RHIC Beam Energy Scan (BES). One focus of the program, namely to locate the critical point (CP) in the QCD phase diagram, is closely tied to the measurement of kurtosis in net-proton multiplicity distribution as a function of $\sqrt{s_{NN}}$. Previous results from BES-I obtained with 3.1$\sigma$ significance motivated us to increase the statistics and to extend the collision energy down to $\sqrt{s_{NN}}=3.0$ GeV in the BES-II.
The event-by-event fluctuations in net-lambda multiplicity distribution for the first BES showed that the cumulant ratios have a similar energy and multiplicity dependence compared to those for protons, and the observed deviation from Poisson baseline can be attributed to baryon number and strangeness conservations. It is also known from the previous work that the derived freeze-out parameters show sensitivity to the quark content of the hadrons, implying a quark mass dependence in the process of hadronization. We present in this poster, the lambda fluctuation analysis in Au+Au collisions at the lowest collision energy ($\sqrt{s_{NN}}=3.0$ GeV), where we continue the comparison with proton fluctuations and analyze the behaviour of both baryons, specifically in terms of their difference in quark content and applicable conservation laws.
Using 3-fluid dynamical (3FD) model and microscopic transport model UrQMD,
we made predictions for the global polarization of Λ and anti-Λ hyperons
in Au+Au and Ag+Ag collisions at moderately relativistic collision
energies of √(s_NN ) = 2.4−11 GeV. The dependence of the polarization on
the centrality of the collision, as well as on the rapidity and transverse
momentum, is studied. The obtained results agree well with the available
experimental data. The polarization is predicted to reach a maximum or
plateau (depending on the equation of state and centrality) at
√(s_NN) ≈ 3 GeV. It is found that the global polarization increases with
increasing width of the rapidity interval in the central rapidity region.
The global polarization Λ and anti-Λ, originated from axial vortex effect
(AVE), was also calculated within the 3FD model. It is found that the
equation of state with the deconfinement transition leads to splitting in
polarization of Λ and anti-Λ in good agreement with the STAR data.
We consider the experimental data on yields of protons, strange Λ’s, and multistrange baryons (Ξ, Ω), and antibaryons production on nuclear targets, and the experimental ratios of multistrange to strange antibaryon production, at the energy region from SPS up to LHC, and compare them to the results of the Quark-Gluon String Model calculations. In the case of heavy nucleus collisions, the experimental dependence of the Ξ+/Λ, and, in particular, of the Ω+/Λ ratios, on the centrality of the collision, shows a manifest violation of quark combinatorial rules.
Extremely large angular orbital momentum can be produced in non-central heavy-ion collisions, leading to a strong transverse polarization of partons that scatter through the quark-gluon plasma (QGP) due to spin-orbital coupling. To understand the hyperon polarization observed in relativistic nuclear collisions, we develop a microscopic approach to describe the formation and space-time evolution of quark polarization inside the QGP. Production of polarization both from the initial hard scatterings and during the QGP expansion have been consistently described using the quark-potential scattering approach, which has been coupled to realistic initial condition calculation and the subsequent (3+1)-dimensional viscous hydrodynamic simulation of the QGP for the first time. Within this improved approach, we have found that different rapidity-dependent initial energy density distributions generate different time evolution profiles of the longitudinal flow velocity gradient of the QGP, which further lead to an approximately 15% difference in the final polarization of quarks collected on the hadronization hypersurface of the QGP. Therefore, in addition to the collective flow coefficients, the hyperon polarization could serve as a novel tool to help constrain the initial condition of the hot nuclear matter created in high-energy nuclear collisions.
We have proposed a mechanism for Xi baryon production in proton-nucleus collisions in which hyperon resonances and anisotropic hyperon production played a role. Parameters of the model were chosen to account for the observed Xi multiplicity by the HADES collaboration (GSI, Darmstadt) in sub-threshold p+Nb collisions. [1] In the present contribution, we investigate whether a similar mechanism can explain the high Xi yield found by HADES in Ar+KCl collisions at \sqrt{s_{NN}}=2.61 GeV.
[1] M. Zétényi, Gy. Wolf, Phys. Lett. B 785 (2018) 226-231.
Relativistic heavy-ion collisions provide a unique opportunity to study the properties of strongly interacting matter under extreme conditions. Search for the QCD critical point and the onset of deconfinement is the main motivation of the beam energy scan (BES) program at RHIC. Strangeness (especially the multi-strangeness) production has been suggested as a sensitive probe to the early dynamics of the deconfined matter created in heavy-ion collisions. The data taken during 2010 and 2011 in BES phase-I, have indicated the potential changes of medium properties in between $\sqrt{s_{NN}}$ = 19.6 GeV and 11.5 GeV. However, the statistics collected during the BES phase-I are not enough to draw definite conclusions. Since 2018, STAR has conducted the BES phase-II program and accumulated high statistics Au+Au collisions data at various energies ($\sqrt{s_{NN}}$) below 27 GeV. The productions of $K_{s}^{0}$, $\Lambda$, $\Xi$, $\Omega$, and $\phi$ from Au+Au collisions at $\sqrt{s_{NN}}$ = 27, 19.6, and 14.5 GeV will be presented in this talk. The strange hadron spectra, nuclear modification factors, and particle ratios (in particular $\Omega$/$\phi$) will be reported. The physics implications on the collision dynamics will also be discussed.
Exploring the QCD phase diagram and searching for the QCD critical point are some of the main goals of Beam Energy Scan (BES-I) program at RHIC. In 2017, as a continuation to BES-I, the STAR experiment collected large datasets of Au+Au collisions at $\sqrt{s_{NN}} =$ 54.4 GeV. The identified particle spectra and yields provide information about the bulk properties of the medium. The centrality dependence of the freeze-out parameters provides an opportunity to enlarge the (T, $\mu_B$) region of the phase diagram to search for the QCD critical point.
We present the measurements of identified charged particle spectra of $\pi^\pm$, $K{^\pm}$, $p$, and $\bar{p}$ at midrapidity $|y|\leq 0.1$. The results for the transverse momentum spectra, particle yields dN/dy, average transverse momentum $\langle$p$_{T}$$\rangle$, and particle ratios will be presented for different centrality classes and compared with AMPT and HIJING model calculations. In addition, the extracted freeze-out parameters will be compared with the previously published results. The physics implications of the results will be discussed.
We investigate the masses and radii of neutron stars within the framework of the in-medium modified chiral soliton model, considering the effects of surrounding baryonic environment on the properties of in-medium baryons. The equation of state describing an infinite and asymmetric nuclear matter are obtained by introducing the density-dependent functions. To extrapolate the high density and highly isospin asymmetric region, we study the masses and radii of neutron stars. The results predict the masses and radii to be ~1.4$M_{\bigodot}$ and ~2$M_{\bigodot}$, respectively. We discuss the physical meaning of the equation of state obtained from the chiral solitonic approach, based on the present results.
We propose that the yield ratio of free spectator neutrons produced in ultracentral $^{96}$Zr+$^{96}$Zr to $^{96}$Ru+$^{96}$Ru collisions is a robust probe of the neutron-skin thickness $\Delta r_{\mathrm{np}}$ and the slope parameter $L$ of the symmetry energy. The idea is demonstrated based on the proton and neutron density distributions of colliding nuclei from the Skyrme-Hartree-Fock model, and a Glauber model that provides information of spectator matter, where free neutrons are produced from the deexcitation of heavy clusters through the GEMINI model and direct ones that have not coalesced into light clusters through a Wigner function approach. A larger $\Delta r_{\mathrm{np}}$ associated with a larger $L$ value increases the isospin asymmetry of spectator matter and thus leads to more free neutrons, especially in ultracentral collisions where the multiplicity of free neutrons are not affected by uncertainties of cluster formation and deexcitation. The ratio of neutron multiplicities in isobaric collision systems reduces the theoretical and experimental uncertainties, and is insensitive to the nuclear deformation effects.
Gauge fields provide the fundamental interactions in the Standard Model of particle physics. Gauge field configurations with nontrivial topological windings are known to play crucial roles in many important phenomena, from matter-anti-matter asymmetry of today's universe and the permanent quark confinement to topological phases in condensed matter. Their presence is however elusive for direct detection in experiments. It turns out that measurements of the so-called chiral magnetic effect (CME) can be used to access and manifest gauge field topology in quantum chromo matter created by heavy ion collisions. The CME is a nontrivial macroscopic transport phenomena arising from microscopic quantum anomaly of underlying fermions in a chiral material (e.g. a Dirac/Weyl semimetal or a quark-gluon plasma), which has been in the spotlight lately across different disciplines of physics. Potential discovery of CME in heavy ion collisions is of utmost significance, with extensive experimental searches carried out over the past decade. In particular a dedicated experiment of isobar collisions was performed and the first set of blind analysis results were publicly released in late 2021 based an amazingly large data sample of about 2 billion events. Such data have already shown unprecedented precision in CME-motivated correlation measurements, whose interpretation however has so far been complicated by the difference in the bulk matter properties such as multiplicity and elliptic flow between the isobar systems. In this talk, we report our recent efforts to address such pressing issue and discuss our progress in understanding these isobar data. In particular, three aspects will be presented: (1) the event-by-event anomalous-viscous fluid dynamics (EBE-AVFD) as an essential tool for CME modeling and its application for characterizing various observables’ responses to CME signals as well as backgrounds; (2) the quantitative description of the multiplicity and flow difference between isobar systems and the sensitivity to their respective nuclear geometry inputs (in particular the neutron skin and shape deformations); (3) the identification of a new baseline of CME observables for the isobar comparison after taking into account the above known bulk differences as well as an attempt to extract/constrain CME signals in isobar collisions. References: PRL125(2020)242301; Nature Reviews Physics 3(2021)55-63; arXiv:2106.10847; PRC104(2021)064906; CPC46(2022)014101.
