- Compact style
- Indico style
- Indico style - inline minutes
- Indico style - numbered
- Indico style - numbered + minutes
- Indico Weeks View
Welcome to the 50th edition of the ISMD conference series, bringing together physicists from across particle, nuclear, and astro-physics for talks and discussions on all aspects and consequences of the strong force and complex final states.
Due to the ongoing health risks and travel restrictions of the Covid-19 pandemic, ISMD2021 operated as a virtual conference from 12-16 July 2021. The conference fee was waived.
All talks were recorded, and you can access them via the contribution entries in the timetable: the video files are attached, equivalent to slide PDFs.
All scientific sessions at ISMD are in plenary session to encourage cross-talk between areas, organised into the following scientific tracks:
as well as discussion sessions, a poster session with a prize sponsored by the Universe journal, and associated short plenary talks for poster presenters.
Follow @ismdconf on Twitter
ISMD logo design by Ian Lucietti.
Measurements of two-particle correlations in $pp$ collisions show the presence of long-range correlations along $\Delta\eta$ that are strikingly similar to those seen in heavy-ion collisions. In heavy-ion collisions, the long-range correlations are known to arise from the collective dynamics of the produced quark-gluon plasma (QGP). The similarity between the $pp$ and heavy-ion measurements raises the possibility that a tiny droplet of the QGP is produced even in $pp$ collisions. However, models that attribute the origin of these correlations to semi-hard processes can also qualitatively reproduce the features observed in earlier measurements. Recently, multiple measurements have been performed that aim to further investigate the origin of these features in $pp$ collisions. This talk presents an overview of these recent measurements. These include measurements that study the dependence of the correlations on the presence of a hard process in the event, such as a high-$p_{\mathrm{T}}$ jet or a $Z$-boson. Studies of the long-range correlations where one of the particles in the pair is a muon produced from the decay of a heavy-flavor quark are discussed. Finally, correlation measurements with an active rejection of particles associated with semi-hard processes, such as low-pT jets, are also discussed. These measurements can give further insight into the origin of the long-range correlations observed in $pp$ collisions.
Efforts to understand QGP signatures using perturbative QCD models have been an active field since the first observation of the near-side long-range two-particle correlations in p-p collisions at the LHC in 2010. On the other hand, tools like Monte Carlo event generators, particularly PYTHIA, have been quite successful at describing LEP physics and also p-p phenomenology. This surprise element in p-p collisions sparked the need to probe nuclear collisions more closely via string dynamics. Currently, nuclear collisions can be generated within PYTHIA by the Angantyr framework (arXiv:1806.10820) which uses the p-p MPI framework in PYTHIA along with an advanced instance of the Glauber model. Hence, non-perturbative processes such as string interactions, called string shoving(arXiv:1710.09725 and arXiv:2010.07595) and rope hadronization(arXiv:1412.6259), have been studied which are main workhorses to generate QGP signals in collision systems within PYTHIA8. Such analyses come coupled with the challenges of formulating an approach that can treat both high and low multiplicity events with the same physical picture and also all partons in an event equally, regardless of their pT.
In order to include string interactions in a whole event, a new approach with a Lorentz frame, called the parallel frame, has been constructed that accommodates all strings formed in an event, regardless of the pT of the partons forming the strings. Once a PYTHIA event is generated, every possible pair of strings are then boosted to this parallel frame, where we hadronize the strings via rope formation and also include shoving between the strings. They are then boosted back to the laboratory frame where the successive processes follow. This is a novel tool that has the capacity to reproduce the QGP signals such as strangeness enhancement and flow in both small and large systems. In this talk, we present our new scheme and present results that explore to see if this formulation can achieve the particle production yields and their v_2 as seen in data.
We explore Glauber Monte Carlo predictions for the planned ultra-relativistic 16O+16O and p+16O collisions, as well as for collisions of 16O on heavy targets [1]. In particular, we present specific collective flow measures which are approximately independent on the hydrodynamic response of the system, such as the ratios of eccentricities obtained from cumulants with different numbers of particles, or correlations of ellipticity and triangularity described by the normalized symmetric cumulants. We use the state-of-the-art correlated nuclear distributions for 16O and compare the results to the uncorrelated case, finding moderate effects for the most central collisions. We also consider the wounded quark model, which turns out to yield similar results to the wounded nucleon
model for the considered measures. The purpose of our study is to prepare some ground for the upcoming experimental proposals, as well as to provide input for possible more detailed dynamical studies with hydrodynamics or transport codes.
[1] M. Rybczynski, W. Broniowski, Phys. Rev. C 100, 064912
Hydrodynamic expansion and jet quenching are responsible for the production of low and high transverse-momentum ($p_T$) particle in heavy-ion collisions, respectively. However, it is still a challenge to simultaneously describe hadron nuclear modification factor $R_{AA}$ and elliptic flow $v_2$, especially in the intermediate $p_T$ region of 2<$p_T$<10 GeV/c. In this talk, besides hydrodynamics and jet quenching, we also study the effects of the quark coalescence and the hadron cascade on hadron spectra and flow. We find the key to solving the $R_{AA}\otimes v_2$ 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 $R_{AA}$ 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 high-energy heavy-ion collisions. Our prediction is an example of high-precision tests of the quark coalescence model in nuclear collisions.
[1] Wenbin Zhao, Weiyao Ke, Wei Chen, Tan Luo and Xin-Nian Wang,arXiv:2103.14657 [hep-ph].
[2] Wenbin Zhao, Che-Ming Ko, YuXin Liu, Guangyou Qin and Huichao Song, Phys. Rev. Lett. 125, 072301 (2020).
Precise and detailed QCD calculations are crucial for high-energy collider phenomenology. This very often entails a matching of (detailed) Monte-Carlo event generators and (precise) fixed-order calculations.
This contribution discusses a next step in high-precision event generators: N3LO+PS matching within the T(hird) O(rder) M(atched) T(ransition) E(vents) scheme. Further, a non-parametric issue of some lower-order matching schemes (that had to be amended at N3LO) is discussed.
Several important processes and analyses at the LHC are sensitive to higher-order perturbative corrections beyond what can currently be calculated at fixed order. One important class of large logarithmic corrections are so-called high-energy logarithms which appear when the centre-of-mass energy of a QCD collision is much larger than the transverse momenta of the observed jets.
The effect of these logarithms is enhanced when there is a large rapidity separation between jets. It is therefore particularly important to study the effect of these higher-order corrections in, for example, the analysis of Higgs boson production in association with jets, as vector-boson fusion cuts provide exactly this enhanced impact to the gluon-fusion channel.
In this talk I will describe the High Energy Jets framework, which includes the dominant high-energy logarithms to provide all-order predictions for several relevant LHC processes including Higgs, W, or Z boson production in association with at least two jets. I will summarise the results from arXiv:1812.08072 and arXiv:2012.10310 and some ongoing work.
The presence of a non-baryonic Dark Matter (DM) component in the Universe is inferred from the observation of its gravitational interaction. If Dark Matter interacts weakly with the Standard Model (SM) it could be produced at the LHC. The ATLAS and CMS experiments have developed a broad search program for DM candidates, including resonance searches for the mediator which would couple DM to the SM and searches with large missing transverse momentum which is produced in association with other particles (e.g. light and heavy quarks, Z and H bosons) called mono-X searches. Additionally, searches have been conducted in models where the Higgs boson provides a portal to the Dark Sector leading to either invisible Higgs boson decays or decays with long lived particle requiring special reconstruction techniques. The results of recent searches on 13 TeV pp data, their interplay and interpretation will be presented.
Light nuclei, such as deuteron and triton, are loosely bound objects. Their yields are expected to be sensitive to baryon density fluctuations and can be used to probe the QCD critical point and the signatures of a first-order phase transition in heavy-ion collisions. In 2018, RHIC started the second phase of the beam energy scan program (BES-II). The STAR Fixed Target (FXT) program was proposed to achieve lower center-of-mass energies and higher baryon density regions. Up to now, the STAR experiment has recorded high statistics data at $\sqrt{s_{\mathrm{NN}}}$ = 3 - 7.7 GeV in Au+Au collisions.
In this talk, we will present light nuclei production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV (FXT) recorded by the STAR experiment in 2018. We will show the transverse momentum spectra of proton ($p$), deuteron ($d$), triton ($t$), $^{3}\mathrm{He}$, and $^{4}\mathrm{He}$ at various rapidity ranges. The rapidity and centrality dependence of coalescence parameters $B_2(d)$, $B_3(t)$, and $B_3({ }^{3}\mathrm{He})$, and particle ratios ($d/p$, $t/p$, $t/d$, $^{3}\mathrm{He}/p$ and $^{4}\mathrm{He}/p$) will be shown. In addition, the kinetic freeze-out temperature $T_{\mathrm{kin}}$ and average radial flow velocity $\langle\beta\rangle$ will also be discussed.
The polarization properties of $\Lambda$ and $\overline{\Lambda}$ have received increasing attention over the last years due to the possibility to
link this observable to the properties of the medium produced in relativistic heavy-ion collisions. For semi-central collisions, the matter density profile in the transverse plane develops an angular momentum, which can be quantified in terms of the thermal vorticity. Under appropriate conditions, the latter can be transferred to spin degrees of freedom and be observed as a global polarization. The Beam Energy Scan (BES) at RHIC, performed by the STAR Collaboration has shown a trend for the $\Lambda$ and $\overline{\Lambda}$ global polarization to increase as the energy of the collision decreases and that this increase is faster for $\overline{\Lambda}$s than for $\Lambda$s. In addition, the HADES Collaboration has recently provided preliminary results on the $\Lambda$ global polarization in Au+Au collisions at $\sqrt{s_{NN}}= 2.42$ GeV finding a non-vanishing result. In order to describe this behavior, we have developed the {\it core-corona model} where the source of $\Lambda$s and $\overline{\Lambda}$s is taken as a high-density core and a less dense corona. We show that when the larger abundance of $\Lambda$s compared to $\overline{\Lambda}$s coming from the corona is combined with a smaller number of $\Lambda$s coming from the core compared to those from the corona, which happens for collisions with intermediate to large impact parameters, an amplification effect for the $\overline{\Lambda}$ polarization can occur, in spite of the intrinsic $\Lambda$ polarization being larger than the intrinsic $\overline{\Lambda}$ polarization. This amplification is more prominent for lower collision energies. In this talk, I show that the model predicts that both the $\Lambda$ and $\overline{\Lambda}$ polarization peak with different intensities and at different energies within the HADES/NICA energy range.
This talk will be based on our recent work (arXiv:2105.03989 [hep-ph]) where we present a procedure to separate boosted Higgs bosons decaying into hadrons, from the background due to strong interactions. We employ the Lund jet plane to obtain a theoretically well-motivated representation of the jets of interest and we use the resulting images as the input to a convolutional neural network. In particular, we consider two different decay modes of the Higgs boson, namely into a pair of bottom quarks or into light jets, against the respective backgrounds. The performance of the tagger is compared to what is achieved using a traditional single-variable analysis which exploits a QCD inspired color-singlet tagger, namely the jet color ring observable. Furthermore, we study the dependence of the tagger’s performance on the requirement that the invariant mass of the selected jets should be close to the Higgs mass.
LHCb is a spectrometer that covers the forward region of proton-proton collisions, corresponding to the pseudo-rapidity range 2<eta<5. In this unique phase space, LHCb can perform tests of perturbative and non-perturbative QCD models, by studying the production of heavy flavor quarks, like charm and top quarks. In this context the production of a Z boson in association with a c-jet can be studied to measure the intrinsic charm content of the proton. Moreover LHCb can test phenomenological models of soft QCD processes, by measuring the production of forward hadrons in pp collisions.
The main goal of the STAR experiment is to study the properties of QCD matter at extreme conditions, high temperature and/or high density, by colliding heavy ions at ultra-relativistic speed. The yields and particle ratios of strange hadrons provide important information about the particle production mechanisms in these collisions. The RHIC Beam Energy Scan program covers a wide range of energies to explore the transition from a hadronic dominated phase to a partonic dominated one. Of particular interest is the high baryon density region which is accessible through the STAR fixed-target program, which has extended the energy reach from $\sqrt{s_{\rm NN}}=7.7$ GeV down to 3.0 GeV.
This presentation will report the first measurements of $\phi$ meson and $\Xi^{-}$ hyperon production in Au+Au collisions at $\sqrt{s_{\rm NN}}=3$ GeV. After correcting for the detector acceptance and tracking efficiencies, invariant yields and rapidity density distributions of $\phi$ and $\Xi^{-}$ will be presented. The particle ratios $\phi/K^{-} $ and $\phi/\Xi^{-}$ will be shown. Those results will be compared to the thermal and transport model calculations to study the strangeness production, and particularly to test and constrain canonical ensemble calculations. Comparisons to measurements from other experiments at similar energies will also be discussed.
The world’s largest sample of J/ψ 1.3 billion events accumulated at the BESIII dector offers a unique opportunity to study light meson decays. In recent years the BESIII experiment has made significant progresses in eta/eta' decays, including observation of eta'->pi+pi- mu+mu-, search for the rare decays of eta’4pi0 and eta’gam gam eta as well as the search for CP violation in eta’pi+pi- e+e-. In addition, the prospects for the light meson decays with the available 10 billion J/ψ will also be discussed.
There have been recent updates to the three global PDF fits (CT, MSHT and NNPDF), all using significant amounts of data from the LHC, in addition to the non-LHC data sets that formed the core of previous iterations. Given the impact of the LHC data on the global PDF fits, and the impact that the new PDFs will have on physics comparisons at the LHC, it is crucial to perform a benchmarking among the PDFs and the predictions using these PDFs, similar in spirit to what was carried out for PDF4LHC15, widely used for LHC physics. The end result of this exercise will be a PDF4LHC21 set of PDFs, formed from the combination of the three global PDF sets. This talk will detail the benchmarking that has been performed, the similarities and differences observed, the future direction of this work and the potential impact of the PDF4LHC21 PDFs on precision physics at the LHC.