It is known that 1+1 dimensional real scalar models with a negative mass squared have a soliton solution called the kink. We analyze the distribution of the energy-momentum tensor around the kink by incorporating the quantum correction up to leading order. The Fourier transform of the distribution corresponds to the gravitational form factors. We employ the collective coordinate method which deals with the soliton's coordinate as a dynamical variable. The zero mode that gives rise to the infrared divergence is eliminated in this method. The ultraviolet divergences in the quantum correction are removed by the vacuum subtraction with the prescription called the mode-number cutoff and the mass renormalization. We obtain the result consistent with the energy-momentum conservation. The spatial integral of the energy density agrees with the known result on the total energy of the soliton.
The fundamental and first two lowest-frequency excited modes of radial oscillation have been computed in the high nuclear density regime for a set of seven realistic equations of state (EoS) as functions of central energy density. Various types of zero-temperature EoS of cold nucleonic, hyperonic, and strange-quark matter models are used in the inner core to determine the internal structure in and around the hydrostatic equilibrium states and investigate the influence of each EoS on the dynamical behavior of non-rotating neutron stars. We confirm the principal results of earlier, related studies that suggest an underlying correlation between the frequency spectrum of the fundamental oscillation mode and the variation of the adiabatic index over the high nuclear-density regime. We provide valuable information to impose further constraints on the plausible set of realistic EoS models, in addition to the practical applications for the rapidly evolving field of asteroseismology of compact objects.
The magnetic field seems to play a significant role in shaping and working the visible universe. It gives rise to a lot of non-trivial and anomalous behavior in the system in which they are present, extending from the effects seen in condensed matter physics in Dirac and Weyl semi-metals to large cosmological objects like in neutron stars or black holes. The strength of the magnetic field in natural systems can be as low as $10^{-5}$T for that of the Earth to as high as $10^{11}$ T in the Magnetars. But the strongest magnetic field on the Earth is manmade and is produced in high-energy heavy-ion collision experiments at RHIC or LHC. The magnitude of the magnetic field produced here is 3 to 4 orders larger than that produced in Magnetars[1]. In a heavy-ion collision, a strongly coupled Quark-Gluon Plasma(QGP) is formed and its space-time evolution can be described using viscous hydrodynamics formulation. The presence of a strong transient electromagnetic field in the initial stages of heavy-ion collisions indicates that the dynamics of the QGP can be better understood using the RMHD (Relativistic Magnetohydrodynamics) formulation. The RMHD framework describes the system of any relativistic charged fluid and its interaction with the electromagnetic field and the governing laws for fluid and electromagnetic fields need to be solved in a self-consistent manner. There are a few underlying microscopic theories by which these studies can be done; the kinetic theory is one of them. In our current work[2,3], we use the relativistic Boltzmann equation in the relaxation time approximation for the collision kernel. Here, we have formulated the second-order causal evolution equations for the viscous stresses, e.g., bulk, diffusion, and shear stresses, along with the calculation of relevant transport coefficients for both ideal and resistive MHD. We have also computed anisotropic components of the electrical conductivity. These formulations can serve as an input to numerical studies. Last but not least, we have given $\delta f$ (slight deviation from the equilibrium distribution function), which can be readily applied to the Cooper-Frye prescription for calculating particle spectra in phenomenological studies.
1.{Event-by-event fluctuations of magnetic and electric fields in heavy ion collisions},Bzdak, Adam and Skokov, Vladimir.
2. {"Relativistic resistive dissipative magnetohydrodynamics from the relaxation time approximation"}, Panda, Ankit Kumar and Dash, Ashutosh and Biswas, Rajesh and Roy, Victor,
3."Relativistic non-resistive viscous magnetohydrodynamics from the kinetic theory: a relaxation time approach",
Panda, Ankit Kumar and Dash, Ashutosh and Biswas, Rajesh and Roy, Victor,
Hadronization is a non-perturbative process, which theoretical description can not be deduced from first principles. Modeling hadron formation, requires several assumptions and various phenomenological approaches. Utilizing state-of-the-art Computer Vision and Deep Learning algorithms, it is eventually possible to train neural networks to learn non-linear and non-perturbative features of the physical processes.
Here, I would like to present the results of two deep neural networks, by investigating global and kinematical quantities, indeed jet- and event-shape variables. The widely used Lund string fragmentation model is applied as a baseline in √s=7 TeV proton-proton collisions to predict the most relevant observables at further LHC energies. Non-liear QCD scaling properties were also identified and validated by experimental data.
Global, pT-integrated polarization of Lambda hyperons in heavy-ion collisions is described well in hydrodynamic and transport models. However, a proper description of the azimuthal angle dependence of Lambda polarization remains a puzzle. Recently introduced spin-shear coupling improves the agreement with the experiment, which is still far from being satisfactory.
In this contribution, we present both the global and local Lambda polarization in Au+Au collisions at sqrt(s) = 200 and 27 GeV computed using a 3+1-dimensional viscous hydrodynamic model (vHLLE) with 3D Monte Carlo Glauber and SMASH initial states. We discuss the initial state dependence of the local polarization and conclude which one works better for both the global and local polarization measured at sqrt(s) = 200 and 27 GeV. We also provide predictions for the polarization signal in asymmetric Pb+W, Pb+Ti and Pb+C collisions in a proposed fixed-target experiment at LHC at sqrt(s) = 72 GeV.
The measurement of spin polarization of particles emitted in heavy-ion collisions has opened the possibility for new phenomenological investigations of spin physics in relativistic fluids. This motivates the development of hydrodynamic with spin degrees of freedom. One of the features of this theory is that different choices of the decomposition of orbital and spin angular momentum might give different descriptions. In this talk, I will discuss how observables in a relativistic fluid at local thermal equilibrium are affected by the choice of the stress-energy tensor and the spin tensor. In particular, I will discuss how the predictions of the spin polarization vector of spin 1/2 particles changes in different pseudo-gauges.
1 M. Buzzegoli, arXiv:2109.12084
We derive a quantum kinetic theory for QED based on Kadanoff-Baym equation[1]. By assuming parity invariance and considering a complete set of self-energy diagrams, we find the resulting kinetic theory expanded to lowest order in $\hbar$ generalizes the well-known classical kinetic theory to massive case. It contains elastic and inelastic collision terms and integrates screening effect naturally. We also discuss generalization to QCD. The approach allows us to study complete collisional contribution to spin polarization in heavy ion collisions. We find a new collisional contribution to shear-induced spin polarization, which is not suppressed compared to contributions already included in current phenomenological studies. It may shed light on the spin polarization puzzle.
[1]Shu Lin, "Quantum Kinetic Theory for Quantum Electrodynamics" arxiv:2109.00184.
We explore the ability of a recently proposed jet substructure technique, Dynamical Grooming, to pin down the properties of the Quark-Gluon Plasma formed in ultra-relativistic heavy-ion collisions. In particular, we compute, both analytically and via Monte-Carlo simulations, the opening angle $\theta_g$ of the hardest splitting in the jet as defined by Dynamical Grooming. Our calculation, grounded in perturbative QCD, accounts for the factorization in time between vacuum-like and medium-induced processes in the double logarithmic approximation. We observe that the dominating scale in the $\theta_g$-distribution is the decoherence angle $\theta_c$ which characterises the resolution power of the medium to propagating color probes. This feature also persists in strong coupling models for jet quenching. We further propose for potential experimental measurements a suitable combination of the Dynamical Grooming condition and the jet radius that leads to a pQCD dominated observable with a very small sensitivity (≤10%) to medium response.
References:
[1] P. Caucal, A. Soto-Ontoso and A. Takacs, arXiv:2111.14768
[2] P. Caucal, A. Soto-Ontoso and A. Takacs, JHEP, 20 (2021)
We propose an observable counting a weighted difference between right-handed and left-handed lepton pairs, which is coined dilepton helical rate. The weight is the momentum difference of the lepton pairs projected onto an auxiliary vector. We derive the helical rate in a quark-gluon plasma with a vorticity in the limit when the quark and lepton masses are ignored. We find the helical rate is maximized when the auxiliary vector is parallel to the vorticity, in which case it has a nearly spherical oblate ellipsoidal distribution. We also propose that dilepton helical rate can be used as a vortical-meter for quark-gluon plasma.
The detection of cosmic-ray antinuclei is a potential breakthrough approach for the identification of dark matter. Dominant sources of antinuclei in the astrophysical background are proton-proton interactions. Typically, a process producing heavier antinuclei will also produce antiprotons. Therefore, the antiproton production constrains the other antinuclei when assuming specific parameters for antinuclei formation, and needs to be measured with high precision. The production of light (anti)nuclei (e.g. deuterons) in hadronic interactions is described by different models (coalescence, thermal model etc.), which are also not well understood. A better understanding of these mechanisms is needed, which motivates the effort to analyze large data sets from fixed-target experiments.
The NA61/SPS Heavy Ion and Neutrino Experiment (NA61/SHINE) is a fixed-target experiment at the CERN Super Proton Synchrotron, which studies hadron production in hadron-nucleus and nucleus-nucleus collisions for various physics goals. This talk will present the new preliminary measurements of π±, K±, proton and antiproton spectra using the high-statistics proton-proton data sets from NA61/SHINE. The new spectra cover a larger phase space in rapidity and transverse momentum, and will be compared to previous results from NA61/SHINE, as well as to predictions of current models. Efforts to measure the deuteron production will also be discussed.
The understanding of the mechanisms for the production of weakly bound clusters, such as a deuteron $d$, in heavy-ion reactions at midrapidity is presently one of the challenging problems which is also known as the "ice in a fire" puzzle.
In this study we investigate and compare two main mechanisms for the deuteron production based on the Parton-Hadron-Quantum-Molecular Dynamics (PHQMD) [1] microscopic transport approach: the so-called "kinetic mechanism" for the deuteron production (and disintegration) by hadronic reactions via pion or nucleon catalysis as well as the formation of deuterons by a potential interactions between nucleons.
The "kinetic mechanism" is realized by the implementation of the dominant inelastic reactions for deuteron production in the PHQMD, i.e. $\pi NN\leftrightarrow \pi d$, $NNN\leftrightarrow N d$ and $NN \leftrightarrow d \pi$, based on the covariant rate formalism [3] for $3 \leftrightarrow 2$ reactions obeying the detailed balance.