Semi-visible jets arise in strongly interacting dark sectors, where parton evolution includes dark sector emissions, resulting in jets overlapping with missing transverse momentum. The implementation of semi-visible jets is done using the Pythia Hidden valley module to duplicate the dark sector showering. In this work, several jet substructure observables have been examined to compare semi-visible jets and light quark/gluon jets. These comparisons were performed using different dark hadron fraction in the semi-visible jets (signal). The extreme scenarios where signal consists either of entirely dark hadrons or visible hadrons offers a chance to understand the effect of the specific dark shower model employed in these comparisons. Looking at the different dark hadron fractions additionally, allows to check whether the substructure is created by the interspersing of visible hadrons with dark hadrons, or from certain model dependencies.
Measurements of jet profiles in high-energy collisions are sensitive probes of QCD parton splitting and showering. Precise understanding of the jet structures are essential for setting the baseline not only for nuclear modification of jets in heavy-ion collisions, but also for possible semi-soft cold QCD effects such as multi-parton interactions (MPI) that may modify jets in high-multiplicity proton-proton collisions. We analyzed the jet radial profiles in simulations, and defined a multiplicity-dependent characteristic jet size that is universal in a broad range of model classes regardless of parton distributions and the presence or absence of MPI and color-reconnection [1].
In this contribution we demonstrate that the radial jet profiles in proton-proton collisions exhibit scaling properties with charged-hadron event multiplicity in the full experimentally accessible transverse-momentum range. Based on this we propose that the scaling behavior stems from fundamental statistical properties of jet fragmentation [2]. We also study the multiplicity distributions of events with hard jets and show that the charged-hadron multiplicity distributions scale with jet momentum. This suggests that the Koba--Nielsen--Olesen (KNO) scaling holds within a jet. The in-jet scaling is fulfilled without multiple-parton interactions (MPI), but breaks down in case MPI is present without color reconnection. Our findings imply that KNO scaling is violated by parton shower or MPI in higher-energy collisions [3]. Besides these results, newest findings on the flavor-dependence of scaling properties will also be presented.
[1] Z.V., R.V., G.G.B., Adv. High Energy Phys. 2019 (2019), 6731362, https://doi.org/10.1155/2019/6731362
[2] A.G., R.V., G. Papp, G.G.B., in Gribov-90 Memorial Volume: Algebraic Methods in QFT (2021), https://arxiv.org/abs/2008.08500.
[3] R.V., A.G., G.G.B., Phys. Rev. D 103, L051503 (2021), https://doi.org/10.1103/PhysRevD.103.L051503
The general concept of the $z$-scaling based on fundamental principles of self-similarity, locality, and fractality of strange and non-strange particle production in $p+p$ and $Au+Au$ systems at high energies is discussed. We present new results of analysis of $K^0_S-$ meson spectra in $Au+Au$ collisions obtained by the STAR Collaboration at RHIC using the $z$-scaling approach. The analyzed spectra were measured over a wide range of collision energy $\sqrt {s_{NN}}=7.7-200$ GeV and transverse momentum of produced particles for different centralities in the rapidity range $|y|<0.5$. The scaling behavior of the spectra in $z$-presentation as a function of the collision energy and centrality is demonstrated. The energy loss in dependence on the energy and centrality of the collisions and transverse momentum of the produced particle is estimated. New indication on self-similarity of fractal structure of nuclei and fragmentation processes with $K^0_S-$mesons produced in $Au+Au$ collisions at RHIC is obtained.
The notion of "scaling" (or scaling universality) has special importance in critical phenomena. The universality hypothesis reduces the great variety of physical situations to a small number of universality classes, which depend only on few parameters (critical exponents). The self-similarity and fractality of strange hadron production in $Au+Au$ collisions are expressed in terms of the $z$-scaling parameters which are fractal dimensions of the interacting structures and specific heat of the produced medium. Close to a critical transition point, the collective cooperative phenomena become independent of the microscopic details of the considered system and the scaling behavior should be sensitive to a change of these parameters.
The obtained results can be useful in search of signatures of a phase transition and critical point with strange probes and can serve as a benchmark for complex analysis of self-similar features of strange production in heavy ion collisions.
Our study is aimed at the high multiplicity region where the series of collective phenomena are predicted. This region of multiplicity is unique. We have succeeded to descend on topological cross sections three orders down and receive the evidence the formation of a pion (Bose-Einstein) condensate. Almost half of the kinetic energy of an incident proton turns into secondary pions. For explanation of the mechanism of multiple production the phenomenological model or the gluon dominance model has been developed. We also observe in the angular distribution of charged pions two noticeable peaks, which we interpret as Cherenkov radiation of gluons by quarks. We are currently manufacturing an electromagnetic calorimeter for solving the puzzle of excess yield of soft photons.
Forward-backward (FB) correlations of produced particles between symmetrically located pseudorapidity ($\eta$) intervals play an important role in understanding the dynamics of multiparticle interactions and their hadronization in different collision systems like hadronic or nuclear. Various experiments including CERN Super Proton Synchrotron (SPS) & the Large Hadron Collider (LHC), the Tevatron, the Relativistic Heavy Ion Collider (RHIC) observed sizeable FB correlation strength in heavy-ion collisions as well as in small collision systems.
In this contribution, we have studied charged-particle multiplicity and summed values of transverse momentum ($\it{p}_{\rm T}$) correlations in forward and backward hemispheres in $pp$ collisions at $\sqrt{s}$ = 13 TeV using the Monte-Carlo event generator, EPOS3 [1,2] featuring with and without hydrodynamical evolution of particles. The FB correlation strength is measured in different $\eta$ window widths ($\delta\eta$) and in different separation between the FB windows ($\eta_{gap}$). We have investigated the dependence of FB correlation strength on $\delta\eta$, $\eta_{gap}$, and different multiplicity classes. Due to unavailability of experimental data for the FB correlations at $\sqrt{s}$ = 13 TeV, we compared our results with the predictions from the Quark-Gluon String Model (QGSM) [3], which suggests that the general trends of FB correlation strength for both EPOS3 hydro and without hydro simulated $pp$ events at $\sqrt{s}$ = 13 TeV are similar to that of QGSM [3]. Our previous analysis on EPOS3 generated $pp$ collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV [4] also reveals similar behavior. Thus, the manifested similar behavior in FB correlation strength for hydro and without hydro events suggests that the analysis may not be much affected by the hydrodynamical evolution of bulk particles rather it may be due to multiparticle interactions and fluctuations.
Moreover, it is interesting to note that FB correlation strength tends to saturate at very high energy which is evident from the dependence of $\delta\eta$ weighted average of FB correlation strength with center-of-mass energies ($\sqrt{s}$ = 0.9, 2.76, 7 and 13 TeV). Thus, our study on FB correlations adds valuable information to understand the dynamics of particle production at LHC energy as well as encourages more experimental measurements in this direction.
References:
[1] K. Werner, B. Guiot, Iu. Karpenko, and T. Pierog, Phys. Rev. C 89, 064903 (2014).
[2] H. J. Drescher, M. Hladik, S. Ostapchenko, T. Pierog, and K. Werner, Phys. Rep. 350, 93 (2001).
[3] L.V. Bravina, J. Bleibel, E. E. Zabrodin, Phys. Lett. B 787, 146-152 (2018).
[4] M. Mondal et al., Phys. Rev. D 102, 014033 (2020).
A transformation of collision data into new data structures that are suitable for machine learning techniques is an importation direction for future research. This study shows the usability of rapidity-mass matrices (RMM) for general event classification and for anomaly detection in collision data. The proposed standardization of the input feature space can simplify searches for signatures of new physics at the LHC when using machine learning techniques. In particular, using Monte Carlo simulations, we illustrate how to improve signal-over-background ratios in searches for new physics, how to filter out Standard Model events for model-agnostic searches. Some ideas related to anomaly detection in collision data are discussed. This work is based on https://arxiv.org/abs/1810.06669 (Universe (2021) 7(1), 19)
Two-particle transverse momentum correlation functions are a powerful technique for understanding the dynamics of relativistic heavy-ion collisions. Among these, the transverse momentum correlator $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ is of particular interest for its potential sensitivity to the shear viscosity per unit of entropy density $\eta/s$ of the quark-gluon plasma formed in heavy-ion collisions [1,2]. We used the UrQMD, AMPT, and EPOS models at $\sqrt{s_{_{NN}}}$ 2760 and 200 GeV to investigate: the longitudinal broadening as well as the long range azimuthal dependence of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator. We will present the centrality, $\eta/s$, and the event shape dependence of the longitudinal width $\sigma\left( \Delta\eta \right)$ and the azimuthal harmonics $a^{p_T}_{n}$ of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator [3]. Our calculations showed that $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator can differentiate between theoretical models and constrain the determination of $\eta/s$.
[1] S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97, 162302 (2006)
[2] V. Gonzalez, et al., (2020), Eur.Phys.J.C 81 (2021) 5, 465
[3] Niseem Magdy, et al., arXiv:2105.07912
Various measurements on long-range correlation among produced particles from small collision systems indicate that there are collective flow phenomena in these systems. Previously, PHENIX published elliptic and triangular flow results in $p$+Au, $d$+Au, and $^{3}$He+Au collisions of different initial geometry which are well described by hydrodynamics. A new independent analysis has been performed using the two-particle correlation method and obtained consistent elliptic and triangular flow with the previous results. In addition, the analysis is extended to various detector combinations to understand non-flow effects and longitudinal decorrelations, both of which can affect flow measurements. In this presentation, new PHENIX results of elliptic and triangular flow in $p$/$d$/$^{3}$He+Au collisions at $\sqrt{s_{NN}}=200~\mathrm{GeV}$ will be presented, and the kinematic dependence will be discussed.
A primary aim of current nuclear science research at RHIC and the LHC is to delineate the normal and anomalous transport properties of the QGP produced in ion-ion collisions. I will show that the comprehensive RHIC and LHC data sets for different beam energies and collision systems in tandem with novel correlators and scaling functions provide unique insight into the transport properties of the QCD-matter created in small and large systems. I will also present specific testable predictions for future anisotropy measurements in small systems such as O+O at RHIC (0.20 TeV) and LHC (7.0 TeV), derived from the scaling functions.
We report the first measurement of the rapidity-odd directed flow ($v_1$) of multi-strange baryons ($\Xi$ and $\Omega$) in Au+Au collisions as recorded by the STAR detector at the Relativistic Heavy Ion Collider.
We focus on particle species where all constituent quarks are produced, as opposed to possibly transported, and demonstrate using a novel analysis method that the coalescence sum rule holds for hadrons with identical quark content. We examine the coalescence sum rule as a function of rapidity for non-identical quark content having the same mass but different strangeness ($\Delta S$) and electric charge ($\Delta q$). The difference in the directed flow of different quark and anti-quark combinations, e.g., $v_1(\Omega^{-}(sss)) - v_1(\bar{\Omega}^{+}(\bar{s}\bar{s}\bar{s}))$, is a measure of coalescence sum rule violation, and we call it directed flow splitting ($\Delta v_1$) between quarks and anti-quarks. This measurement uses the latest high statistics data sample from $\sqrt{s_{NN}}=$ 27 GeV Au+Au collisions where we take advantage of the improved event plane resolution of recently installed Event-Plane Detector (EPD). We measure $v_1$ as a function of rapidity; and then $\Delta S$ and $\Delta q$ dependence of the $\Delta v_1$-slope between produced quarks and anti-quarks in Au+Au collisions at $\sqrt {s_{NN}} =$ 27 GeV and 200 GeV. The $\Delta v_1$-slope increases when $\Delta S$ and $\Delta q$ increase. This $\Delta v_1$-slope signal becomes weaker going from collision energy$\sqrt{s_{NN}}=$ 27 GeV to 200 GeV. We compare our measurements with the Parton-Hadron String Dynamics (PHSD) model + EM-field calculations.
Rapidity-odd directed flow ($v_{1}$) of identified hadrons ($\pi^{\pm}$, $K^{\pm}$, $p$, $\overline{p}$, $\phi$, $\Lambda$, $\overline{\Lambda}$, $\overline{\Xi}^{+}$, $\Omega^{-}$ and $\overline{\Omega}^{+}$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 14.5, 27, 54.4 and 200 GeV using the AMPT model with the new quark coalescence is analyzed. A new method to test the Coalescence Sum Rule (CSR) or the Number of Constituent Quark (NCQ) scaling is also proposed by using the $v_{1}$ of produced identified hadrons ($K^{-}$, $\overline{p}$, $\overline{\Lambda}$, $\phi$, $\overline{\Xi}^{+}$, $\Omega^{-}$ and $\overline{\Omega}^{+}$). The CSR holds for the identical constituent quark combinations of produced hadrons. However, the sum rule is violated for non-identical quarks combination having the same mass but different strange ($\Delta S$) and electric charge ($\Delta q$) of the constituent quark. The difference in $v_{1}$ of quark and anti-quark obtained from the combination of produced hadrons as a function of rapidity is the measure of CSR violation quantified by the $\Delta v_{1}$-slope, [d($\Delta v_{1}$)/dy]. The $\Delta v_{1}$-slope as a function of strangeness difference is found to have strong energy dependence, with higher values at lower energies. The finding indicates that CSR is violated the most at low energies and has a strong strangeness dependent unlike the electric charge. The calculation performed by taking the primordial hadrons are consistent with the results of final state hadrons, which suggests that hadron scatterings and resonance decays do not much affect the sum rule. Hence, the coalescence sum rule of produced hadrons is more affected by the strong (QCD) force than the electromagnetic (QED) interaction.
To learn about the mechanism of particle production and phase changes from quarks to hadrons, fluctuations of observables from experiments are studied. Scaling of the observables from these experiments can reveal the properties of the system created, as it expands from quark-gluon plasma phase to hadronic phase. One of such techniques is to study the scaling behaviour of the normalized factorial moments ($F_{q}$) of multiplicity fluctuations with the bin size resolution or the number of bins ($M$). A power-law behaviour of $F_{q}$ as function of number of bins ($M$), known as intermittency, is a signature of fluctuations of self-similar nature. The normalized factorial moments (NFM) of order q are observed to scale with second-order NFM with scaling exponent $\nu$ $\approx$ 1.304, for Ginzburg-Landau theory when studied for formalism with second-order phase transition. Intermittency analysis of low energy data has been studied extensively as it promises to identify the quark-hadron phase transition and associated critical point. Event-by-event intermittency analysis of toy Monte Carlo events is carried in the scenario of high multiplicity events, where the charged particle bin multiplicity is large. Dependence of NFM on the detector efficiencies and on the presence of fluctuations have been studied. NFMs are observed to be sensitive to any fluctuations of dynamical nature which appear as large local multiplicity fluctuations. With no physics in the toy Monte Carlo events the results presented here provide a baseline to the experimental results and clarity on application of detector efficiency corrections to the experimental data for analysis.
This talk gives an overview of the latest measurements of collective behavior in a variety of collision systems with the ATLAS detector at the LHC, including pp collisions at 13 TeV, Xe+Xe collisions at 5.44 TeV, and Pb+Pb collisions at 5.02 TeV. These include measurements of vn-[pT] correlations in Xe+Xe and Pb+Pb, which carry important information about the initial-state geometry of the Quark-Gluon Plasma and can potentially shed light on any quadrupole deformation in the Xe nucleus; measurements of flow decorrelations differential in rapidity, which probe the longitudinal structure of the colliding system; and measurements of the sensitivity of collective behavior in $pp$ collisions to the presence of jets, which seek to distinguish the role that semi-hard processes play in the origin of these phenomena in small systems. These measurements furthermore provide stringent tests of the theoretical understanding of the initial state in heavy ion collisions.
The structure of hadrons relevant for deep-inelastic scattering are completely characterised by the Compton amplitude. As a physical amplitude, the Compton tensor is parameterised by structure functions and it naturally includes all target mass corrections and higher twist effects at a fixed virtuality, $Q^2$.
In this talk, I will be highlighting QCDSF/UKQCD Collaboration's recent developments on computing the Compton amplitude in a lattice approach. I briefly discuss how to access the Compton amplitude directly via the second-order Feynman-Hellmann theorem and as an application, present a calculation of the nucleon Compton tensor across a range of photon momenta. This enables us to study the $Q^2$ dependence of the low moments of the nucleon structure functions in a lattice calculation for the first time. I will also discuss possible further applications of this approach and present some preliminary results.
We consider the production of electroweak Z or $W^\pm$ bosons associated with $J/\psi$ mesons at the LHC conditions. Our attention is focused on new partonic subprocesses which yet have never been considered in the literature, namely, the charmed or strange quark excitation subprocesses followed by the charmed quark fragmentation $c\to J/\psi+c$. Additionally we take into account the effects of multiple quark and gluon radiation in the initial and final states with subsequent fragmentation. We find that the contributions from the new mechanisms are important and significantly reduce the gap between the theoretical and experimental results on the $J/\psi + Z$ and $J/\psi + W^\pm$ production cross sections.
Basis light-front quantization (BLFQ) provides a nonperturbative framework for solving relativistic many-body bound state problems in quantum field theories. We report our recent progress in applying BLFQ to illuminating structure of the meson and the baryon. We present our results on the meson spectra and other observables such as electromagnetic form factors, PDFs, GPDs and TMDs of the pion and the nucleon, where one dynamical gluon is retained for these systems.
B anomalies attract a lot of attention in the last few years. In the charged current caused ratios of the taounic semileptonic B decays to D() and the muonic one indicate deviations from the standard model prediction. In the case of flavour changing neutral current processes ratio of muonic and electronic in B to K() transitions and similar transitions of b to s l+ l- in variety of decays again there are deviations of measured and theoretically predicted values. In both anomalies the differences are on the level 3 to 4 standard deviations. Both anomalies are usually explained by the presence of new particles. I will review existing proposals of new physics and their consequences on theoretical and experimental studies.
Di-Jet angular correlations serve as a sensitive probe of saturation physics in the Color Glass Condensate (CGC), an effective theory of QCD in which a heavy target nucleus can be modeled as a classical background field. The leading order cross section for di-jet production in Deep Inelastic Scattering (DIS) is well known, but experiments at the Electron Ion Collider will be sensitive to corrections. Here we present our preliminary results for the calculation of Next to Leading Order (NLO) corrections to di-jet production in DIS at small Bjorken x, where the target nucleus is treated as a CGC. The Wilson line correlators are averaged according to the gaussian (MV) model, and we use the spinor helicity formalism for efficient calculation of the helicity structure.
We consider a method for determining the QCD strong coupling constant
using fits of perturbative predictions for event shape averages to data
collected at the LEP, PETRA, PEP and TRISTAN colliders. To obtain highest
accuracy predictions we use a combination of perturbative ${\cal{O}}(\alpha_{S}^{3})$
calculations and estimations of the ${\cal{O}}(\alpha_{S}^{4})$ perturbative
coefficients from data. We account for non-perturbative effects using modern
Monte Carlo event generators and analytic hadronization models.
The obtained results show that the total precision of the $\alpha_{S}$
determination cannot be improved significantly with the higher order perturbative QCD
corrections alone, but primarily requires a deeper understanding of the non-perturbative effects.
Calculations of Drell-Yan production at next-to-leading (NLO) order have been combined with transverse Momentum Dependent (TMD) distributions obtained with the Parton Branching (PB). For the first time, the predictions show a remarkable agreement with DY measurements across a wide range of DY mass and center of mass energies, from experiments like NuSea, R209, Phenix, CMS and ATLAS. Uncertainties from the TMD fit and from missing higher orders in the calculation are also determined. We also show predictions for Z+jet and multijet measurements, where especially angular correlations, sensitive to TMDs, are well described. We show that the PB TMDs together with a PB TMD parton shower and higher order matrix elements allow a very good description of measurements over a wide kinematic range.
Abstract: Invariant inclusive single-particle/jet cross sections in p–p collisions can be factorized in terms of two separable pT dependences, a [pT-√s] sector and an [xR-pT-√s] sector. We have analyzed data from ATLAS, CMS and LHCb to explore various s-dependent attributes and other systematics of inclusive jet, photon and single particle productions. Approximate power laws in √s, pT and xR, are found when we boost the kinematics by √s → ∞ for finite pT, using the radial scaling variable, x_R=(x_T^2+x_F^2\ )^(1/2). We show that the A(√s, pT) function, introduced in our earlier publication to describe the pT dependence of the inclusive cross section[1], is directly related to the underlying hard parton–parton scattering for jet production, with little influence from soft physics. In addition to the A-function, we introduce the F(√s, xR) function that obeys radial scaling for inclusive jets and offers another test of the underlying parton physics. An application to heavy ion physics is given, where we use our variables to determine the transparency of cold nuclear matter to penetrating heavy mesons through the lead nucleus in pA collisions.
In deeply inelastic lepton-nucleus scattering, hadron-nucleus and heavy-ion collisions, multiple scatterings of energetic partons in the nuclear medium lead to a broadening of the average jet transverse momentum. This jet broadening phenomenon offers a useful tool for probing the properties of nuclear media, including the quark-gluon plasma formed in high-energy heavy-ion collisions. Many theoretical frameworks have been developed in the study of multiple scatterings and their subsequent effects. We will focus on the collisional and radiative parton energy loss formalisms, as well as the higher-twist collinear factorization framework. In this talk, we present predictions for the jet broadening in heavy-ion collisions calculated using the Djordjevic-Gyulassy-Levai-Vitev (DGLV) energy loss model. DGLV assumes a factorization of the hard production process and the subsequent jet evolution in medium. As the next step, we will compute the transverse momentum jet broadening in semi-inclusive deep inelastic scattering (SIDIS) at Twist-4 where factorization is not assumed but appears to hold. The Twist-4 derivation includes cross talk between the production and evolution that is missing in the energy loss formalisms; we aim to quantify the importance of these neglected terms in energy loss calculations and, ultimately, to derive energy loss formulae that respect a rigorous factorization.
A dedicated session for talks which don't unambiguously fit into the dedicated tracks
Despite being the overwhelming majority of events produced in
hadron or heavy ion collisions, minimum bias events do not enjoy a robust
first-principles theoretical description as their dynamics are dominated
by low-energy quantum chromodynamics. In this talk, I will present a novel
expansion scheme of the cross section for minimum bias events in the large
number of detected particles N >> 1. I will identify power counting rules
and symmetries of minimum bias from which the form of the squared matrix
element can be expanded in irreducible symmetric polynomials of the phase
space coordinates. As two applications of this expansion, the single-
particle transverse momentum spectrum in pp collisions can be described by
a one-parameter distribution and the constraint of positivity of the
squared matrix element forces all azimuthal correlations in heavy ion
collisions vanish in the N → ∞ limit, as observed in data.
Recent developments of the model of quantized helical QCD string
are presented, notably the baryon production. An overview
of the experimental evidence and the progress in
the model implementation in Monte-Carlo simulation are discussed.
The ALICE collaboration at the large hadron collider recently reported high-statistics pt spectra from 5 TeV and 13 TeV p-p collisions. Particle data for each energy were partitioned into event classes based on the total yields within two disjoint pseudorapidity intervals denoted by acronyms V0M and SPD. For each collision energy spectra resulting from the two selection methods were then compared to a minimum-bias average over the entire event population. The nominal goal was determination of the role of jets in high-multiplicity p-p collisions and especially the jet contribution to the low-pt parts of spectra. A related motivation was response to recent claims of "collective" behavior and other nominal indicators of quark-gluon plasma (QGP) formation in small collision systems. In the present study a two-component (soft + hard) model (TCM) of hadron production in p-p collisions is applied to the ALICE spectrum data. As in previous TCM studies of a variety of A-B collision systems the jet and nonjet contributions to p-p pt spectra are accurately separated over the entire pt acceptance. The statistical significance of data-model differences is established leading to new insights concerning selection bias of V0M and SPD acceptances. The effect of spherocity (azimuthal asymmetry measure nominally sensitive to jet production) on ensemble-mean pt vs event multiplicity nch is investigated and an ironic result emerges.
Quark-gluon plasma (QGP) was discovered in heavy ion collisions at Relativistic Heavy Ion Collider. Later the formation of the QGP was confirmed by the Large Hadron Collider at much higher energies. Although QGP existence might be beyond doubt, its properties nowadays are the subject of detailed systematic study.
Strange quarks are absent in the colliding heavy ions and can only be formed in the QGP. Hence, measurements of strange quarks is a good way to explore QGP properties. Particles which contain strange quarks can be a great tool to study parton recombination at intermediate transverse momentum (pT) and energy loss at high pT.
In this talk, we will present the most recent PHENIX results on nuclear modification factors of K+-, phi, K*0 mesons as function of pT and number of participants in p+p, p+Al, p+Au, d+Au, He+Au, Cu+Cu, Cu+Au, Au+Au, and U+U collision systems. These results are aimed to enrich the understanding of strange(hidden strange) particle production and its difference from the production of particles which do not contain strange quarks.
Exclusive photoproduction of $\rho^0(770)$ mesons is studied using the H1 detector at the $ep$ collider HERA. A sample of about 900000 events is used to measure single- and double-differential cross sections for the reaction $\gamma{}p\to \pi^{+}\pi^{-}Y$. Reactions where the proton stays intact ($m_Y=m_p$) are statistically separated from those where the proton dissociates to a low-mass hadronic system ($m_p<{}m_Y<{}10$ GeV). The double-differential cross sections are measured as a function of the invariant mass $m_{\pi\pi}$ of the decay pions and the squared $4$-momentum transfer $t$ at the proton vertex. The measurements are presented in various bins of the photon-proton collision energy $W_{\gamma{}p}$. The phase space restrictions are $0.5<{}m_{\pi\pi}<{}2.2$ GeV, $\vert{}t\vert<{}1.5$ GeV$^2$, and $20<{}W_{\gamma{}p}<{}80$ GeV. Cross section measurements are presented for both elastic and proton-dissociative scattering. The observed cross section dependencies are described by analytic functions. Parametrising the $m_{\pi\pi}$ dependence with resonant and non-resonant contributions added at the amplitude level leads to a measurement of the $\rho^0(770)$ meson mass and width at $m_\rho=770.8^{+2.6}_{-2.7}$ (tot) MeV and $\Gamma_\rho=151.3^{+2.7}_{-3.6}$v (tot) MeV, respectively. The model is used to extract the $\rho^0(770)$ contribution to the $\pi^{+}\pi^{-}$ cross sections and measure it as a function of $t$ and $W_{\gamma{}p}$. In a Regge asymptotic limit in which one Regge trajectory $\alpha(t)$ dominates, the intercept $\alpha(t{=}0)=1.0654^{+0.0098}_{-0.0067}$ (tot) and the slope $\alpha^\prime(t{=}0)=0.233^{+0.067}_{-0.074}$ (tot) GeV$^{-2}$ of the $t$ dependence are extracted for the case $m_Y{=}m_p$.
Eur.Phys.J.C80 (2020), 1189
Recent results of soft and small-x QCD measurements with the CMS experiment, such as minimum bias/underlying event physics, Double Parton Scattering and forward jet production.
Photon-photon fusion is a rare process at hadron and ion colliders. It is particularly interesting as a remarkably clean interaction with little (if any) remnant activity from the interacting particles. In this talk we present the status of photon-photon fusion measurements at the ATLAS detector. We present differential measurements of the light-by-light scattering process, γγ → γγ, in lead-lead collisions. In addition, we present photon-photon fusion measurements using events that contain two charged leptons in the final state. The scattered proton is detected by the ATLAS Forward Proton spectrometer while the leptons are reconstructed by the central ATLAS detector. Finally, we highlight the observation of photon-induced $WW$ production.