Differently to other studies [4], we accounted for the quantum origin of the deuteron as elongated object with a radius of $r_d \sim 1.8$ fm, while in semi-classical transport approaches, realized within a test particle method, the deuteron is treated as a point like particle. The final size effect has been modelled by the "excluded-volume" (defined to the physical radius of the deuteron), which forbids the formation of deuteron in the presence of any hadrons within the deuteron radius $r_d$. The latter reduces substantially the deuteron production by the "kinetic mechanism" in the dense medium. Moreover, we take into account the full isospin decomposition of the various $\pi NN\leftrightarrow \pi d$, $NNN\leftrightarrow N d$ and $NN \leftrightarrow d \pi$ channels which is important due to the isospin asymmetry of Au+Au reactions.
The "potential" deuterons are identified in the PHQMD via Minimum Spanning Tree (MST) algorithm [2] which is used to recognize the formation of clusters due to the potential interaction of baryons during the dynamical evolution of the fireball.
The final results including deuterons, produced by the both mechanisms, provide a good description of the available measurements for deuterons at mid-rapidity from SIS to the RHIC energies and provide useful predictions for the upcoming CBM FAIR experiment.
References:
[1] J. Aichelin, E. Bratkovskaya, A. Le Fevre, V. Kireyeu, V. Kolesnikov, Y. Leifels, V. Voronyuk and G. Coci, Phys. Rev. C 101 (2020) no.4, 044905.
[2] S. Gläßel, V. Kireyeu, V. Voronyuk, J. Aichelin, C. Blume, E. Bratkovskaya, G. Coci, V. Kolesnikov and M. Winn, Phys. Rev. C 105 (2022) no.1, 014908.
[3] W. Cassing, Nucl. Phys. A 700, 618-646 (2002).
[4] J. Staudenmaier, D. Oliinychenko, J. M. Torres-Rincon and H. Elfner, Phys. Rev. C 104 (2021) no.3, 034908.
While the $\phi$ meson vacuum properties, such as mass and width, are well known,
it is not clear how these properties will change once it is put in a dense
environment such as nuclear matter.
Theoretically, many works have been conducted with the aim of studying the $\phi$
meson in nuclear matter. Connecting theoretical results with experimental
measurements is, however, not a trivial task, as the $\phi$ meson in nuclear matter is
usually produced in relatively high-energy pA reactions, which are generally
non-equilibrium processes.
In this presentation I will report on an ongoing project [1], attempting to simulate
pA reactions in which the $\phi$ meson is produced in nuclei, making use
of a transport approach [2]. Results of simulations of 12 GeV/30 GeV p+C and p+Cu
reactions will be presented and comparisons between obtained dilepton spectra
and experimental data of the E325 experiment at KEK [3] will be made.
Furthermore, predictions for the ongoing J-PARC E16 experiment [4] for both
dilepton and $K^+K^-$ spectra will be given and discussed.
[1] P. Gubler and E. Bratkovskaya, in progress.
[2] W. Cassing and E.L. Bratkovskaya, Nucl. Phys. A 831, 215 (2009).
[3] R. Muto et al., Phys. Rev. Lett. 98, 042501 (2007).
[4] S. Ashikaga et al., (J-PARC E16 Collaboration), JPS Conf. Proc. 26, 024005 (2019).
We investigate the axial-vector meson $h_1$. We coupled 4 channel, $\pi\rho$, $\eta\omega$, $K\bar{K}^*$ and $\eta\phi$, which generate two resonance structure within energy up to 600 MeV above the threshold. Moreover, having reproduced the experimental data of charge exchange reaction ($\pi p\to 3\pi n$), we extract the pole position and residue of each resonance and identify them as the existing $h_1$(1170) and $h_1$(1380) resonances. We discuss the nature of these resonances and their internal structures.
The NA61/SHINE experimental physics program focuses on searching for the critical point and studying the properties of the onset of deconfinement in the strongly interacting matter. A two-dimensional scan is performed by varying the beam momentum (from 13$A$ to 150/158$A$ GeV/$c$) and the system size (from p+p to Pb+Pb) of the collided nuclei. This contribution presents results on $K^*(892)^0$ and $\phi (1020)$ meson production in proton-proton collisions, the smallest system in the scan, at beam momenta of 40 and 80 GeV/$c$, and most detailed ever experimental data at 158 GeV/$c$.
The analysis of short-lived resonances may allow understanding the less-known aspects of high energy collisions, especially their time evolution. The yields of resonances may help to distinguish between two possible freeze-out scenarios: sudden and gradual. In particular, the ratio of $K^{*}/K$ production allows estimating the time interval between chemical (end of inelastic collisions) and kinetic (end of elastic collisions) freeze-outs.
Strangeness production enhancement in large systems compared to small ones is traditionally considered as a signal of quark-gluon plasma formation. To discuss the nature of the enhancement it is important to compare this effect in both the open and hidden strangeness sector which is done in this contribution. The comparison of $\phi (1020)$ meson production in p+p and Pb + Pb collisions shows also a non-trivial system size dependence of the longitudinal evolution of hidden strangeness production, contrasting with that of other mesons.
In detail, this talk will include the measurements of rapidity, transverse momentum, and transverse mass spectra of $K^{*}(892)^{0}$ and $\phi (1020)$, which will be compared to model predictions (such as EPOS, Pythia, and UrQMD). The multiplicity of studied hadrons and the ratio of $\langle K^{*}(892)^{0} \rangle$/$\langle K\pm \rangle$ and $\langle \phi \rangle$/$\langle \pi \rangle$ as a function of system size and energy are planned to be presented together with the results from other experiments. For $K^{*}(892)^{0}$, the results will also include the measured mass and width of $K^{*}(892)^{0}$ as a function of transverse momentum. For $\phi (1020)$, the width of rapidity distribution will be presented based on the NA61/SHINE p+p data and the world data on nucleus-nucleus collisions.
Hadronic resonances are effective tools for studying the hadronic phase in ultra-relativistic heavy-ion collisions. In fact, their lifetime is comparable to the hadronic phase and resonances are sensitive to the hadronic phase effects such as rescattering and regeneration processes which might affect the resonance yields and shape of the transverse momentum spectra. $\Lambda(1520)$ has a lifetime of around 13 fm/$\it{c}$, which lies in between the lifetimes of $K^*$ and $\phi$ resonances. The resonance to stable particle yield ratios can be used to study the properties of the hadronic phase. Recently, ALICE observed the suppression of the $\Lambda(1520)/\Lambda$ ratio in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV as a function of centrality. It is therefore interesting to investigate the multiplicity-dependent study of $\Lambda(1520)/\Lambda$ ratio for pp collisions, since this can serve as a baseline for heavy-ion collisions.
In this contribution, we present new results on the measurement of the baryonic resonance $\Lambda(1520)$ as a function of the charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV. The transverse momentum spectrum, the integrated yield $(\rm d \it N/ \rm d \it y )$, the mean transverse momentum $(\langle p_{\rm{T}}\rangle)$ and the $ \Lambda(1520)/\Lambda$ yield ratio will be presented as a function of the charged-particle multiplicity.
Short-lived resonances can probe strongly interacting matter produced in high-energy heavy-ion collisions. In particular, K(892)$^{\mathbf{\pm}}$ is important because of its very short lifetime (around 4 fm/c), which is comparable to the partonic plasma phase. Also, its short lifetime can be used to study the rescattering and regeneration effect in the hadronic phase. An event shape observable like transverse spherocity is sensitive to hard and soft processes. Such an observable can be used as a tool to disentangle pp collisions into isotropic (dominated by soft QCD) and jetty (dominated by hard QCD) events. In this work, we present the latest developments in K(892)$^{\mathbf{\pm}}$ analysis as a function of event multiplicity and transverse spherocity exploiting pp collisions at $\sqrt{s}$ = 13 TeV collected by ALICE. The results obtained in this analysis will be compared to those obtained for other soft particles and the $\it{p}_{T}$-differential ratio of K*(892)$^{\mathbf{\pm}}$ yields to those of long-lived stable hadrons in the same multiplicity and transverse spherocity intervals will also be presented.
Short-lived resonances can probe strongly interacting matter produced in high-energy heavy-ion collisions. The K*(892)± resonance is particularly interesting because of its very short lifetime (~4 fm/c), comparable to that of the hadronic phase. Therefore, it may be sensitive to the competing rescattering and regeneration mechanisms, which modify the particle's momentum distributions after hadronization. In this poster, recent measurements of resonance production in proton-proton (pp) collisions as a function of event multiplicity will be presented, exploiting the large sample of pp collisions at $\sqrt(s)$ = 13 TeV collected by ALICE. These measurements show the onset of phenomena typical of heavy-ion collisions, like collective behaviour and suppression of the yield ratios of short-lived resonances to stable particles with increasing multiplicity.
Short-lived hadronic resonances are very useful to probe the late-stage evolution of ultra-relativistic heavy-ion collisions. Since their lifetimes are comparable to the hadronic phase timespan, their measured yields are modified via rescattering and regeneration processes. The suppression of the K$^{*0}$/K ratio in central Pb--Pb collisions compared to pp interactions already hints at the dominance of rescattering effects over regeneration effects in the hadronic phase. The mass, lifetime and quark content of K$^{*\pm}$ are comparable to those of K$^{*0}$. Hence, systematic measurements of K$^{*0}$ and K$^{*\pm}$ enable us to investigate further the dynamics of the hadronic phase, to study its lifetime and to probe in-medium parton energy loss with high $p_{\mathrm{T}}$ resonances.
We report on the first measurement of K$^{*\pm}$ production in midrapidity for Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. The results include the transverse momentum spectra, integrated yields, mean transverse momenta, particle yield ratios, and nuclear modification factor as a function of charged-particle multiplicity. These results will be compared with published K$^{*0}$ measurements at the same energy.