The light-front holography or light-front AdS/QCD is defined as a connection between light-front QCD and the description of hadronic modes on AdS spacetime. This relation, inspired in the AdS/CFT correspondence, has shown improvements in analytic solutions in the hadron physics regime.
We are motivated by the light-front AdS/QCD prediction on a general form of two particle bound state wave function inside nucleons. Diquark degrees-of-freedom within the framework of a quark model have been suggested also in the baryon structure in lattice-QCD as well as in phenomenological resources to study observed data.
This fact has motivated studies of nucleon models considering diquarks in their valence structure, the so called quark-diquark nucleon models. One of these studies has been shown light-front wave functions QCD matched with light-front AdS/QCD predictions. From such result, followed a model that contemplates the scale evolution of the Parton Distribution Functions (PDFs) for a quark-diquark nucleon model using scale dependent parameters following the DGLAP evolution.
Based on these results, we have performed a calculation of the PDF parameters constructed on the so called AdS/QCD quark-diquark nucleon model from the available data from NNPDF collaboration for u and d quarks, in order to get the unpolarized PDFs for the scalar and axial-vector diquarks in protons and neutrons. The PDFs obtained are expected to be used in nucleon and heavy-ion collision simulations to study the role of valence-diquark hard-processes on hadron production.
Multiparticle correlations measurements in even the smallest collision systems are consistent with predictions from viscous relativistic hydrodynamics calculations. However, these hydrodynamics calculations use a continuum extrapolated---i.e. infinite volume---equation of state. For the modest temperature probed in these small collisions, the controlling dimensionless product of the temperature and system size T*L ~ 400 MeV * 2 fm / 197 MeV fm ~ 4 is not particularly large. One should therefore investigate the small system size corrections to the equilibrium QCD equation of state used in modern viscous hydrodynamics simulations.
We present first results on just such finite system size corrections to the equation of state, trace anomaly, and speed of sound for two model systems: 1) free, massless scalar theory and 2) quenched QCD with periodic boundary conditions (PBC). We further present work-in-progress results for quenched QCD with Dirichlet boundary conditions.
We show that free, massless scalar fields, which are maximally sensitive to the finite size box, deviate enormously from their infinite volume conformal limit. Quenched QCD with PBC show corrections of ~20% for the trace anomaly near the phase transition. These corrections are more modest, but will have a meaningful, quantitative impact on the extracted bulk and shear viscosities in these small systems.
This presentation is based on
Mogliacci et al., Phys.Rev.D 102 (2020) 11, 116017 [arXiv:1807.07871]
Kitazawa et al., Phys.Rev.D 99 (2019) 9, 094507 [arXiv:1904.00241]
Horowitz and Rothkopf, in progress
We present a new release of the NNPDF family of global analyses of the proton's parton distribution functions: NNPDF4.0. It includes a wealth of new experimental data from HERA and the LHC, from dijet cross-sections and isolated photons to single-top and top-quark pair differential distributions. The NNPDF4.0 methodology benefits from improved machine learning algorithms, in particular automated hyperparameter optimisation and stochastic gradient descent for neural network training, which has been validated extensively by means of closure tests and future tests. We demonstrate the stability of the results with respect to the choice of parameterisation basis. We compare NNPDF4.0 with its predecessor NNPDF3.1 as well as to other recent global fits, and study its phenomenological implications for representative collider observables. We assess the impact of representative datasets on specific PDF flavour combinations, such as the dijet and top quark data on the gluon, the Drell-Yan and neutrino DIS data on strangeness, and electroweak measurements on charm and quark flavour separation.
Lattice QCD (LQCD) is a theoretical non-perturbative approach for the study of QCD dynamics numerically from first principles. LQCD is widely used for hadron structure calculations and is becoming a reliable tool, striving for control of various sources of systematic uncertainties. Parton distribution functions (PDFs) have a central role in understanding hadron structure and have been calculated in lattice QCD mainly via their Mellin moments. In this talk, we will present results for alternative new methods to access PDFs that rely on matrix elements of fast-moving hadrons coupled to non-local operators. The main focus of the talk is to demonstrate the successes and challenges in these approaches using recent results for PDFs and GPDs. Future perspectives will also be discussed.
The quark-gluon dynamics manifests itself in a set of non-perturbative functions describing all possible spin-spin and spin-orbit correlations. The Transverse Momentum Dependent parton distributions (TMDs) and Generalized Parton Distributions (GPDs) carry information not only on the longitudinal but also on the transverse momentum and position of partons, providing rich and direct information on the orbital motion of quarks. Single and Dihadron semi-inclusive and hard exclusive production, both in current and target fragmentation regions, provide a variety of spin and azimuthal angle dependent observables, sensitive to the dynamics of quark-gluon interactions. Studies of the 3D PDFs are currently driving the upgrades of several existing facilities (JLab, COMPASS and RHIC), and the design and construction of new facilities worldwide (EIC, FAIR, and JPARC).
In this talk, we present an overview of the current status and some future measurements of the orbital structure of nucleons at Jefferson Lab.
The Pierre Auger Observatory is the largest facility in the world to observe ultra-high-energy cosmic rays. It has a hybrid detection technique which combines the observation of the longitudinal development of the shower of secondary particles produced in the atmosphere by the cosmic primary and the measurement of particles at ground. This has allowed the Auger Collaboration to produce results regarding the energy spectrum, mass composition and arrival directions of ultra-high-energy cosmic rays with unprecedented precision. But it also opened the possibility to study hadronic interactions taking place at energies well beyond those accessible by human-made accelerators and, therefore, probe current models tuned to LHC data.
In this report, we present a selection of the latest results on hadronic interactions with measurements from the Pierre Auger Observatory, over three decades at the highest energies, showing the tension between data from the muonic component of air-showers and predictions based on the most updated hadronic models.
Next generation neutrino experiments will push the limits in our understanding of astroparticle physics in the neutrino sector to energies orders of magnitude higher than the current state-of-the-art high-energy neutrino experiment, IceCube. These experiments will use neutrinos to tell us about the most extreme environments in the universe, while simultaneously leveraging these extreme environments as probes of neutrino properties at the highest energies accessible in the foreseeable future: $E\sim10^9$ GeV. At these energies neutrinos are readily absorbed in the Earth. Assuming an isotropic distribution, by looking at how the flux varies as a function of angle through the Earth, we show that it is possible to extract the $\nu_\tau-N$ cross section with precision at the $\sim$20% level (1$\sigma$ assuming Wilks' theorem) given $N_{\rm events}\sim$100 events.
The Giant Radio Array for Neutrino Detection (GRAND) is designed to detect ultra-high-energy cosmic particles — specially neutrinos, cosmic rays and gamma-rays using radio antennas. On its final design, the radio array will contain 200,000 antennas and cover a total area of 200,000 km$^{2}$ split in $\sim$20 montainous sites spread worldwide. The detection strategy is based on the coherent radio emission (in the 50-200 MHz range) produced by the extensive air showers (with energis above 10$^{17}$eV) induced in the atmosfere by the cosmic particles. Regarding neutrinos, the study is two-fold. In astronomy, the planned sensitivity of 10$^{-10}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ above $5\times10^{17}$ eV will likely ensure the detection of "cosmogenic" neutrinos that are produced in the most common scenarios. In particle physics, PeV–EeV neutrinos can test particle interactions at energies above those achieved in accelerators at Earth. Furthermore, with baselines between megaparsecs and a few gigaparsecs, even tiny new‑physics effects could accumulate during propagation and reach detectable levels. GRANDProto300, the 300-antenna pathfinder array, is planned to start taking data in 2021. It aims at demonstrating autonomous radio detection of inclined air-showers, and study cosmic rays around the transition between Galactic and extra- Galactic sources. We present the current overall status of the project and simulation results that support the science case.
Charged pions, which obviously carry no baryon number, possess, however, a nontrivial baryonic structure, stemming from the isospin breaking with the up and down quark mass splitting and the EM effects. We obtain estimates for the corresponding pion baryonic (vector isoscalar) form factor in two ways: from simple constituent quark models on one hand, and from vector meson dominance model fits to the e+e- → π+π- data on the other hand. All our estimates yield a positive baryon mean square radius of pi+, in the range (0.03 − 0.04 fm)^2. Hence, a picture emerges where the outer spatial region of pi+ has a net baryon density (u excess), and the inner region a net antibaryon density (d-bar excess), both compensating each other such that the total baryon number is zero. For π− the effect is equal and opposite. We also discuss the challenging lattice QCD prospects of measuring this fundamental property of the pion.
Based on 2103.09131 [hep-ph]
Medium-induced gluon radiation is known to be an important tool to extract the properties of the QGP created in heavy-ion collisions. I will use a recent approach to evaluate the full in-medium gluon emission spectrum, including the resummation of all multiple scatterings, to analyze the validity of the usually employed analytical approximations. More specifically, by using this all-order result I will determine the kinematic regions in which the effects of multiple scatterings are essential and where, in contrast, a single hard scattering is enough to describe the in-medium emission process. Furthermore, I will compute the effects due to the inclusion of a time delay in the production of the medium has on the emission spectrum.
We consider the hadronization of the deconfined matter arising in high-energy particle collisions, based on the quark-hadron duality concept. The number of generated hadrons is shown to be entirely determined by the exact non-equilibrium Green's functions of partons in the deconfined matter and the vertex function governed by the probability of the confinement-deconfinement phase transition.
Compactifying the standard (3+1) chromodynamics into $ QCD_{2} + QCD_{2}$, the rate of hadrons produced in particle collisions with respect to both the rapidity and $p_T$ distributions is derived in the flux tube approach. Provided that the hadronization is the first order phase transition, we obtain the hadron rate in the explicit form. The derived rate turns out to be strongly dependent on the energy of colliding particles, the number of tubes, the hadron mass as well as on the temperature of the confinement-deconfinement phase transition. In the case of pion production in $pp$ collisions we obtain a good agreement to the experimental results on the pion yield with respect to both the rapidity and $p_T$ distributions.
Briefly after the Big Bang, the early universe was in a high temperature and high density environment. In order to recreate this state of matter in the laboratory, mini bangs are created by colliding heavy ions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory and subsequently at the Large Hadron Collider (LHC) at CERN. In this talk I shall be covering on the selected results from LHC and RHIC. I shall be covering spectra and correlations (flow) and also nuclear modification factor. I shall be discussing quarkonia flow in further detail. Due to the larger mass of the bottomonium states compared to the charmonium ones,the measurement of bottomonia production in proton-nucleus collisions allows a study of CNM effects in a different kinematic regime, therefore complementing the J/Psi studies[1]. For smaller systems like p+A and p+p we have less deeply bound bottomonia states and thus a comparatively larger chance to escape. This means that more states become measurable, which is a positive feature. On the other hand,it also means that the escape mechanism which underlies the anisotropic flow of bottomonia may become largely ineffective, in particular for the Upsilon(1S). Accordingly,the measurement of a sizable flow for Upsilon(1S) in small systems[2] would probably hint at the importance of initial-state correlations. Hence understanding small systems becomes very important and such studies will be also stressed and presented including the opportunities which will be possible in LHC Run-3 small system data-sets.
[1] D. Das and N. Dutta, Int. J. Mod. Phys. A 33, no. 16, 1850092 (2018)
[2] D.Das , Nucl.Phys.A 1007 (2021) 122132
Jet substructure, defined by observables constructed from the distribution of constituents within a jet, provides the versatility to tailor observables to specific regions of QCD radiation phase space. This flexibility provides exciting new opportunities to study jet quenching in heavy-ion collisions and to
ultimately help reveal the nature of the quark-gluon plasma. In this talk, we focus on the momentum fraction $z$ of reclustered subjets, which has recently been proposed to test the universality of jet fragmentation in the quark-gluon plasma, as well as to measure ''energy loss'' at the cross-section level.
Subjet fragmentation measurements are complementary to well-established measurements of the longitudinal momentum fraction of hadrons in jets, providing a new opportunity to study the relationship between hadrons and jets.
We report the first measurements of subjet fragmentation in both Pb-Pb and proton-proton collisions. These subjet measurements allow to extend to higher $z$ than with hadrons, enabling access to a quark-dominated sample of jets and exposing the interplay of soft medium-induced radiation with the relative suppression of quark vs. gluon jets. These measurements will be compared to theoretical calculations and contrasted with related jet substructure measurements, helping to elucidate the physics underlying jet quenching.
Recently, event shape observables such as transverse spherocity ($S_{0}$), has been studied successfully in small collision systems at the LHC as a tool to separate jetty and isotropic events. In our work, we have performed an extensive study of charged particles' azimuthal anisotropy in heavy-ion collisions as a function of $S_{0}$ for the first time using a multi-phase transport (AMPT) model. We have used the two-particle correlation (2PC) method to estimate the elliptic flow ($v_2$) for different centrality classes in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV for high-$S_0$, $S_{0}$-integrated and low-$S_0$ events. We found that transverse spherocity successfully differentiates heavy-ion collisions’ event topology based on their geometrical shapes {\em i.e.} high and low values of spherocity ($S_0$). The high-$S_0$ events are found to have nearly zero elliptic flow while the low-$S_0$ events contribute significantly to elliptic flow of spherocity-integrated events. It was found that the number of constituent quark scaling of elliptic flow is strongly violated in events with low-$S_0$ compared to $S_0$-integrated events. In the absence of experimental explorations in this direction, we implement a machine learning based regression method to estimate $S_0$ distributions in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV by training the model with experimentally available event properties. This method works well as a good agreement between the simulated true values and the predicted values from the ML-model is observed.