Including the finite nuclear thickness has been shown to significantly affect the calculated energy density $\epsilon(t)$ [1] from the primary collisions of heavy ions at moderate or low energies. As a result, the peak density reached during the collisions can be much lower than the predicted initial density from the Bjorken formula. Recently we have extended the model to also calculate the conserved-charge $(B,Q,S)$ densities from the primary collisions, which then allowed us to extract the time dependence of the temperature $T$ and chemical potentials $\mu$ of the matter produced in central Au+Au collisions [2].
In this talk, I will discuss our semi-analytical model of the initial production that includes the nuclear thickness effect. I will first show our results of $\epsilon(t)$, $n_B(t)$, $n_Q(t)$, and $n_S(t)$ in comparison with those predicted by the Bjorken model. Next, I will show the extracted $T(t)$, $\mu_B(t)$, $\mu_Q(t)$, and $\mu_S(t)$ for a QGP using quantum statistics and Boltzmann statistics. Then, I will present our results on the $T-\mu_B$ trajectories, highlighting how they depend on the chosen statistics and parton formation time $\tau_F$ in relation to the possible location of the critical end point (CEP). I will also show that the strangeness neutrality $n_S(t)=0$ leads to the relation $\mu_B(t)-\mu_Q(t)-3\mu_S(t)=0$, and that the assumption of $\mu_Q(t)=0$ with $\mu_S(t)=\mu_B(t)/3$ is appropriate to simplify the mapping between densities and $T-\mu$ values. Finally, I will show the effect of transverse expansion on the event trajectories and also compare with trajectories of isentropic expansion that are obtained with lattice QCD equation of state.
References
[1] T. Mendenhall and Z. W. Lin, Phys. Rev. C 103 024907 (2021).
[2] T. Mendenhall and Z. W. Lin, arXiv:2111.13932 [nucl-th].
The polarization of the $\Lambda$ hyperon has become an important probe of the Quark-Gluon Plasma produced in relativistic heavy-ion collisions. Recently, it has been found that polarization receives a substantial contribution from a local equilibrium term proportional to the symmetric derivative of the four-temperature vector, the thermal shear tensor. We show that, at very high energies, this term can restore the agreement between the experimental measurements and the predictions of the hydrodynamic model, provided that the hadronization hypersurface is isothermal. We review the theoretical derivation of this new term, discuss numerical computations at RHIC and LHC energies, and compare them with the experimental data. We also present the effect of feed-down corrections.
Based on refs. [1,2,3]
[1] Becattini, Buzzegoli, Palermo,Phys.Lett.B 820 (2021) 136519
[2] Becattini, Buzzegoli, Palermo, Inghirami, Karpenko, Phys. Rev. Lett. 127 (2021) 272302
[3] Karpenko, Palermo, Becattini, in preparation.
In this talk we present a resummation of the QCD equation of state from
lattice simulations at imaginary chemical potentials. We utilize a
generalization of the scheme introduced in 2102.06660, moving to the case of
non-zero strangeness chemical potential. We present continuum extrapolated
results for thermodynamic observables in the temperature range
130 MeV $\le T \le$ 280 MeV, for chemical potentials up to $\mu_B/T=3.5$,
along the stangeness neutral line. We also extrapolate beyond
strangeness neutrality to small values of the strangeness-to-baryon-number
ratio $R=n_S/n_B$.
The search for experimental signatures of the critical point (CP) of strongly interacting matter is one of the main objectives of the NA61/SHINE experiment at CERN SPS. One such candidate observable is local fluctuations of the proton density in transverse space, constituting an order parameter of the chiral phase transition, and expected to scale according to a universal power-law in the vicinity of the CP. Their scaling can be probed through an intermittency analysis of the proton second scaled factorial moments (SSFMs) in transverse momentum space. The first such analysis [1] revealed power-law behavior in NA49 Si+Si collisions at 158A GeV/$c$, the fitted power-law exponent being consistent with the theoretically expected critical value, within errors.
In the present talk, we propose a novel technique for conducting intermittency analysis, and explore its efficacy on the available NA61/SHINE collision systems (Be+Be, Ar+Sc, Pb+Pb). We discuss the experimental and methodological challenges posed by such an analysis, and apply a dedicated, new method of handling statistical and systematic uncertainties that solves several known problems of the standard intermittency analysis in the face of low to moderate event statistics. In particular, we present the outline of a Monte Carlo simulation scan used in assessing and weighing alternative models with critical and background components versus the experimental results, which would allow us to obtain reliable estimates and confidence intervals for the intermittency index (power-law exponent) $\phi_2$ compatible with the experimental data.
References:
[1] T. Anticic et al, Eur. Phys. J. C 75: 587 (2015).
The quark susceptibilities are a very useful tool to understand the nature
of the degrees of freedom in the vicinity of the QCD phase transition while Heavy-Quarks (HQs) transport coefficients give us information on their thermalization time in the Quark-Gluon Plasma (QGP). Recently, new lattice results for the equation of state of QCD with $2+1+1$ dynamical flavors have become available. Therefore, we extend our QPM approach for $N_f = 2+1$ to $N_f = 2+1+1$ where the charm quark is included. We also explore the extension of QPM approach to a more realistic model in which partonic propagators explicitly depend on the three-momentum with respect to the partonic matter at rest in order to match pQCD at high momenta following Dyson-Schwinger studies in the vacuum. In this context, we evaluate and correctly reproduce both EoS and quark susceptibilities which are understimated in the simple QPM approach. Therefore, we study the impact of the extended QPM approach on both the transport coefficient and the spatial diffusion coefficient $D_s$ of charm quark making a comparison with the results in the standard QPM approach. The $D_s$ for the extended QPM is modified when $T/T_c \le 2$ due to the enhancement of the $g(T)$ at low temperatures which corresponds to a decrease of the $D_s$ coefficient. This means that QPM describes a strong non-perturbative behaviour near to $T_c$ similar to the one achieved in strongly coupled theory as AdS/CFT while in the high T region the $D_s$ reaches the pQCD limit quickly than the standard QPM. An explicit treatment of the moment dependence of quasi-particle masses and coupling has been often postponed, but it significantly affects
the p dependence of $R_{AA}$,$v_2$, $v_3$. Given the new upgrade of ALICE and CMS will allow to access low $p_T$ obsevarbles with high precision,
the corresponding development of the QPM approach employed for realistic simulation is a necessary step toward a more solid and precise determination of $D_s$.\\
[1] M.L.Sambataro, S.Plumari and V.Greco, Eur. Phys. J. C 80, no.12, 1140 (2020).\
[2] M.L.Sambataro et al., in preparation.
After the successful installation and first operation of the upgraded Inner Tracking System (ITS2), which consists of about 10 m$^2$ of monolithic silicon pixel sensors, ALICE is pioneering the usage of bent, wafer-scale pixel sensors for the ITS3 for Run 4. Sensors larger than typical reticle sizes can be produced using the technique of stitching. At thicknesses of about 30 µm, the silicon is flexible enough to be bent to radii of the order of 1 cm. By cooling such sensors with a forced air flow, it becomes possible to construct truly cylindrical layers which consist practically only of the silicon sensors. The reduction of the material budget and the improved pointing resolution will allow new measurements, in particular of heavy-flavour decays and electromagnetic probes. In this presentation, we will report on the sensor developments, the performance of bent sensors in test beams, and the mechanical studies on truly cylindrical layers.
The NA60+ experiment, which has been proposed as a fixed target experiment at the CERN SPS, is designed to study the phase diagram of the strongly interacting matter at high baryochemical potential, μB 200-400 MeV. Its main goals will be focused on precision studies of thermal dimuons, heavy quark and strangeness production in Pb-Pb collisions at center-of-mass energies ranging from 5 to 17 GeV.
The proposed experimental apparatus will be composed of a vertex telescope located close to the target and a muon spectrometer located downstream of a hadron absorber. The vertex telescope will consist of several planes of ultra-thin, large area Monolithic Active Pixel Sensors (MAPS) embedded in a dipole magnetic field. The muon spectrometer will utilize large area gaseous detectors for muon tracking and a toroidal magnet based on a new light-weight and general-purpose concept.
Significant progress has been achieved in the R&D for the MAPS detectors of the vertex spectrometer, thanks to a common project with the ALICE ITS3, and towards the construction of prototypes (GEM, MWPC) for the muon tracker. A beam test for prototypes is foreseen at the end of 2022 at SPS. Furthermore, a working prototype of the toroidal magnet of the muon spectrometer (scale 1:5) was built and tested, and an experimental zone on the beam line H8 of the SPS was singled out for the experiment, after detailed integration and radioprotection studies. A Letter of Intent is in preparation and will be submitted in 2022, and the experiment aims at taking data after LHC Long Shutdown 3.
An ambitious physics program is foreseen, which includes the measurement of the yield and elliptic flow of thermal dimuons, the search for chiral symmetry restoration effects through the ρ-a1 interference, the study of the order of the phase transition at large μB, the onset of the deconfinement through J/ψ suppression and the transport properties of the medium via the measurement of open charm states.
Strangeness production will be studied by measuring the production of several strange hadrons through their hadronic decays.
In this talk the physics program of the NA60+ experiment will be described, together with its competitiveness and complementarity with respect to other experiments. The physics performances expected for hard and electromagnetic probes will be discussed. The capabilities for the measurement of ϕ, K0S, (anti-)Λ0, 三±, and Ω± production in central Pb-Pb collisions, reconstructed using the vertex telescope as a stand-alone detector will be presented.
The goal of LHCspin is to develop, in the next few years, innovative solutions and cutting-edge technologies to access spin physics in high-energy polarized fixed-target collisions, by exploring a unique kinematic regime given by the LHC beam and by exploiting new probes.
This ambitious task poses its basis on the recent installation of SMOG2, the unpolarized gas target in front of the LHCb spectrometer. Specifically, the unpolarized target, already itself a unique project, will allow to carefully study the dynamics of the beam-target system, and clarify the potentiality of
the entire system, as the basis for an innovative physics program at the LHC.
The forward geometry of the LHCb spectrometer $(2<\eta<5)$ is perfectly suited for the reconstruction of particles produced in fixed-target collisions. This configuration, with center-of-mass energies ranging from $\sqrt{s}_{NN}=115$ GeV in pp interactions to $\sqrt{s}_{NN}=72$ GeV in collisions with nuclear beams, allows to cover a wide backward rapidity region, including the poorly explored high x-Bjorken and high x-Feynman regimes. With the instrumentation of the proposed target system, LHCb will become the first experiment delivering simultaneously unpolarized beam-beam collisions at $\sqrt{s}=14$ TeV and both polarized and unpolarized beam-target collisions.
The status of the project is presented along with a selection of physics opportunities.
The Electron-Ion Collider (EIC) is a future particle accelerator to be built at the Brookhaven National Laboratory, and the primary purpose of experiments at the EIC is to resolve the question of partonic structure of nucleons and nuclei. To achieve the physics goals of the EIC, a hadron calorimeter of high energy resolution is required at forward rapidity. A Dual-readout Calorimeter (DRC) which has been developed for future collider experiments is considered as an upgrade option of the forward hadron calorimeter for the ECCE experiment at the EIC. The DRC consisting of two types of optical fiber, Cherenkov and Scintillation fibers, can achieve high energy resolution by measuring a fraction of electromagnetic shower in a hadronic shower. A performance study of DRC for the EIC such as geometry, material, and energy resolution is ongoing based on the existing simulation framework for high energy experiments, and the DRC simulation details will be transported to the EIC simulation framework. In this presentation, we will introduce the simulation study of the DRC for the EIC.
The sPHENIX experiment at RHIC is currently under construction and on schedule for first data in early 2023. Built around the excellent BaBar superconducting solenoid, the central detector consists of a silicon pixel vertexer adapted from the ALICE ITS design, a silicon strip detector with single event timing resolution, a compact TPC, novel EM calorimetry, and two layers of hadronic calorimetry. The hybrid streaming/triggered readout of the detector enables full exploitation of the luminosity provided by RHIC.
The talk will describe the readiness of the experiment for operations, present current projections of key jet and heavy flavor measurements, and discuss their potential scientific impact.
We discuss elliptic and triangular flow of charmonia in heavy ion collisions based on the coalescence model. Starting from the investigation on transverse momentum distributions of charmonium states, we calculate elliptic and triangular flow of charmonium states produced at quark-hadron phase boundary by quark recombination. We show that the wave function distribution of charmonium states plays a significant role, especially in the production of charmonium states, leading to the transverse momentum distribution of the ψ(2S) meson as large as that of the J/ψ meson. On the other hand, we find that wave function distributions as well as feed-down contributions are averaged out for elliptic and triangular flow, resulting in similar elliptic and triangular flow for all charmonium states. Based on our evaluation of elliptic and triangular flow of charmonium states we also discuss the quark number scaling of elliptic and triangular flow for charmonium states in heavy ion collisions.
One of the present challenge for the theoretical understanding of heavy-quark hadronization is represented by the description of the measurements of heavy baryon production in $pp$, $pA$ and $AA$ collisions from RHIC to top LHC energies.
The $\Lambda_c/D^0$ ratio observed in $AA$ collisions has a value of the order of the unity, and experimental measurements in $pp$ collisions at both $\sqrt{s}=5.02 \,\rm TeV$ and $\sqrt{s}=13 \,\rm TeV$ have shown ratios for charm baryons $\Lambda_c$, $\Xi_c^0$ and $\Omega_c^0$ respect to $D^0$ meson larger than that measured and expected in $e^+e^-$, $ep$ collisions.
With a relativistic Boltzmann transport approach we study the propagation of charm quarks in the quark-gluon plasma (QGP), with the non-perturbative interaction between heavy quarks and light quarks described by a quasi-particle approach, then we apply an hadronization mechanism based on the coalescence and fragmentation processes. We present this model and the results obtained in $AA$ collisions for $D^0$, $D_s$, $\Lambda_c$ spectra and the related baryon to meson ratios at RHIC and LHC. where we have found a large $\Lambda_c$ production resulting in a baryon over meson ratio of order O(1). We have furthermore extended this approach to study the production of hadrons containing multiple charm quark, i.e. $\Xi_{cc}$, $\Omega_{cc}$ and $\Omega_{ccc}$, we present here new predictions of these productions in different collision system (PbPb, KrKr, ArAr).
We present moreover results obtained for the charmed hadron production in $pp$ collisions at top LHC energies assuming the formation of an hot QCD matter at finite temperature for these systems.
We calculate the heavy baryon/meson ratio and the $p_T$ spectra of charmed hadrons with and without strangeness content: $D^{0}$, $D_{s}$, $\Lambda_{c}^{+}$, $\Sigma_{c}$ and the recently measured $\Xi_c$ baryon, finding an enhancement in comparison with the ratio observed for $e^+e^-$, $ep$ collisions; with this approach we also predict a significant production of $\Omega_c$ respect to $D^0$ such that $\Omega_c/D^0 \sim 0.15$.
[1] V. Minissale, S. Plumari and V. Greco, Physics Letters B 821 (2021) 136622.
[2] S. Plumari, V. Minissale, S.K. Das, G. Coci and V. Greco, Eur.Phys.J. C 78 (2018) no.4, 348
The propagation of heavy quarks (HQs), charm and bottom, in the quark-gluon plasma (QGP) is described by means of a full Boltzmann transport approach. The non-perturbative dynamics and the interaction between HQs and the bulk is taken into account by means of a Quasi-Particle Model. Including the description of the intense electromagnetic and vortical fields, we discuss their impact on the directed flow of neutral D mesons at RHIC and LHC energy, clarifying the powerful role of this observable in giving information on the transport properties of the hot QCD matter generated in ultra-relativistic collisions. Indeed, the $v_1$ magnitude is associated with the HQ diffusion coefficient while the $v_1$ splitting is connected to the electric conductivity of the QGP medium.
We also show our results for the D-meson $R_{AA}$ and $v_n$ at RHIC and LHC energies within a coalescence plus fragmentation hadronization scheme and including event-by-event initial state fluctuations. We highlight the role of the latter on the development of $v_3(p_T)$ and $v_4(p_T)$. We discuss event-shape selected D-meson spectra and $v_n$ as well as correlations between different D-meson flow coefficients at LHC energies in different centrality classes. The centrality selection is performed according to the magnitude of the second-order harmonic reduced flow vector $q_2$. The extracted temperature dependence of the spatial diffusion coefficient $D_s$ is consistent with lattice QCD results within the systematic uncertainties. Furthermore, we present predictions for $R_{AA}$, $v_2$ and $v_3$ of B mesons and electrons from semi-leptonic B-meson decays at top LHC energies. We find a remarkable suppression al low $p_T$, leading to a determination of $D_s$ that is in agreement with the lattice QCD calculations.
[1] L. Oliva, S. Plumari and V. Greco, JHEP 05, 034 (2021).
[2] S. Plumari, G. Coci, V. Minissale, S.K. Das, Y. Sun and V. Greco, Phys. Lett. B 805, 135460 (2020).
[3] F. Scardina, S.K. Das, V. Minissale, S. Plumari and V. Greco, Phys.Rev. C 96, 044905 (2017).
The phenomenon of strangeness enhancement, originally proposed as a signature of quark-gluon plasma formation, has received considerable new interest following recent observations in small collision systems. LHCb is uniquely well suited to study such effects in the heavy quark sector, down to very low transverse momentum. Here we will present new LHCb results on the production rates of $B_{s}^{0}$ relative to $B^{0}$ mesons and $D_{s}^{+}$ relative to $D^{+}$ mesons versus multiplicity in $pp$ and $p$Pb collisions. Potential implications for the hadronization mechanism of heavy quarks and our understanding of the factorization of fragmentation functions will be discussed.
Heavy flavour and quarkonium production at hadron colliders provides an important test of the theory of Quantum Chromodynamics (QCD). The PHENIX experiment has a comprehensive physics program that studies open heavy flavor and quarkonium production in p/d+A and A+A collisions at the Relativistic Heavy Ion Collider (RHIC). It is critical to measure both open heavy flavor and quarkonium in different collision systems as a function of energy, centrality, and rapidity in order to disentangle cold (initial state) and hot nuclear medium (final) effects. The heavy quarks (charm and beauty) are predominantly produced in the early stage of the collisions via hard partonic scattering processes. Therefore, they experience the full evolution of the nuclear medium.
This talk will report the latest heavy flavor and quarkonium analysis results measured by PHENIX in p+p, p+Al, p+Au, He+Au, and Au+Au collisions as a function of centrality, rapidity, and transverse momentum, and interpretation of the results with respect to the current theoretical understanding.
The formalism of Baier-Dokshitzer-Mueller-Peigné-Schiff and Zakharov (BDMPS-Z) determines modifications of parton splittings in the QCD plasma that arise from medium-induced gluon radiation. Here, we extend the BDMPS-Z formalism to medium-modifications of the gluon splitting into two massive quarks of mass m. We derive a compact path-integral formulation that resums effects from arbitrary many interactions with the medium. We identify two qualitatively different phenomena: a medium-induced momentum broadening that increases the invariant mass of quark-anti-quark pair and a medium-enhanced production of such pairs. We note that both effects are numerically sizeable if the average squared momentum transfer from the medium is comparable to $m^2$. In ultrarelativistic heavy-ion collisions, this condition is satisfied for cham quarks.
Neutron stars harbor extreme conditions unattainable in terrestrial laboratories,
making them ideal candidates to study the equation of state (EoS) of strongly interacting matter. Advancements in the measurements of neutron star masses, radii
and tidal deformabilities through electromagnetic and gravitational wave observations have made it feasible to add further constraints on the EoS. In this work, we present a novel method that exploits deep learning techniques to reconstruct the neu-tron star EoS from mass-radius (MR) observations. Our approach makes use of an unsupervised learning procedure in the Automatic Differentiation framework to optimize the EoS. We demonstrate that our proposed method successfully reconstructs the EoS using merely 12 mock MR data, which is nearly equivalent to the current number of observations. We deploy our deep learning methodology on existing MR observations, including the recent data from NICER, to infer the neutron star EoS. The reconstructed EoS band is consistent with conventional nuclear EoS models. We further demonstrate that our results are congruous with the bounds on tidal deformability obtained from the gravitational wave event, GW170817.