References:
1. N. Mallick, R. Sahoo, S. Tripathy and A. Ortiz, J. Phys. G48, 045104 (2021).
2. N. Mallick, S. Tripathy, A. N. Mishra, S. Deb and R. Sahoo, Phys. Rev. D103,094031 (2021).
3. N. Mallick, S. Tripathy and R. Sahoo, arXiv:2105.09770 [hep-ph].
The Belle II experiment at the SuperKEKB energy-asymmetric $e^+ e^-$ collider is an upgrade of the B factory facility at KEK in Tsukuba, Japan. The experiment began operation in 2019 and aims to record a factor of 50 times more data than its predecessor. Belle II is uniquely capable of studying the so-called "XYZ" particles: heavy exotic hadrons consisting of more than three quarks. First discovered by Belle, these now number in the dozens, and represent the emergence of a new category within quantum chromodynamics. We present recent results in new Belle II data, and the future prospects to explore both exotic and conventional quarkonium physics.
We study tetraquark states of all $qq\bar q\bar q$, $qc\bar q \bar c$, $sc\bar q \bar c$ and $cc\bar c \bar c$ ($q=u,d$ quark) quark configurations and all S-wave tetraquark masses are evaluated in a constituent quark model where the Cornell-like potential and one-gluon exchange spin-spin coupling are employed.
All model parameters are predetermined by comparing the theoretical and experimental masses of light, strange, charmed and bottom mesons.
The theoretical predictions of the tetraquarks are compared with the observed exotic meson states. Two tentative assignments for light and charmonium-like tetraquarks are suggested respectively.
The work suggests that the $X(6900)$ observed by LHCb is likely to be the first radial excited fully-charm tetraquark state with $J^{PC} = 0^{++}$ in the $\bar 3_c \otimes 3_c$ configuration, and the ground and second radial excited states of fully-charm tetraquark are around $6450MeV$ and $7250MeV$ respectively.
In this talk, we present the production measurements of $\Lambda_{\rm c}^{+}$, $\Xi^{0,+}_{\rm c}$, $\Sigma^{0,++}_{\rm c}$ and the first measurement of $\Omega_{\rm c}^{0}$ baryon performed with the ALICE detector at the midrapidity in pp collisions at $\sqrt s=$ 5.02 and 13 TeV. Recent results show that the baryon-to-meson ratios are significantly higher than those measured in $\rm e^{+}e^{-}$ collisions for the different charm-hadron species. These observations suggest that the fragmentation fractions of charm are not universal and that the baryon-to-meson ratio depends on the collision systems. The result will be compared to predictions from Monte Carlo event generators and theoretical calculations based on the statistical hadronization model and on the hadronization via coalescence. In addition, the measurements of charm fragmentation fractions and the charm total production cross section per unit of rapidity at midrapidity, in pp collisions at $\sqrt s=$ 5.02 TeV at the LHC will also be shown.
Hypernuclei are bound nuclear systems of nucleons and hyperons. As such, hypernuclei are correlated hyperon-baryon systems and therefore provide direct access to study the hyperon$-$nucleon (Y-N) interaction. Production of hypernuclei in heavy-ion collisions provides an experimental avenue for studying the Y-N interaction. $\Lambda$ hypernuclei, such as $^3_{\Lambda}H$ and $^4_{\Lambda}H$, are usually understood as a weakly bound system of a $\Lambda$ and a nucleus. According to this concept, the $\Lambda$ maintains its identity even if embedded in a system of other nucleons. Since the lifetime of a hypernucleus depends on the strength of the Y-N interaction, precise lifetime measurements of hypernuclei help us to understand the Y-N interaction.\
In this talk, we will present the first lifetime measurements of $^3_{\Lambda}H$ and $^4_{\Lambda}H$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.2 GeV, recorded by the STAR experiment with a fixed target mode in the year 2018.
NA61/SHINE is a fixed-target experiment at CERN Super Proton Synchrotron which goal is to explore the phase diagram of strongly interacting matter. A two-dimensional scan of this diagram is performed by varying the beam momentum (13A-150(8)A GeV/c) and the system size (p+p, Be+Be, Ar+Sc, Xe+La, Pb+Pb). The motivations of this measurements are the study of the properties of the onset of deconfinement and the search for the critical point of the strongly interacting matter. At the critical point the correlation length diverges, what causes the increase of fluctuations signal. In this contribution, fluctuation analysis methods used by NA61/SHINE, recent fluctuation results and its comparison with model predictions will be discussed.
The measurement of exclusive $e^+e^-$ to hadrons processes is a significant part of the physics program of $BABAR$ experiment, aimed to improve the calculation of the hadronic contribution to the muon $g−2$ and to study the intermediate dynamics of the processes. We present the most recent results obtained by using the full data set of about 470 $fb^{−1}$ collected by the BABAR detector at the PEP-II $e^+e^-$ collider at a center-of-mass energy of about 10.6 GeV. In particular, we report the results on $e^+e^-$ annihilation into six- and seven-pion final states. The study of the very rich dynamics of these processes can help to understand the difference seen between the QCD prediction and the sum of exclusive cross sections in the energy region around 2 GeV, thus improving the precision on the total hadronic cross section and of the g-2 calculation.
The study of medium-induced modifications to the substructure of inclusive charged jets indicates a redistribution of energy inside the jet cone and provides insight into the energy loss mechanisms of jets in the medium. The in-medium modification to two jet shape observables i.e., the differential jet shape ($\rho$(r)) and the angularity (g) in the most central Pb−Pb collisions at 2.76TeV has been investigated using JEWEL (recoil OFF) and EPOS-3 event generators in the jet-$p_{T}$ range of 20-40 GeV/c. Comparison between the results from these models shows that while JEWEL (recoil OFF) does not explain the distribution of lost energy at higher radii with respect to the jet-axis,EPOS-3 explains the effect quite well. However, in EPOS-3, the partonic energy loss mechanism and secondary hard-soft interactions during hadronization and hadronic cascade phase are different from the conventional jet energy loss models. This study can provide important new insights on mechanisms regarding the modeling of the medium and hard-soft interactions in heavy ion collisions.
The particle momentum anisotropy ($v_n$) produced in relativistic nuclear collisions is considered to be a response of the initial geometry or the spatial anisotropy $\epsilon_n$ of the system formed in these collisions. The linear correlation between $\epsilon_n$ and $v_n$ quantifies the efficiency at which the initial spatial eccentricity is converted to final momentum anisotropy in heavy ion collisions. We study the transverse momentum, collision centrality, and beam energy dependence of this correlation for different charged particles using a hydrodynamical model framework. The ($\epsilon_n -v_n$) correlation is found to be stronger for central collisions and also for n=2 compared to that for n=3 as expected.However, the transverse momentum ($p_T$) dependent correlation coefficient shows interesting features which strongly depends on the mass as well as $p_T$ of the emitted particle. The correlation strength is found to be larger for lighter particles in the lower $p_T$ region. We see that the relative fluctuation in anisotropic flow depends strongly on the value of $\eta/s$ specially in the region $p_T <1$ GeV unlike the correlation coefficient which does not show significant dependence on $\eta/s$.
NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) is a fixed-target experiment at the CERN Super Proton Synchrotron. One of its research projects is the systematic measurement of hadron production in proton+proton, proton+nucleus and nucleus+nucleus interactions. These studies are performed in particular to study the predicted signals of the onset of deconfinement and search for the critical point of strongly interacting matter. For this investigation a two dimensional scan in beam momentum (13$A$ -150$A$ GeV/$c$) and nuclear mass number of colliding nuclei was performed.
This contribution reviews recent results of NA61/SHINE on strange-hadron spectra in \textit{p+p} interactions at $\sqrt{s_{NN}}=17.3$ GeV. Recently published measurements on the production of charged kaons and several hyperons will be presented with the new results on $K^{0}_{S}$ mesons and $\Xi(1530)/\bar{\Xi}(1530)$ resonances. The NA61/SHINE results will be compared with other measurements and with predictions of various theoretical models, like EPOS, PHSD, SMASH, UrQMD and others.
We study hidden-charm pentaquarks in the molecule picture of charmed baryon and anticharm meson in the approach of quark model and group theory. The strong decay of $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ are calculated for all 18 quark configurations and 47 states. It is found that all the possible states for Pc can decay through the $NJ/\psi$ channel and $N\eta_c$ channel for J=1/2, while only five states decay dominantly through the open-charm decay channels.
In relativistic heavy ion collisions the number of participant nucleons fluctuates event-by-event due to the fluctuations in the nucleon positions around the mean nuclear density profile. This asymmetry causes a shift in the center-of-mass rapidity of the participant zone and is known as longitudinal asymmetry. We have studied the effect of the longitudinal asymmetry on charged particle rapidity distributions and flow coefficients for Cu+Cu and Au+Au collisions using the AMPT model at beam energies 200 and 62.4 AGeV and at different centrality bins. We see that the width of the rapidity shift distribution increases from central to peripheral collisions. The effect of longitudinal asymmetry can be related to the average rapidity shift by a third-order polynomial. The coefficients of this polynomial characterize the effect of the asymmetry and are proportional to the rapidity shift. The system size and energy dependence of the coefficients show that the longitudinal asymmetry is higher for smaller systems and also for lower collision energies. We show that the rapidity shift is quite significant for these systems and thus the inclusion of it is important for a precise estimation of the particle reproduction and anisotropic flow parameters from these collisions.
Spectra of dilepton pairs in ultraperipheral nuclear collisions
are calculated. It is shown that production of low-mass e+e- pairs is enhanced due to the Sommerfeld-Gamow-Sakharov (SGS) factor. This effect is especially strong near the threshold of creation of unbound pairs with low masses in the two-photon fusion. Coulomb attraction of the non-relativistic components of such pairs may lead to the increased intensity of 511 keV photons. It can be recorded
at the NICA collider and has some astrophysical implications.
The analogous effect can be observed at LHC in dilepton production.
In high energy scattering, multiproduction process is unique in its relevance to total cross section an in its global property such as rapidity distribution, etc. If there is hard interactions, the jet rate and structure is a good arena of perturbative chromodynamics. However, once any specific hadron is considered, The property and structure of the hadron must make sense while the global and/or perturbative chromodynamics mechanism still can put important constrains.
The relation of the property and structure of the hadron with its production cross section, distribution etc. is much more complex than its decay process. In one hand there are many difficulties and challenges in calculation; on the other hand, production process provide unique way to study the details of property and structure of the hadron, which is beyond the approach of its decay process.
In this talk I will review our works on such topic in recent years, mainly on the multiquark state (e.g., XYZ particles) production in multiproduction process and the Bethe-Salpeter wave function in exclusive process. For the multiquark state production in multiproduction process, I will emphasize on the unitarity of hadronization process (and relevant models) and discuss why until now, No multiquark states (except the the unclear X(3872)) is observed to produce in multiproduction process. I will also discuss how to calculate hadron molecule production in multiproduction process.
Some of the Refs.
1, Exclusive production ratio of neutral to charged kaon pair in e^+e^- annihilation continuum via a relativistic quark model
Phys.Rev.C 102 (2020) 1, 015201 • e-Print: 1906.11575 [hep-ph]
2, Exotic hadron bound state production at hadron colliders
Chin.Phys.C 41 (2017) 8, 083106 • e-Print: 1610.04411 [hep-ph]
3, New Bs0π± and Ds±π± states in high energy multiproduction process
Phys.Rev.D 94 (2016) 1, 014023 • e-Print: 1603.03250 [hep-ph]
4, Unitarity and Entropy Change in Exclusive Quark Combination Models
e-Print: 1005.4664 [hep-ph]
5, Exotic hadron production in quark combination model
Phys.Rev.C 80 (2009) 035202 • e-Print: 0906.2473 [hep-ph]
6, Generalized structure of hadron-quark vertex function in Bethe- Salpeter framework: Applications to leptonic decays of V-mesons
J.Phys. 32 (2006) 949-961 • e-Print: hep-ph/0512352 [hep-ph]
The existence of topological solutions of the Standard Model field equations has been established since the 70ies. In Quantum Chromodynamics, these "Instanton transitions" are known to play a fundamental role in the long-distance behaviour of the theory, yet direct experimental evidence of these phenomena is still lacking. This raises the question of whether these processes could be observed at current or future high-energy colliders. In this contribution the signatures of Instanton induced processes at hadron colliders will be discussed, and different search strategies aiming to disentangle the contribution of QCD Instantons from the large background from other QCD processes will be presented. First upper limits on the Instanton production cross-section have been derived from published LHC data, as well as the expected sensitivities from future targeted searches at the LHC and HL-LHC.
Studies of identical-particle correlations started with radio astronomy and later with correlations of identical pions in proton-antiproton collisions. These measurements, more generally called femtoscopy, can be used to investigate the space-time dimensions of the region from which the particles are emitted. However the method applied to high energy collisions is sensitive not only to quantum statistics, but also to final state interactions, such as Coulomb interactions when considering charged particles and strong interactions between hadrons. The lack of numerical description of meson-meson correlations motivated the development of a code that solves the Lippmann-Schwinger equation and then obtain the scattered wave functions considering non-local potentials, and afterwards the respective two-particle correlation function. In particular, this procedure is used to investigate the sensitivity of the strong interaction to different source sizes. This numerical solution was applied to the $D^{0}$ mesons ($D^{0}D^{0}$ and $\overline{D}^{0}\overline{D}^{0}$) systems, for which experimental data is yet not available.
In an extension to our previous work where we established that the intermittency-type fluctuations as outlined by Bialas and Peschanski in the 1980s is present at √s = 7 TeV, the analysis is continued to include more energies from Run 1 data from the CMS collaboration at CERN. A preliminary look into how the slope parameters in the bin-averaged scaled factorial moments vary with collision energy at the TeV scale is presented, and we outline possible areas planned for future studies.
Oscillations in modified combinants (C j s) have been of interest to multiparticle production mechanisms since the 1990s. Recently, there has been a discussion on how such oscillations can be reproduced by compounding a binomial distribution with a negative binomial distribution. In this work, we explore a stochastic branching model based on a simple interaction term Aφ ∗ φ for partons and propose a hadronization scheme to arrive at the final multiplicity distribution. We study the effects that compounding our model with a binomial distribution has on C j s and explore its physical implications.