In the journey to explore the strong interaction among hadrons, ALICE has for the first time flared out its femtoscopic studies to nuclei. The large data sample of high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV allows the measurement of the proton-deuteron (p-d), the kaon-deuteron (K$^\pm$-d), and the Lambda-deuteron ($\Lambda$-d) momentum correlations. The femtoscopic study of these systems opens the door to investigate the formation mechanism of the light nuclei in hadron-hadron collisions.
In this contribution, the measured correlation functions for p-d, K$^\pm$-d, and $\Lambda$-d are presented and compared to theoretical predictions. In the case of p-d correlations, the data shows a shallow depletion at low relative momenta, while the full-fledged model calculations which include all relevant interactions predict a strong repulsive signal. Possible explanations include a late formation of the deuterons leading to the suppression of strong interactions between protons and deuterons. Likewise, the experimentally obtained K$^\pm$-d correlation function shows a Coulomb-like depletion which is well reproduced by the theoretical two-body Coulomb interaction. This result presents a complementary information to the p-d on the late formation of deuterons. In addition, the measured $\Lambda$-d correlation is in agreement with hypothesis of no strong interaction due to the late formation of deuterons, supporting the findings in p-d. In general, we demonstrate how correlation functions can be exploited to study the production mechanism of light nuclei at the LHC.
Strong electromagnetic field arising from the Lorentz-contraction and a large number of charges (Z) in the colliding nuclei at ultrarelativistic speeds can generate a large flux of quasi-real photons. Consequent photon-induced interactions could reasonably explain the observed enhancements of $J/\psi$ and $e^{+}e^{-}$ pair productions at very low transverse momenta ($p_{T}$) in peripheral high-energy heavy-ion collisions, via photonuclear ($\propto$ $Z^{2}$) and photon-photon ($\propto$ $Z^{4}$) processes. The STAR experiment has collected a large sample of $^{96}_{44}\mathrm{Ru}$+$^{96}_{44}\mathrm{Ru}$ and $^{96}_{40}\mathrm{Zr}$+$^{96}_{40}\mathrm{Zr}$ collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV in 2018. The isobaric collisions, with different number of charges and same number of nucleons in the colliding nuclei, provide a unique opportunity to test the electromagnetic field dependence of photon-induced production.
In this presentation, we will present the first measurement of the electromagnetic field dependence of $J/\psi$ and $e^{+}e^{-}$ pair productions at very low $p_{T}$, via comparisons between the new measurements in isobaric collisions as well as to the published results in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV. Besides, the angular modulation of dielectron pairs in isobaric collisions which is related to vacuum birefringence will also be presented. The physical implications of these results will be discussed.
Space: the final frontier for antinuclei physics. There, antinucleosynthesis models already tested on the bench of hadronic colliders and particle physics experiments are put at work to crack one of the biggest problems of modern physics: the existence and nature of dark matter.
In fact, the observation of an antinucleus in cosmic rays would most probably mean a breakthrough in searches for Dark Matter. However, to correctly interpret future results, precise knowledge of both the antinuclei production mechanism and their nuclear inelastic cross sections is needed.
The ALICE collaboration already investigated in detail the anti nucleosynthesis models in small and large collision systems at the LHC and has recently performed several measurements of antideuteron, $^3\overline{\text{H}}$ and $^3\overline{\text{He}}$ inelastic cross sections, providing the first experimental information of this kind.
In this talk, the final results on antideuteron and $^3\overline{\text{He}}$ inelastic cross-sections and the new results on $^3\overline{\text{H}}$ inelastic cross-sections are discussed as well how, thanks to them, it is possible to determine for the first time the transparency of the Galaxy to antinuclei stemming from dark matter and Standard Model collisions.
Motivated by strangeness enhancement implying the possible QGP (quark-gluon plasma) formation in small colliding systems, we extend the hydro-based framework incorporating non-equilibrated components which play an essential role in small colliding systems. It has been widely accepted that relativistic hydrodynamics well describes the dynamics of the QGP at low $p_{\mathrm{T}}$ regimes in large colliding systems. Hence hydro-based frameworks are used to tease out properties of the QGP in high-energy heavy-ion collisions. In contrast, particle productions in small colliding systems have been studied through QCD-motivated phenomenological models such as perturbative QCD (semi-)hard processes followed by string fragmentation. As keeping these pictures in each regime,
the ``marriage" of relativistic hydrodynamics and QCD-motivated phenomenological framework is indispensable to explore the dynamics over wide ranges of colliding systems.
We realize this as the dynamical core--corona initialization framework (DCCI) [1-3]. In DCCI, QGP fluids are generated from initial partons obtained from PYTHIA/PYTHIA Angantyr [4-5] which reflects the total energy-momentum of incoming nuclei. We phenomenologically describe the fluidization of the initial partons with the dynamical aspects of the core--corona picture. Partons with sufficient secondary scatterings tend to generate QGP fluids (core) as equilibrated matter.
While partons with insufficient secondary scatterings tend to survive as non-equilibrated matter (corona). This framework is, so to speak, the hydrodynamic afterburner for PYTHIA. By treating both locally equilibrated QGP fluids and non-equilibrated matter, DCCI, as a hydro-based Monte Carlo event generator, is capable of describing from low to high $p_{\mathrm{T}}$, from backward to forward rapidity, and from small to large colliding systems.
In this talk, we investigate the interplay between core and corona components in high-energy nuclear collisions using DCCI. Through the interplay, DCCI2 describes the smooth enhancement of strange hadrons reported by the ALICE Collaboration in p--p and Pb--Pb collisions. We reveal that the particle production from the core becomes dominant above $\langle dN_{\mathrm{ch}}/d\eta \rangle \sim 18$ regardless of the system size and the collision energy. Remarkably, the corona components turn out to dilute $\langle p_T \rangle$ and $v_2\{2\}$ obtained from the core components even in Pb--Pb collisions in which the entire system is often assumed to be locally equilibrated. These results suggest the importance of both equilibrated and non-equilibrated contributions in both small and large colliding systems towards an accurate understanding of the QGP properties.
[1] Y. Kanakubo, M. Okai, Y. Tachibana, and T. Hirano, PTEP 2018, 121D01 (2018).
[2] Y. Kanakubo, Y. Tachibana, and T. Hirano, Phys. Rev. C101, 024912 (2020).
[3] Y. Kanakubo, Y. Tachibana, and T. Hirano, Phys. Rev. C105 2, 024905 (2022).
[4] T. Sj\"{o}strand, S. Mrenna, and P. Z. Skands, Comput. Phys. Commun. 178, 852 (2008).
[5] C. Bierlich, G. Gustafson, L. L\"{o}nnblad, H. Shah, JHEP 10 134 (2018).
We analyze the behavior of cumulants of conserved charges in a subvolume of a thermal system with exact global conservation laws by extending [1] a recently developed [2] subensemble acceptance method (SAM) to multiple conserved charges. Explicit expressions for all diagonal and off-diagonal cumulants up to sixth order that relate them to the grand canonical susceptibilities are obtained. The derivation is presented for an arbitrary equation of state with an arbitrary number of different conserved charges. The global conservation effects cancel out in any ratio of two second order cumulants, in any ratio of two third order cumulants, as well as in a ratio of strongly intensive measures Σ and Δ involving any two conserved charges, making all these quantities particularly suitable for theory-to-experiment comparisons in heavy-ion collisions. We also show that the same cancellation occurs in correlators of a conserved charge, like the electric charge, with any non-conserved quantity such as net proton or net kaon number. The main results of the SAM are illustrated in the framework of the hadron resonance gas model. We also elucidate how net-proton and net-Λ fluctuations are affected by conservation of electric charge and strangeness in addition to baryon number.
[1] V.Vovchenko, R.V.Poberezhnyuk, V.Koch, JHEP 10 (2020) 089
[2] V.Vovchenko, O.Savchuk, R.V.Poberezhnyuk, M.I.Gorenstein, V.Koch, Phys.Lett.B 811 (2020) 135868
This talk presents new measurements of longitudinal flow decorrelations in 5.02 TeV and 13 TeV pp collisions and 5.44 TeV Xe+Xe collisions with the ATLAS detector. The measurements are performed using the two-particle correlation method with charged-particle tracks within |eta| < 2.5 and clusters within 4.0 < |eta| < 4.9. Due to the larger influence of non-flow effects in small collision systems, template-based subtraction procedures are developed and applied to the measurement. These effects are observed to play a role even in large systems such as 5.44 TeV Xe+Xe collisions. Flow decorrelations are characterized in terms of the ratio of the correlations with a large pseudorapidity gap to those with small pseudorapidity gap, r_n, where n is the flow harmonic moment. Results are reported for the slope of r_2 as a function of pseudorapidity gap as a function of charged-particle multiplicity for the pp and Xe+Xe collision systems. This gives some of the first detailed information on the correlation between longitudinal and transverse energy deposition in pp collisions.
Transport properties of the matter created in heavy-ion collisions, the quark-gluon plasma (QGP), contain essential information about quantum chromodynamics (QCD). In this talk, we present our latest study in inferring the transport properties of QGP by an improved Bayesian analysis using the CERN Large Hadron Collider Pb-Pb data. The uncertainties of the extracted properties are reduced by adding new observables sensitive to specific shear and bulk viscosity, reflecting mostly nonlinear hydrodynamic responses. The analysis also reveals that higher-order harmonic flows and their correlations have a higher sensitivity to the transport properties than other observables. This observation shows the necessity of accurate measurements of these observables including heavy quarks in the future.
Based on:
[1] J.E. Parkkila, A. Onnerstad, D.J. Kim, Phys.Rev.C 104 (2021) 5, 054904, arXiv: 2106.05019 [hep-ph]
[2] J.E. Parkkila, A. Onnerstad, S. F. Taghavi, C. Mordasini, A. Bilandzic, D.J. Kim, arXiv: 2111.08145 [hep-ph]
We present a novel approach to nonperturbatively estimate the heavy quark momentum diffusion coefficient, which is a key input for the theoretical description of heavy quarkonium production in heavy ion collisions, and is important for the understanding of the elliptic flow and nuclear suppression factor of heavy flavor hadrons. In the heavy quark limit, this coefficient is encoded in the spectral functions of color-electric and color-magnetic correlators that we calculate on the lattice to high precision by applying gradient flow. The color-magnetic correlator, which encodes the mass-suppressed contribution to the diffusion coefficient, is calculated for the first time on the lattice. In our study we consider quenched QCD at 1.5Tc, where we perform a detailed study of the lattice spacing and flow time dependence of color-electric and color-magnetic correlators, and, using theoretically well-established model fits for the spectral reconstruction, we estimate the heavy quark diffusion coefficient. Equipped with the experience obtained in quenched QCD, we estimate the heavy quark diffusion coefficient from 2+1 flavor QCD ensembles at small but finite lattice spacing.
We present equilibrium as well as out-of-equilibrium properties of the strongly interacting QGP medium under extreme conditions of high temperature $T$ and high baryon densities or baryon chemical potentials $\mu_B$ within a kinetic approach. We will explore first the thermodynamic and transport properties of the QGP close to equilibrium in the framework of effective models with $N_f=3$ active quark flavours such as the Polyakov extended Nambu-Jona Lasinio (PNJL) [1] and dynamical quasiparticle model with the CEP (DQPM-CP) [2]. Considering the transport coefficients and the EoS of the QGP phase, we compare our results with various results from the literature. Moreover, we find a good agreement between resulting transport coefficients at $\mu_B=0$ to the predictions from the lattice QCD and estimates from a Bayesian analysis by the JETSCAPE Collaboration.
Furthermore, out-of equilibrium properties of the QGP medium and in particular, the effect of a $\mu_B$ - dependence of thermodynamic and transport properties of the QGP are studied within the Parton-Hadron-String-Dynamics (PHSD) transport approach [3,4].
The PHSD covers the full evolution of the system during HICs, including the partonic phase as well as the phase transition between the hadronic and partonic phases, where the microscopic properties of quarks and gluons are described by the DQPM.
The DQPM, which is based on the lQCD data, interprets the EoS in terms of dynamical degrees of freedom and allows evaluating the cross sections of the corresponding elastic and inelastic reactions, which are essential for the transport evolution.
The microscopic properties of partonic quasiparticles and their differential cross sections depend not only on the temperature $T$ but also on the chemical potential $\mu_B$ explicitly in these studies.
We find that bulk observables and flow coefficients for strange hadrons as well as for antiprotons are more sensitive to the properties of the QGP, in particular to the $\mu_B$ - dependence of QGP interactions.
[1] O. Soloveva, D. Fuseau, J. Aichelin and E. Bratkovskaya,
Phys. Rev. C 103 (2021) no.5, 054901
[2] O. Soloveva, J. Aichelin and E. Bratkovskaya,
Phys. Rev. D 105 (2022) no.5, 054011
[3] W. Cassing and E. L. Bratkovskaya,
Nucl. Phys. A 831 (2009), 215-242
[4] P. Moreau, O. Soloveva, L. Oliva, T. Song, W. Cassing and E. Bratkovskaya,
Phys. Rev. C 100 (2019) no.1, 014911
A major focus of recent experiments in heavy-ion collisions is to reveal rich phase structure in high baryon density matter: the first-order chiral transition line with the QCD critical point, CSC phase transition and so on. Such experiments include the beam-energy scan program at RHIC, and HADES and NA61/SHINE collaborations as well as those to be performed in future experimental facilities such as FAIR, NICA and J-PARC-HI. In the present report, we calculate how the soft modes that develop around CSC phase transition and QCD critical point, affect the dilepton production rate based on the two-flavor NJL model. It is demonstrated that Aslamazov-Larkin, Maki-Thompson and DOS terms due to the soft modes, which are known to give rise to anomalous excess of electric conductivity in metals, modify the photon self-energy so greatly that the dilepton production rates is enhanced anomalously at the low energy region.
First experimental results on the third-order cumulants of net-proton fluctuations, as well as second-order cumulants of net-pion and net-kaon fluctuations, in Pb-Pb collisions recorded by the ALICE detector at the CERN LHC are presented. Resonance contributions are shown to pose the main challenge in the study of fluctuations in net-electric charge and net-strangeness. The results on second-order cumulants of net-proton fluctuations are also discussed in view of effects due to global/local baryon number conservation. The results exhibit the presence of long-range rapidity correlations between protons and antiprotons. These correlations originate from the early phase of the collision. The experimental results are compared with HIJING and EPOS model calculations, and the dependence of the fluctuation measurements on phase-space coverage is examined in the context of lattice QCD (lQCD) and Hadron Resonance Gas (HRG) model calculations. The data from ALICE agree with the lQCD and HRG expectations up to the third-order cumulants after baryon number conservation is taken into account. The lQCD calculations predict a significant deviation from the HRG model calculations for the 4$^{\rm th}$ and higher order cumulants. The analysis of the 4$^{\rm th}$ order cumulants is ongoing using a factor of 10 more data collected in 2018, while the measurement of the 6$^{\rm th}$ and higher order cumulants will be discussed in view of the High Luminosity LHC (HL-LHC) starting in 2022 and the future ALICE 3 detector scheduled to operate in the 2030s after the Long Shutdown 4 of the LHC.
Two-particle charge-dependent correlations (balance functions) are sensitive to the production and transport of conserved quantum numbers in the medium created in hadronic collisions. In this contribution, recent ALICE measurements of the balance functions of charge, strangeness, and baryon numbers are presented. Balance functions for all combinations of identified charged-hadron ($\pi$,K,p) pairs are calculated in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV as a function of collision centrality. The balancing in azimuthal angle and rapidity is expected to provide information about quark diffusion and delayed hadronization, respectively. For the latter, a possible two-stage quark-production scenario - early production of strange quarks and late production of light quarks - is discussed. In addition, balance function integrals of (un)identified hadron pairs as a function of collision centralities, which provide the information about different pairing probabilities, are calculated for the first time. To investigate further the strangeness enhancement with multiplicity in small systems, recent measurements of how the production of doubly-strange $\Xi$ baryons is balanced with mesons (strange kaons and non-strange pions) and baryons ($\Xi$, $\Lambda$, and p) in pp collisions at $\sqrt{s}$ = 13 TeV are shown. The balance is studied by triggering on $\Xi$ baryons and subtracting the same quantum number from the opposite quantum number per-trigger yields. In particular, the multiplicity dependence is studied in order to identify if the same strangeness-production mechanism is at work in low- and high-multiplicity pp collisions. The results are compared to predictions from Monte Carlo models with various tunes of PYTHIA 8 (Lund string-based approach) and EPOS LHC (based on core-corona approach).
In a non-central nucleus-nucleus collision, the colliding system carries large orbital angular momentum, part of which remains within the hot dense matter created by the collision. This angular momentum turns into complex fluid vorticity structures in the bulk fluid, and eventually manifests itself through nontrivial rotational polarization effects. Such quantum phenomena were known in condensed matter physics long ago and have renewed interests in the so-called spintronics research. In the subatomic regime, the STAR Collaboration reported in 2017 the experimental discovery of global hyperon spin polarization in heavy ion collisions. A crucial feature in establishing the interpretation is the predicted beam energy dependence, specifically a strong increase of fluid vorticity (and thus the polarization) when the collision beam energy is decreased from O(100) GeV to O(10) GeV range. Very recently, these measurements have been pushed toward GeV-beam-energy range in the RHIC Beam Energy Scan II as well as HADES experiment, showing an even stronger signal for hyperon global polarization. These results suggest the creation of a highly polarized strong interaction matter with substantial angular momentum transport in low energy collisions, thus offering a unique environment for exploring novel effects of rotational polarization. In this talk, we report a number of studies on this topic, including: (1) quantitative simulations to understand the hyperon production and its (somewhat surprisingly) strong polarization as well as the implications for angular momentum transport in the bulk matter along rapidity; (2) the progress and pressing issues in the development of a viscous hydrodynamic framework for relativistic fluids with finite angular momentum; (3) possible new phase structures under rotation and in particular the emergence of a new rho-superfluid phase due to interplay of isospin density and rotation, which are both available in low energy collisions. References: PRC104(2021)L041902; arXiv:2105.04060; CPC44(2020)111001; Scientific Reports 10(2020)2196; PLB798(2019)134929; Lect. Notes Phys 987(2021)1.
This talk presents the latest ATLAS measurements of heavy flavor and hard probes of the Quark-Gluon Plasma, with an aim towards understanding the energy loss mechanisms for probes of different mass and flavor through interactions with the QGP medium. These include recent measurements of open heavy flavor modification and flow in large and small collision systems, new measurements of b-jet and photon-jet production in Pb+Pb collisions, and measurements of HF-HF correlations in Pb+Pb collisions via di-muons.
Measurements of quarkonia production in peripheral and ultra-peripheral heavy-ion collisions are sensitive to photon-photon and photon-nucleus interactions, the partonic structure of nuclei, and to the mechanisms of vector-meson production. LHCb has studied both coherent and incoherent production of $J/\psi$ mesons in peripheral and ultra-peripheral collisions using PbPb data at forward rapidity with the highest precision currently accessible. Here we will present these measurements, along with comparisons with the latest theoretical models and with results from other experiments. Future UPC measurements with the upgraded LHCb detector in Run 3 will also be discussed.