We present a discussion on recent progress in high energy diffraction from the perspective of AdS/CFT, through which a unified treatment for both perturbative and non-perturbative Pomeron emerges. By working with unitary irreducible representation of conformal group, a frame is provided in extending AdS/CFT to both forward and near-forward scattering. We present an analysis involving an exact solution to conformal blocks in Minkowski CFT and discuss possible applications. Phenomenological applications can range from forward scattering to DIS/DVCS/TMD at LHC energies and beyond.
The production of $W/Z$-bosons in association with jets is an important test of perturbative QCD predictions and also yields information about the parton distribution functions (PDFs) of the proton. The latest results of differential cross-section measurements for Z-boson production in association with jets (including heavy flavour) from the ATLAS experiment at the LHC will be presented. The measurements are corrected for detector inefficiency and resolution and the results are compared to state-of-the-art theory predictions, indicating several interesting discrepancies. We also present fits to determine PDFs using inclusive $W/Z$-boson and $W/Z$+jets measurements from ATLAS. The ATLAS measurements are used in combination with deep-inelastic scattering data from HERA. An improved determination of the sea-quark densities at high Bjorken $x$ is seen, while confirming a strange-quark density similar in size to the up- and down-sea-quark densities in the range $x < 0.02$ found by previous ATLAS analyses.
Recent measurements of tree-level $b\to c\ell\nu$ and loop-level $b\to s \ell^{+}\ell^{-}$ decays show an intriguing and consistent pattern of tensions between measured observables and Standard Model predictions. These tensions are referred to collectively as the flavour anomalies. This talk outlines the current experimental status of the flavour anomalies, with particular focus on measurements for which better understanding of hadronic effects is central to determining the underlying source of observed deviations.
B anomalies attract a lot of attention in the last few years. The charged current caused ratios of the taounic semileptonic B decays to D() and the muonic one indicate deviations from the standard model prediction. In the case of flavor changing neutral current processes ratio of muonic and electronic in B to K() transitions and similar transitions of b to s l+ l- in various decays again, there are deviations of measured and theoretically predicted values. In both anomalies, the differences are on the level 3 to 4 standard deviations. The presence of new particles usually explains both anomalies. I will review existing proposals of new physics and their consequences on theoretical and experimental studies.
The Belle II experiment at the SuperKEKB energy-asymmetric e+e− collider is a substantial upgrade of the B factory facility at the Japanese KEK laboratory. The target luminosity of the machine is $6\times10^{35}$ cm$^{−2}$s$^{−1}$ and the Belle II experiment aims to record 50 ab$^{−1}$ of data, a factor of 50 more than its predecessor. With this data set, Belle II will be able to measure the Cabibbo-Kobayashi-Maskawa (CKM) matrix, the matrix elements and their phases, with unprecedented precision and explore flavor physics with B and charmed mesons, and τ leptons. Belle II has also a unique capability to search for low mass dark matter and low mass mediators. We also expect exciting results in quarkonium physics with Belle II. In this presentation, we will review the status of the Belle II detector, the results of the planned measurements with the full available Belle II data set, and the prospects for physics at Belle II.
The pre-equilibrium stage of quark-gluon plasma remains one of the major sources of uncertainty in studies of heavy ion collisions, which became a prominent research problem in heavy ion community. Major efforts regarding this problem are made in low-$p_\perp$ sector. We here instead propose [1] to utilize high-$p_{\perp}$ particles energy loss, as a complementary tool, to elucidate these early stages.
To this end, we employ our recently developed DREENA-B framework, which is based on our sophisticated dynamical energy loss formalism, where temperature is an intrinsic input/parameter. It also considers a simple Bjorken medium evolution, which is highly suitable for analytically exploring different energy loss scenarios. Within this, we test four distinct cases, ranging from none to infinitely large energy loss in pre-equilibrium stage. In particular, we test: 1) free-streaming case; 2) linear case, corresponding to linearly increasing temperature with time; 3) constant case, with constant pre-equilibrium temperature; and 4) divergent case, corresponding to Bjorken expansion from the beginning. Thus obtained high-$p_\perp$ $R_{AA}$ and $v_2$ predictions for $h^{\pm}$, $D$ and $B$ mesons are compared with 5.02 TeV LHC data. Contrary to common expectations, we obtain that high-$p_\perp$ $v_2$ is unable to distinguish between diverse scenarios, being insensitive to the early stages of medium evolution. $R_{AA}$ is however sensitive to these different cases, and could provide an insight in the early stages' dynamics. However, higher-precision measurements of high-$p_\perp$ $R_{AA}$ are required to allow for more reliable conclusions through this observable.
[1] D. Zigic, B. Ilic, M. Djordjevic and M. Djordjevic, Phys. Rev. C 101, 064909 (2020).
The comparison of experimental data and theoretical predictions is crucial for our understanding of the mechanisms for interactions and particle production in hadron collisions, both at the Large Hadron Collider (LHC) and at the Relativistic Heavy-Ion Collider (RHIC). In order to help with that task, several tools were created. The Rivet (Robust Independent Validation of Experiment and Theory) framework is used as a generator-independent system for event generator validation and tuning. It provides a large set of experimental analysis algorithms (called plugins) going along with the published data. It uses the HepMC package as a common interface for events produced with different Monte Carlo generators, as well as YODA (Yet more Objects for Data Analysis) for histogramming. On top of that, the MCPLOTS framework has been and is still developed in order to automatize the creation of comparison plots and to make them accessible to everyone in the form of an online repository. These tools not only help with a comparison of different generators and experimental data but also with the preservation of the MC analysis algorithms used.
Analysis algorithm preservation offers many benefits for physicists, as well as for particle physics experiments. Preservation is essential for many reasons, such as to ensure post-publication reproducibility of the results. The heavy-ion community at large, including the ALICE Collaboration and the heavy-ion community at RHIC together with Rivet authors, is actively working on the preservation of the analyses containing some specific heavy-ion functionalities, such as centrality calibration. In this contribution, we will present the status of the developed tools and some of the open points and challenges still to be faced.
The ALICE experiment at the LHC is designed to study the hot and dense medium produced in ultra-relativistic heavy-ion collisions. Light-flavour hadrons, such as pions, kaons, protons, strange hadrons, resonances and (hyper)nuclei are optimal probes to characterise the bulk properties of the medium. This is achieved by studying particle hadro-chemistry, with a focus on strangeness production, and investigating a variety of effects, such as the impact of collective flow on the baryon-to-meson ratios, the re-scattering and regeneration in the hadronic gas, which distort hadron spectra and modify resonance yields, and the coalescent production of (hyper)nuclei. By changing the collision systems from elementary hadronic interactions to heavy-ion collisions and the collision energy, one can explore the properties of hot matter in detail. In this talk, we discuss recent ALICE results on light-flavour hadron production across different collision systems from LHC Run 2. The results are compared to lower energy measurements and to model predictions in a wide range of system sizes and collision energies.
The study of hadronic jet substructure has become a burning topic in recent years, bringing to a high request for designing precise observable to understand it. A novel observable, called the "Jet Colour Ring", aims at constructing a colour tagger, able to discriminate the decay of a colour-singlet into two jets from a two-jet background in a different colour configuration. The Jet Colour Ring performances were assessed in simulation, by applying it to the case of the production of a boosted Higgs boson decaying in two b-quarks and an associate electroweak boson. Notable discriminator powers when comparing the performances with other observables were observed, opening a wide scenario for further studies.
An important observable for studying partonic energy loss in high energy nucleus-nucleus collisions is the jet fragmentation function. Detailed investigation of low momentum (10-60 GeV) jet fragmentation functions may complement previous studies by providing more information on energy loss. The main difficulty in studying low momentum jets in heavy ion collisions is the presence of a significant uncorrelated background of low momentum hadrons from soft processes. One way to deal with this background is to use the jet-hadron azimuthal correlation to fit and subtract the soft, flow correlated background information from the jet. This technique allows one to measure the near side yield in the correlation function after background subtraction for a large number of events binned in jet transverse momentum and hadron transverse momentum. From these yields binned in transverse momentum, one can then construct a fragmentation function. We discuss the specifics of this proposed method of measuring the fragmentation function including corrections for detector effects. We present the results of a Monte Carlo study using Pythia and a custom made Heavy Ion Background Generator (along with mocked up detector effects) that demonstrate the feasibility of this method.
Keynote talk, covering state-of-the-art lattice computations and impacts on g-2 and flavour-universality anomalies.
Recently, jet measurements in DIS events close to Born kinematics have been proposed as a new probe to study transverse-momentum-dependent (TMD) PDFs, TMD fragmentation functions, and TMD evolution. We report measurements of lepton-jet momentum imbalance and hadron-in-jet correlations in high-$Q^2$ DIS events collected with the H1 detector at HERA. The jets are reconstructed with the kT algorithm in the laboratory frame. These are two examples of a new type of TMD studies in DIS, which will serve as pathfinder for the Electron-Ion Collider program.
A first measurement of the 1-jettiness event shape observable in neutral-current deep-inelastic electron-proton scattering is presented. The 1-jettiness observable 𝜏1𝑏 is defined such that it is equivalent to the thrust observable in the Breit frame, following momentum conservation. The data were taken with the H1 detector at the HERA ep collider at a center-of-mass energy of 319 GeV in the years 2003 to 2007 and correspond to an integrated luminosity of about 351pb$^{−1}$. The triple-differential cross sections are presented as a function of the 1-jettiness $\tau_{1𝑏}$, the event virtuality $Q^2$ and the Bjorken-variable $x_{Bj}$ in the kinematic region $Q^2>150$ GeV$^2$. The data have high sensitivity to the parton distribution functions of the proton, the strong coupling constant and to resummation and hadronisation effects. The data are compared to selected predictions.
We present our recent NNLO calculation of t-channel single-top-quark production and decay that resolves a disagreement between two previous calculations whose size at the inclusive level was comparable to the NNLO correction itself, and was even larger differentially. Moving beyond those comparisons, we have included b-quark tagging to allow for comparison with experiment, and added the ability to use double deep inelastic scattering (DDIS) scales ($\mu^2=Q^2$ for the light-quark line and $\mu^2=Q^2+m_t^2$ for the heavy-quark line) that allow for direct testing of parton distribution function (PDF) stability. All code will be publicly available in MCFM.
We demonstrate that several characteristic fiducial and differential standard model observables, and observables sensitive to new physics, are stable between NLO and NNLO, but point out there is a sizable difference in the prediction of some exclusive t+n-jet cross sections. Finally, we use this calculation to present preliminary results which indicate that some commonly used PDF sets are in significant disagreement, both with each other and with themselves between perturbative orders when evaluated at Tevatron energies.
We apply the formalism developed earlier [1, 2] for studying transverse momentum dependent parton distribution functions (TMDs) at small Bjorken $x$ to construct the small-$x$ asymptotics of the quark Sivers function. First, we explicitly construct the complete fundamental “polarized Wilson line” operator to sub-sub-eikonal order. We then express the quark Sivers function in terms of dipole
scattering amplitudes containing various components of the “polarized Wilson line” and show that the dominant term which contributes to the quark Sivers function at small-$x$ is the spin-dependent odderon, confirming the recent results of Dong, Zheng and Zhou [3]. Our conclusion is also similar to the case of the gluon Sivers function derived by Boer, Eschevarria, Mulders and Zhou [4] (see also [5]). We thus obtain that $f_{1T}^{\perp q} (x, k_T^2) ∼ 1/x$ at small-$x$.
[1] Y. V. Kovchegov and M. D. Sievert, Phys. Rev. D99, 054032 (2019), arXiv:1808.09010 [hep-ph].
[2] Y. V. Kovchegov and M. D. Sievert, Phys. Rev. D99, 054033 (2019), arXiv:1808.10354 [hep-ph].
[3] H. Dong, D.-X. Zheng, and J. Zhou, Phys. Lett. B 788, 401 (2019), arXiv:1805.09479 [hep-ph].
[4] D. Boer, M. G. Echevarria, P. Mulders, and J. Zhou, Phys. Rev. Lett. 116, 122001 (2016), arXiv:1511.03485 [hep-ph].
[5] L. Szymanowski and J. Zhou, Phys. Lett. B760, 249 (2016), arXiv:1604.03207 [hep-ph].
In past many studies are done on cosmic ray which are said to be messengers of universe but no one yet think to study the effects when there is a meteor showers. It opens a new window to study more about the universe or allows us to see the universe in a different way. Most of stratosphere conditions can be created in laboratories like Temperature, Pressure, humidity and even some radiations can be generated. The reason why one should opt for HAB for this experiment is cosmic rays cannot be generated and they are highly detected in high altitude in primary form rather than decayed form(secondary form) in ground observatories. Meteor shower is visible through naked eye but the effect on cosmic ray will be seen high altitude compared to ground. Detection of Cosmic ray- Particle detector can be used for detecting cosmic rays which consists of Scintillator and photomultipliers tube or sensor. Scintillator has a property scintillation- when a charged particle enters the detector, it absorbs that energy and leads to emission of light. photo tube or photomultiplier is used to multiply the light and allows us to see in digital detector. Studying the most possible effected region- Meteor showers takes place at 100 km from ground where as our balloon can reach up to the 35km, The effect may not be in 35km or less in that region of detection. we can use camera to collect the photons and can be given to cosmic detector. Main difficult is camera most be focused on meteor showers. Using GPS module, we can know the current longitude and latitude and we already know the exact location meteor shower is expected to be visible(Northern Hemisphere). We used a track algorithm to track the meteor shower based on altitude and direction with which our latex balloon is moving. No need for servo motor because we will be taking rotational camera. Building the payload for studying meteor shower effect on cosmic ray using high altitude balloon with improvised detection is selected to be launched on 12-13 August 2021 in TIRF Hyderabad.