The unique forward coverage of the LHCb spectrometer allows the valence quark distributions of protons and nuclei to be probed with unprecedented precision. In this high-$x$ region, both the flavor content and structure of the nucleon's parton distribution functions remain relatively poorly known. New LHCb measurements of $Z$+charm jet production could be indicative of a valence-like intrinsic-charm component in the proton wavefunction, and measurements of $Z$ production in $p$Pb collisions provide new constraints on the partonic structure of nucleons bound inside nuclei. Here we will discuss these new LHCb measurements and comparisons with state-of-the-art parton distribution function calculations.
Hydrodynamic models are a central component of nuclear collision phenomenology. In this talk, I show that relativistic causality is violated in the early stages of state-of-the-art heavy-ion hydrodynamic simulations of nuclear collisions. Up to 75% of the initial fluid cells violate nonlinear causality constraints, while superluminal propagation is observed by up to 15% the speed of light. Only after 2-3 fm$/c$ of evolution, do ∼50% of the fluid cells become definitely causal. Inclusion of pre-equilibrium evolution significantly reduces the number of acausal cells, but it does not eliminate them. These findings show that relativistic causality imposes constraints on the available model parameter space of heavy-ion collision simulations.
We present that the large single transverse spin asymmetry for the pion production in the very forward direction is diffractively produced. The differential cross section of the $p+p^\uparrow \to \pi^0+X$ can be expressed in terms of hybridized Regge amplitude and inclusive proton-baryon processes $A_{pB \to X}$. The interference of $p$ and $\Delta(1700)$ turns out to be dominant to $A_N$. In addition, the inclusive part of the differential cross section can be approximated as a triple-Regge diagram with pion exchange. Our numerical results show a good agreement with the $p_T$ and $x_F$ distribution from the RHICf experiment. The present study indicates that in the low $p_T$ region $A_N$ is of diffractive nature.
Heavy-ion collisions in the few GeV energy regimes probe similar temperatures and densities as created in neutron star mergers and provide a tool to probe cosmic matter in earthly laboratories [1]
In March 2019, the HADES collaboration recorded $13.7 \cdot 10^{9}$ Ag(1.58$A$~GeV)+Ag events as part of the FAIR Phase-0 program. Within this talk, we present preliminary results for yields and kinematic distributions of $K^{+}$, $K^{-}$ and $\phi(1020)$.
The presented strange hadrons are produced below the free nucleon-nucleon production threshold and thusly are a good probe for in-medium effects due to their steep excitation function. In this presentation, the relative yields of strange particles with different excitation energies are compared and their consistency with theoretical models and recent results of other experiments is reviewed. Especially comparing the $\phi(1020)$ with the $\Xi^-$ provides further insight into the accuracy of particle production yield calculations in statistical models. Furthermore, the system size dependence of strangeness production is tested by comparing central and peripheral collisions.
[1] Adamczewski-Musch, J., Arnold, O., Behnke, C. et al. Probing dense baryon-rich matter with virtual photons. Nat. Phys. 15, 1040–1045 (2019), doi:10.1038/s41567-019-0583-8
With a unique geometry covering the forward rapidity region, the LHCb detector provides unprecedented kinematic coverage at low Bjorken-$x$ down to $x \sim 10^{-5}$ or lower. The excellent momentum resolution, vertex reconstruction and particle identification allow precision measurements down to very low hadron transverse momentum. In this contribution we present the latest studies of the relatively unknown low-$x$ region using the LHCb detector, including recent measurements of charged and neutral hadron production, as well as direct photon and hadron correlations in proton-proton and proton-lead collisions. Comparisons to various theoretical model calculations are also discussed.
Matter-antimatter asymmetry is a precondition necessary to explain the existence of our world made predominately of matter over antimatter. Antimatter is rare in the current universe making it difficult to study, but the Relativistic Heavy-Ion Collider (RHIC) provides us a unique opportunity to study antimatter with high-energy nuclear-nuclear collisions.
In this talk, we will report the first observation of $\rm ^4_{\bar{\Lambda}}\bar{H}$ with the STAR experiment at RHIC. $\rm ^4_{\bar{\Lambda}}\bar{H}$ is the heaviest anti-hypernucleus ever observed in experiments. Its observation will bring new opportunities for the study of matter-antimatter asymmetry. We will also report the various production yield ratios among (anti-)hypernuclei and (anti-)nuclei, as well as the lifetime measurements of $\rm ^3_{\Lambda}H$, $\rm ^3_{\bar{\Lambda}}\bar{H}$, $\rm ^4_{\Lambda}H$, and $\rm ^4_{\bar{\Lambda}}\bar{H}$.
We calculate the yields of molecular configuration hadrons produced by heavy ion collision using coalescence model. First, we calculated the transverse momentum distribution of deuteron using the coalescence model from proton transverse momentum distribution in Pb-Pb collisions at 2.76TeV measured by ALICE collaboration. From this, we estimate the parameters required for coalescence model at kinetic freeze-out. We then calculate the transverse momentum distribution of helium-3 using this parameter and compared with the experimental results by ALICE collaboration to confirm that parameterizaion was successful. After this, we assume that X(3872) is molecular structures and estimate the transverse momentum distributions of X(3872) using coalescence model. Additionally, we predict the production of $X(3872)$ and $f_0(980)$ assuming they are loosely bounded molecular configurations using the large size limit of hadron in coalescence model. Also, we compare the yields of these hadrons calculated using coalescence model with statistical hadronization model.
For the first time, a single equation of state is used for dynamical simulations of binary neutron-star mergers and heavy-ion collisions [1]. That is done by employing the Chiral Mean Field (CMF) equation of state (EOS) [2] in self-consistent relativistic-hydrodynamic calculations for both systems. A direct comparison of the evolution of physical quantities like temperature, entropy, and baryon density in both systems allows to conclude that conditions created during these events are identical. A particular outcome of such an analysis is the universality of isentropes S/A=[1.8, 2.2] to describe bulk evolution of both binary neutron star mergers with $M_{\rm tot} = 2.6 − 2.8 M_\odot$ and heavy-ion collisions at the beam energies $E_{\rm lab} = [450, 600]$ A MeV. This provides concrete evidence that the physical conditions reached in binary neutron-star mergers can be studied in the present and future laboratory experiments.
Since the low energy collisions allow to study conditions of stellar neutron star mergers, it is important to understand up to which extent the QCD equation of state can be probed in the laboratory. The use of the hydrodynamic picture to describe experimental data at these collision energies is cumbersome since it strongly relies on the particlization routine. To tackle that, a procedure to incorporate any equation of state in the UrQMD microscopic transport model is introduced [3]. We employ the same CMF EOS in the transport simulations of heavy-ion collisions and compare them to the results of relativistic hydrodynamics. It is found that initial compression is similar if the same EOS is used in either dynamical model, but it also strongly depends on the actual EOS. These results indicate that the EOS can be unambiguously studied with observables that are sensitive to the initial compression phase in heavy-ion collisions.
[1] E. R. Most, A. Motornenko, J. Steinheimer, V. Dexheimer, M. Hanauske, L. Rezzolla and H. Stoecker, ``Probing neutron-star matter in the lab: connecting binary mergers to heavy-ion collisions,'' [arXiv:2201.13150 [nucl-th]]
[2] A. Motornenko, J. Steinheimer, V. Vovchenko, S. Schramm and H. Stoecker, ``Equation of state for hot QCD and compact stars from a mean field approach,'' [arXiv:1905.00866 [hep-ph]]
[3] M. O. Kuttan, A. Motornenko, J. Steinheimer, H. Stoecker, Y. Nara and M. Bleicher, ``A Chiral Mean-Field Equation-of-State in UrQMD: Effects on the Heavy Ion Compression Stage,'' [arXiv:2201.01622 [nucl-th]]
Lecture will be served in KOREAN language only, without official interpretation/traslation service to other language(english etc.).
Title: Us, in Universe, From Big-bang to Present
Time: 19h30-21h30 (2hrs.), 15 June 2022
Venue: 2F Grand ballroom, Paradise Hotel Busan
(296, Haeundaehaebyun-ro, Haeundae-gu, Busan, Republic of Korea)
Lecturer:
- Prof. Dr. In-Kwon Yoo (Dept. of Physics, Pusan National University)
- Prof. Dr. Chang-Hwan Lee (Dept. of Physics, Pusan National University)
Chair: Jinhee Yoon (Dept. of Physics, Pusan National University)
Organized by SQM2022 Local Organizing Committee and Secretariat
Because of the hygiene measure and the limitation of seats, please register at the following webpage
https://indico.kps.or.kr/e/sqm2022-public
주제: 빅뱅 우주 속의 우리
일시: 2022년 6월 15일 7시 30분 - 9시 30분(2시간)
장소: 부산 해운대 파라다이스호텔 본관 2층 그랜드볼룸
(부산광역시 해운대구 해운대해변로 296)
연사: 유인권교수 (부산대학교 물리학과), 이창환교수 (부산대학교 물리학과)
진행: 윤진희교수 (인하대학교 물리학과)
언어: 한국어 (타 언어 통역 및 번역 미제공)
주최/주관: 국제기묘도쿼크물질학술대회 조직위원회, 사무국
좌석 수 제한과 코로나19 방역 조치로, 아래 웹페이지에서 사전 참석 등록을 부탁드립니다.
The Rare Isotope Science Project (RISP) of the Institute for Basic Science (IBS), launched in late 2011 to build the Rare Isotope Accelerator complex for ON-line experiment (RAON) for rare isotope science, is preparing for commissioning on low energy superconducting linear accelerators (SCL3) with Argon-40. SCL3 commissioning involves integrated testing of cryogenic plants for superconducting linac and related instrumentations for beam commissioning. Also, ISOL (Isotope Separator On-Line), an important facility for producing rare isotopes (RI) and providing RI ion beams for ultra-low energy facilities of MR-TOF and Collinear laser spectroscopic(CLS) systems, is progressing with machine studies using stable ion beams and expects to commission with 70 MeV proton beam from Cyclotron aiming to produce of Na isotopes using SiC target. Therefore, including the low energy experimental system KoBRA (KOrea Broad acceptance Recoil spectrometer & Apparatus) and other experiment systems, the current effort to finish phase-1 of the project in 2022 is reported with future perspectives of RAON.