Collective phenomena in heavy-ion collisions are very sensitive to initial geometry including nuclei deformation effects. Recent hydrodynamic calculations and preliminary data by the STAR Collaboration show such deformation effects can be probed by studying the correlation between event-wise average transverse momentum $[p_T]$ and harmonic flow $v_n$. In particular, due to prolate shape of the uranium nuclei, significant difference between Au+Au and U+U collisions is expected for these observables. This talk presents the systematic study of nuclear deformation on Pearson correlation coefficient $\rho(v_n,[p_T])$ from Au+Au at $\sqrt{s_{NN}}$ = 200 GeV and U+U at $\sqrt{s_{NN}}$ = 193 GeV collisions using a Multi-Phase Transport model (AMPT). A quantitative description of this new phenomenon can be achieved to help constrain the quadrupole deformation of the colliding species. The contamination from short-range correlation are also suppressed using the subevent cumulant method by calculating the azimuthal correlation between two or more longitudinal pseudorapidity ranges.
The everyday practice of physicists is to a large extent determined by the scientific problems they are confronted with. The conceptual analysis of scientific problems and how they change, therefore, may allow for a fine-grained investigation of the development of a scientific discipline. In this talk I discuss what constitutes a scientific problem, what its elements are and how they change. I will illustrate the advantages of a more problem-focused approach in understanding the development of modern particle physics and provide a perspective that may shed some light in the assessment of open problems and whether they constitute “genuine” problems.
Measurements of two- and multi-particle angular correlations in DIS and photoproduction ep collisions at $\sqrt{s}=319$ GeV are presented as a function of charged particle multiplicity. The data were collected using the H1 detector at HERA. Since no long-range ridge structure is observed in the correlation functions over the full multiplicity range, upper limits of ridge yield are provided as functions of particle multiplicity. The second-order ($V_{2\Delta}$) and third-order ($V_{3\Delta}$) azimuthal anisotropy Fourier harmonics of charged particles are extracted from long-range two-particle correlations as functions of particle multiplicity. The $C_2${4} signals are also extracted from four-particle correlations for the first time in ep collisions, which are positive or consistent with 0. These observations do not indicate the kind of collective behavior observed at the RHIC and LHC in high-multiplicity hadronic collisions.
H1prelim-20-033
The ALICE experiment studies the physics of strongly interacting matter, focusing on the properties of the Quark-Gluon Plasma (QGP). The relative production of strange hadrons with respect to non-strange hadrons in heavy-ion collisions was historically considered as one of the signatures of QGP formation. Recent results in proton-proton (pp) and proton-lead (p-Pb) collisions have revealed an increasing trend in the yield ratio of strange hadrons to pions with the charged particle multiplicity in the event, smoothly connecting data from different collision systems and energies.
In this talk, new studies will be presented with the aim of better understanding the strangeness enhancement phenomenon in small collision systems. In the first study the very forward energy transported by beam remnants and detected by the Zero Degree Calorimeters (ZDC) is used to classify events. In particular, strangeness production is studied exploiting the concept of the effective energy available for particle production in the event, which is estimated by an anti-correlation with the energy deposited in the calorimeters. The contribution of the effective energy and of the particle multiplicity on strangeness production is studied using a multi-differential approach in order to disentangle initial and final state effects. In the second study the origin of strangeness enhancement with multiplicity in pp has been further investigated by separating the contribution of soft and hard processes, such as jets, to strange hadron production. Techniques involving full-jet reconstruction or two-particle correlations have been exploited.
The results indicate that strangeness production emerges from the growth of the underlying event, being disconnected from initial state properties, and suggest that soft (out-of-jets) processes are the dominant contribution to strange hadron production.
Multi-particle correlations have been compelling tools to probe the properties of the Quark-Gluon Plasma (QGP) created in the ultra-relativistic heavy-ion collisions and the search for the QGP in small collision systems at the LHC. However, only very few of them are available and studied in theoretical calculations and experimental measurements, while the rest are generally very interesting, but their direct implementation was not feasible.
In this talk, I will present the newly developed generic recursive algorithm for multi-particle correlation, enabling the calculation of arbitrary order single and mixed harmonic multi-particle cumulants. Among them, the new 10-, 12-, 14-, and 16-particle cumulants of a single harmonic and the corresponding $v_n$ coefficients, can be studied for the first time. With the same algorithm, the correlations between various flow coefficients $v_{k}$, $v_{l}$ and $v_{n}$ in their different moments, will be studied based on mixed harmonic cumulants. Such a new correlation shed additional insight into correlations and fluctuations of the eccentricity coefficients in the initial state and the non-linear hydrodynamic response of the deconfined matter. Furthermore, I will show the most recent development of novel correlations between mean transverse momentum and anisotropic flow coefficients $\rho(\left< p_{\rm T} \right>, v_{n}^2)$ and also the higher-order $\rho(\left< p_{\rm T} \right>, v_{n}^2, v_{m}^{2})$ with both between experimental data, hydrodynamic and transport model calculations in Pb--Pb and Xe--Xe collisions at the LHC. This comparison could significantly improve the understanding of the initial conditions (including the nucleon structure) and also the dynamic properties of the QGP.
Polarization of Lambda hyperons, produced in relativistic heavy-ion collisions, has been discovered in 2017 by STAR experiment in the Beam-Energy Scan program at RHIC. The trends in the global Lambda polarization are in good agreement with hydrodynamic models. However, the transverse momentum dependence of polarization components in the out-of-plane direction and beam direction does not agree with the models, which constitutes a puzzle.
In this talk we present practical calculations of lambda polarization components in the out-of-plane and and beam directions, in heavy-ion collisions at $\sqrt{s_{\rm NN}} = 200$ GeV, in a 3+1 dimensional viscous hydrodynamic model vHLLE. We show that the inclusion of a recently found additional term of the spin polarization vector at local equilibrium which is linear in the symmetrized gradients of the velocity field, and the assumption of hadron production at constant temperature restore the quantitative agreement between hydrodynamic model predictions and local polarization measurements in relativistic heavy ion collisions at $\sqrt{s_{\rm NN}} = 200$ GeV.
Local density fluctuation near the QCD critical point has been suggested to exhibit a power-law behavior which can be probed by an intermittency analysis on scaled factorial moment (SFM) in relativistic heavy-ion collisions.
In this talk, I will firstly review recent heavy-ion experimental results on the intermittency measurement from STAR, NA49 and NA61 collaborations. These results are compared with several theoretical and phenomenological model predictions[1-3]. The collision energy and centrality dependence of the second-order SFMs are systematically investigated in Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV within the UrQMD model. We estimate the non-critical background in the measurement of intermittency and suggest a cumulative variable method to effectively remove the contributions from background. We further study the effect of particle detection efficiency by implementing UrQMD events in the RHIC/STAR experimental tracking efficiencies. A cell-by-cell method is proposed for experimental application of efficiency corrections on SFM. This work can provide a guidance of background subtraction and efficiency correction for experimental measurement of intermittency in the search of QCD critical point in heavy-ion collisions.
[1]Jin Wu, Yufu Lin, Yuanfang Wu and Zhiming Li, Phys. Lett. B 801, 135186 (2020).
[2]Pengcheng Li, et al., Phys. Lett. B 818, 136393 (2021).
[3]Jin Wu, Yufu Lin, Zhiming Li, Xiaofeng Luo, and Yuanfang Wu, arXiv: 2104.11524 (2021).
In the relativistic heavy-ion collisions the mean transverse momentum ($[p_{T}]$) and anisotropic flow ($v_n$, n=2,3) have been found to be tightly correlated with the size and initial geometry eccentricity of the produced fireball, respectively. It provides a novel tool to image the deformation of the atomic nuclei at extremely short time scale ($<10^{-24}$s).
In this talk, we present measurements of correlations between $v_n$ and $[p_T]$ by using the Pearson correlation coefficient ($\rho(v_{n}\{2\}^2,[p_{T}])$) as a function of multiplicity in Au+Au and U+U collisions at top RHIC energy. Unlike in Au+Au collisions, a sign-change behavior has been found for $\rho(v_{2}\{2\}^2,[p_{T}])$ in central U+U collisions due to nuclei deformations. While $\rho(v_{3}\{2\}^2,[p_{T}])$ has been found to be similar between two collision systems. Comparing with several model calculations in the ultra-central regions, such measurements will help us to constrain the quadrupole deformation parameter ($\beta_2$) of the atomic nuclei.
In the RHIC Beam Energy Scan program, gold nuclei are collided with different collision energies in the range from few to 62.4 GeV. The goals of the program are to explore the onset of QGP creation, locate the critical point of QCD and study dense baryon matter.
In this talk, we report on the first application of 3D Monte Carlo Glauber (GLISSANDO2) and TrENTO p=0 initial states for 3D event-by-event viscous fluid dynamic (vHLLE) + cascade modelling of Au+Au collisions at $\sqrt{s_{\rm NN}}=27$ and 62.4 GeV, which is the upper region of RHIC BES energies. The initial states are extended into both the longitudinal direction and for finite baryon density using simple ansätze. The full energy and baryon charge counting in the initial states is implemented. We show the reproduction of basic hadronic observables - pseudorapidity distributions of charged hadrons and net protons, transverse momentum spectra and elliptic flow, at both collision energies and with both initial states. We compare it to the existing results obtained with UrQMD initial state.
Furthermore, we show the results for rapidity decorrelation of elliptic flow $r_2$ at $\sqrt{s_{\rm NN}}=27$ and 200 GeV from the same setup of hydrodynamic calculations with the 3D Monte Carlo Glauber and UrQMD initial states. We discuss the features of the initial states responsible for the magnitude of the observed flow decorrelation, and the effect of the final-state hadronic cascade.
Publication reference: Phys. Rev. C 103, 034902 (2021)
Droplets of quark-gluon plasma produced in heavy-ion collisions rapidly evolve expanding and cooling. During considerable part of this dynamics the system can be described within relativistic hydrodynamics. Recently, there were some attempts to include effects of the medium motion to the jet energy loss and jet modification calculations in a variety of models. Here we will present the first principle consideration of the medium motion effects on the jet broadening and soft gluon radiation within opacity expansion approach. We will show that the developed formalism can be also applied to derive the effects of in-medium fluctuations on a wide range of the jet observables at EIC.
In scattering experiments, a multitude of hadronic states was observed
already in the 50s and 60s of the last century. In order to explain
their abundance, a systematic approach was taken to search for an
underlying structure. Quantum chromodynamics was developed as a
theoretical description of these strongly interacting particles,
explaining the interactions between quarks and gluons, of which hadrons
are built. However, this cannot fully describe the observed spectrum of
states - in particular, the role of gluons and how they affect the
properties of the observed states has not been resolved. Especially the
discovery of quite a few unexpected "exotic" states in recent years has
highlighted the need for precise spectroscopic measurement to understand
the nature of the underlying interaction.
In this talk, it will be shown how we use experimental data from
large-scale experiments to perform dedicated studies of the production
and decay properties of hadrons in different processes and energy
ranges. These studies provide valuable information for the
classification and identification of the observed states.
I will describe how the discrete spectrum of eigenstates of QCD in a finite box, calculated using lattice QCD techniques, can be used to infer hadron-hadron scattering amplitudes. I will illustrate the approach with the results of several calculations of coupled-channel meson-meson scattering, commenting upon the resonant content.
Heavy quarks (charm and beauty) are produced at the initial stages of the relativistic hadronic collisions in hard scattering processes. The study of heavy-flavor production provides a stringent test to perturbative Quantum Chromo-Dynamics (pQCD) calculations in proton-proton (pp) collisions and can help in disentangling cold nuclear matter (CNM) effects in proton-lead (p--Pb) collisions. Analysis of charm production as a function of charged-particle multiplicity lets us investigate the role of multi-parton interactions (MPI) in particle production, color-reconnection (CR) mechanisms in hadronization, and the interplay between the hard and soft particle production in pp and p--Pb collisions. Heavy-flavor production measurements in high multiplicity pp and p--Pb collisions indicate possible modification of the particle spectra compared to minimum bias measurements. These results raise questions about the collective nature of the QCD matter produced in small systems, which are typically observed in Pb--Pb collisions.
In this contribution, measurements of open heavy-flavor production as a function of multiplicity, via the study of the $\mathrm{D}$-meson and heavy-flavor decay leptons using self-normalized yields in pp collisions at the center-of-mass energy of $\sqrt{s} = 13$ TeV are discussed. The self normalised yields increase stronger than linearly with increasing charged-particle multiplicity and tend to have a steeper trend with increasing $p_{\rm{T}}$. Comparisons are made with similar measurements of J$/\psi$ at $\sqrt{s} = 13$ TeV and D-mesons at $\sqrt{s} = 7$ TeV and various model predictions. The $\Lambda_{\rm{c}}^{+}/\rm{D}^{0}$ and $\rm{D^{+}_{s}/D^0}$ ratio measurements in different multiplicity intervals in pp collisions at $\sqrt{s} = 13$ TeV are also shown. Enhancement of $\Lambda_{\rm{c}}^{+}/\rm{D}^{0}$ is observed when compared to $\rm{e^+e^-}$ collisions and with increasing multiplicity, whereas no such behaviour is seen for $\rm{D^{+}_{s}/D^0}$. Finally, the nuclear modification factor calculations are shown for open charm hadrons at $\sqrt{s} = 5.02$ TeV in p--Pb collisions. Measurement of D-meson $Q_{\rm{cp}}$ and elliptic flow of heavy-flavor decay leptons in similar systems are presented. Both these measurements hint towards a possible collective behaviour of the QCD matter forming in high multiplicity p--Pb collisions.
We describe an analysis comparing the $p\bar{p}$ elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96~TeV to that in $pp$ collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeV using a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of $\sqrt{s} =$ 1.96 TeV, are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the $pp$ cross section.
The two data sets disagree at the 3.4$\sigma$ level and thus provide evidence for the $t$-channel exchange of a colorless, $C$-odd gluonic compound, also known as the odderon.
We combine these results with a TOTEM analysis of the same $C$-odd exchange based on the total cross section and the ratio of the real to imaginary parts of the forward elastic strong interaction scattering amplitude in $pp$ scattering for which the significance is between 3.4 and 4.6$\sigma$.
The combined significance is larger than 5$\sigma$ and is interpreted as the first observation of the exchange of a colorless, $C$-odd gluonic compound.
Recently, a statistically significant signal for the observation of the odderon has been published in EPJ C, that reported an Odderon signal of at least 6.26 sigma, based on a scaling analysis of the differential cross-sections of elastic pp and pbarp scattering in the TeV energy range [1]. The D0 and TOTEM collaborations reported an at least 5.2 sigma Odderon signal from a comparison of the pp and pbarp differential cross-sections in a kinematic range limited to the diffractive interference region, combined with the measurement of the pp total cross-sections and the real-to imaginary ratio rho at 13 TeV [2]. We have analyzed the similarities and the differences of these two approaches and propose here a novel gating method that allows to separate the Odderon signal from its background. This method is utilized to determine the domain of validity of the scaling behaviour of the differential cross-section at the TeV energy range, and to determine the signal range optimalized significance of the Odderon observation. We find that the optimized statistical significance for the Odderon observation on the TeV energy scale, based on published differential cross-section data of elastic pp and pbarp scattering, is at least 6.33 sigma, improving on both the D0-TOTEM estimate and our earlier results of 6.26 sigma. Outside this optimal Odderon signal window, the background of the Odderon signal is found to agree between pp and pbarp within 1.7 sigma.
[1] T. Csörgő, T. Novák, R. Pasechnik, A. Ster and I. Szanyi:
Evidence of Odderon-exchange from scaling properties of elastic scattering at TeV energies.
Eur. Phys. J. C 81, 180 (2021). https://doi.org/10.1140/epjc/s10052-021-08867-6
[2] D0 and TOTEM Collaborations, V. M. Abazov et al. :
Comparison of pp and pbarp differential elastic cross sections and observation of the exchange of a colorless C-odd gluonic compound
e-Print: 2012.03981 [hep-ex], accepted for a publication in the Physical Review Letters on June 10, 2021
We present recent BFKL phenomenological studies for several novel probes that have been proposed for the LHC and different collider environments. Since that the typical BFKL observables at the LHC are the azimuthal angle $\phi$ correlations of tagged particles in the final state, which are separated in rapidity, a specific attention has been drawn to the behaviour of the so-called azimuthal correlation.
We use a recently proposed formalism which includes both small and large x gluons of a target nucleus (or proton) to calculate the photon-parton production cross section. This allows one to investigate azimuthal angular correlations between the produced photon and parton from low to high p_t, as well as the forward-backward rapidity correlations between the them.
Two-particle transverse momentum correlator is a powerful technique for understanding the dynamics of relativistic heavy-ion collisions. Among these, the transverse momentum correlator $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ is of particular interest for its potential sensitivity to the shear viscosity per entropy density $\eta/s$ of the quark-gluon plasma formed in heavy-ion collisions~[1,2]. We used Au--Au at $\sqrt{s_{\rm NN}}$ = 200~GeV data to investigate: (i) the self-correlations associated with the definition of the collision centrality[3], (ii) the longitudinal broadening of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator, (iii) the long range azimuthal dependence of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$. We will present the centrality and event shape dependence of the longitudinal width $\sigma\left( \Delta\eta \right)$ and the azimuthal harmonics $a^{p_T}_{n}$ of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator. Our measurements are compared to similar LHC measurements as well as with calculations using the UrQMD, AMPT, and EPOS models~[4]. These comparisons are expected to reflect the efficacy of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator to differentiate among theoretical models as well as to constrain the $\eta/s$.
[1] S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97, 162302 (2006)
[2] V. Gonzalez, et al., Eur.Phys.J.C 81 (2021) 5, 465
[3] N. Magdy, et al., arXiv:2101.01555
[4] N. Magdy, et al., arXiv:2105.07912
In the past years, significant progress has happened in high-energy nuclear physics models. A more robust and quantitative picture has replaced the qualitative descriptions of heavy nuclei collisions in the earlier days, enabling us to have a clearer picture of different stages of a heavy-ion collision. These models typically have $O(10)$ free parameters that are tuned by Bayesian analysis in recent years. To better understand the free parameter values, it is essential to experimentally probe their phase space by observables, each containing independent information of the model.
In this presentation, our focus is on anisotropic flow observables. We introduce a method to extract anisotropic flow cumulant systematically. Employing a Monte Carlo simulation tuned by Bayesian analysis results, we predict the value of some low-order flow harmonic cumulants with significant signals that have not been reported by the LHC so far. Moreover, we introduce a new method to extract the linear and nonlinear hydrodynamic response coefficients based on our multiharmonic cumulant study. Besides, this systematic study enables us to propose a genuine three-particle correlation function for the first time. This observable is a summation of all third-order flow harmonic cumulants of all harmonics. The large-order flow cumulant ($v_n\{2k\}$ with large $k$) contains a unique piece of information about the underlying flow distribution. In particular, we discuss the relation between the nonvanishing Lee-Yang zero phase and large-order flow cumulant ratios at ultra-central, ultra-peripheral, large, and small collision systems.
In the past years, significant progress has happened in high-energy nuclear physics models. A more robust and quantitative picture has replaced the qualitative descriptions of heavy nuclei collisions in the earlier days, enabling us to have a clearer picture of different stages of a heavy-ion collision. These models typically have $O(10)$ free parameters that are tuned by Bayesian analysis in recent years. To better understand the free parameter values, it is essential to experimentally probe their phase space by observables, each containing independent information of the model.
In this presentation, our focus is on anisotropic flow observables. We introduce a method to extract anisotropic flow cumulant systematically. Employing a Monte Carlo simulation tuned by Bayesian analysis results, we predict the value of some low-order flow harmonic cumulants with significant signals that have not been reported by the LHC so far. Moreover, we introduce a new method to extract the linear and nonlinear hydrodynamic response coefficients based on our multiharmonic cumulant study. Besides, this systematic study enables us to propose a genuine three-particle correlation function for the first time. This observable is a summation of all third-order flow harmonic cumulants of all harmonics. The large-order flow cumulant ($v_n\{2k\}$ with large $k$) contains a unique piece of information about the underlying flow distribution. In particular, we discuss the relation between the nonvanishing Lee-Yang zero phase and large-order flow cumulant ratios at ultra-central, ultra-peripheral, large, and small collision systems.
Two-particle transverse momentum correlator is a powerful technique for understanding the dynamics of relativistic heavy-ion collisions. Among these, the transverse momentum correlator $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ is of particular interest for its potential sensitivity to the shear viscosity per entropy density $\eta/s$ of the quark-gluon plasma formed in heavy-ion collisions~[1,2]. We used Au--Au at $\sqrt{s_{\rm NN}}$ = 200~GeV data to investigate: (i) the self-correlations associated with the definition of the collision centrality[3], (ii) the longitudinal broadening of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator, (iii) the long range azimuthal dependence of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$. We will present the centrality and event shape dependence of the longitudinal width $\sigma\left( \Delta\eta \right)$ and the azimuthal harmonics $a^{p_T}_{n}$ of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator. Our measurements are compared to similar LHC measurements as well as with calculations using the UrQMD, AMPT, and EPOS models~[4]. These comparisons are expected to reflect the efficacy of the $G_{2}\left(\Delta\eta,\Delta\varphi\right)$ correlator to differentiate among theoretical models as well as to constrain the $\eta/s$.
[1] S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97, 162302 (2006)
[2] V. Gonzalez, et al., Eur.Phys.J.C 81 (2021) 5, 465
[3] N. Magdy, et al., arXiv:2101.01555
[4] N. Magdy, et al., arXiv:2105.07912
The light-front holography or light-front AdS/QCD is defined as a connection between light-front QCD and the description of hadronic modes on AdS spacetime. This relation, inspired in the AdS/CFT correspondence, has shown improvements in analytic solutions in the hadron physics regime.
We are motivated by the light-front AdS/QCD prediction on a general form of two particle bound state wave function inside nucleons. Diquark degrees-of-freedom within the framework of a quark model have been suggested also in the baryon structure in lattice-QCD as well as in phenomenological resources to study observed data.
This fact has motivated studies of nucleon models considering diquarks in their valence structure, the so called quark-diquark nucleon models. One of these studies has been shown light-front wave functions QCD matched with light-front AdS/QCD predictions. From such result, followed a model that contemplates the scale evolution of the Parton Distribution Functions (PDFs) for a quark-diquark nucleon model using scale dependent parameters following the DGLAP evolution.
Based on these results, we have performed a calculation of the PDF parameters constructed on the so called AdS/QCD quark-diquark nucleon model from the available data from NNPDF collaboration for u and d quarks, in order to get the unpolarized PDFs for the scalar and axial-vector diquarks in protons and neutrons. The PDFs obtained are expected to be used in nucleon and heavy-ion collision simulations to study the role of valence-diquark hard-processes on hadron production.
In the RHIC Beam Energy Scan program, gold nuclei are collided with different collision energies in the range from few to 62.4 GeV. The goals of the program are to explore the onset of QGP creation, locate the critical point of QCD and study dense baryon matter.
In this talk, we report on the first application of 3D Monte Carlo Glauber (GLISSANDO2) and TrENTO p=0 initial states for 3D event-by-event viscous fluid dynamic (vHLLE) + cascade modelling of Au+Au collisions at $\sqrt{s_{\rm NN}}=27$ and 62.4 GeV, which is the upper region of RHIC BES energies. The initial states are extended into both the longitudinal direction and for finite baryon density using simple ansätze. The full energy and baryon charge counting in the initial states is implemented. We show the reproduction of basic hadronic observables - pseudorapidity distributions of charged hadrons and net protons, transverse momentum spectra and elliptic flow, at both collision energies and with both initial states. We compare it to the existing results obtained with UrQMD initial state.
Furthermore, we show the results for rapidity decorrelation of elliptic flow $r_2$ at $\sqrt{s_{\rm NN}}=27$ and 200 GeV from the same setup of hydrodynamic calculations with the 3D Monte Carlo Glauber and UrQMD initial states. We discuss the features of the initial states responsible for the magnitude of the observed flow decorrelation, and the effect of the final-state hadronic cascade.
Publication reference: Phys. Rev. C 103, 034902 (2021)
An important observable for studying partonic energy loss in high energy nucleus-nucleus collisions is the jet fragmentation function. Detailed investigation of low momentum (10-60 GeV) jet fragmentation functions may complement previous studies by providing more information on energy loss. The main difficulty in studying low momentum jets in heavy ion collisions is the presence of a significant uncorrelated background of low momentum hadrons from soft processes. One way to deal with this background is to use the jet-hadron azimuthal correlation to fit and subtract the soft, flow correlated background information from the jet. This technique allows one to measure the near side yield in the correlation function after background subtraction for a large number of events binned in jet transverse momentum and hadron transverse momentum. From these yields binned in transverse momentum, one can then construct a fragmentation function. We discuss the specifics of this proposed method of measuring the fragmentation function including corrections for detector effects. We present the results of a Monte Carlo study using Pythia and a custom made Heavy Ion Background Generator (along with mocked up detector effects) that demonstrate the feasibility of this method.
In past many studies are done on cosmic ray which are said to be messengers of universe but no one yet think to study the effects when there is a meteor showers. It opens a new window to study more about the universe or allows us to see the universe in a different way. Most of stratosphere conditions can be created in laboratories like Temperature, Pressure, humidity and even some radiations can be generated. The reason why one should opt for HAB for this experiment is cosmic rays cannot be generated and they are highly detected in high altitude in primary form rather than decayed form(secondary form) in ground observatories. Meteor shower is visible through naked eye but the effect on cosmic ray will be seen high altitude compared to ground. Detection of Cosmic ray- Particle detector can be used for detecting cosmic rays which consists of Scintillator and photomultipliers tube or sensor. Scintillator has a property scintillation- when a charged particle enters the detector, it absorbs that energy and leads to emission of light. photo tube or photomultiplier is used to multiply the light and allows us to see in digital detector. Studying the most possible effected region- Meteor showers takes place at 100 km from ground where as our balloon can reach up to the 35km, The effect may not be in 35km or less in that region of detection. we can use camera to collect the photons and can be given to cosmic detector. Main difficult is camera most be focused on meteor showers. Using GPS module, we can know the current longitude and latitude and we already know the exact location meteor shower is expected to be visible(Northern Hemisphere). We used a track algorithm to track the meteor shower based on altitude and direction with which our latex balloon is moving. No need for servo motor because we will be taking rotational camera. Building the payload for studying meteor shower effect on cosmic ray using high altitude balloon with improvised detection is selected to be launched on 12-13 August 2021 in TIRF Hyderabad.
Medium-induced gluon radiation is known to be an important tool to extract the properties of the QGP created in heavy-ion collisions. I will use a recent approach to evaluate the full in-medium gluon emission spectrum, including the resummation of all multiple scatterings, to analyze the validity of the usually employed analytical approximations. More specifically, by using this all-order result I will determine the kinematic regions in which the effects of multiple scatterings are essential and where, in contrast, a single hard scattering is enough to describe the in-medium emission process. Furthermore, I will compute the effects due to the inclusion of a time delay in the production of the medium has on the emission spectrum.
Multiparticle correlations measurements in even the smallest collision systems are consistent with predictions from viscous relativistic hydrodynamics calculations. However, these hydrodynamics calculations use a continuum extrapolated---i.e. infinite volume---equation of state. For the modest temperature probed in these small collisions, the controlling dimensionless product of the temperature and system size T*L ~ 400 MeV * 2 fm / 197 MeV fm ~ 4 is not particularly large. One should therefore investigate the small system size corrections to the equilibrium QCD equation of state used in modern viscous hydrodynamics simulations.
We present first results on just such finite system size corrections to the equation of state, trace anomaly, and speed of sound for two model systems: 1) free, massless scalar theory and 2) quenched QCD with periodic boundary conditions (PBC). We further present work-in-progress results for quenched QCD with Dirichlet boundary conditions.
We show that free, massless scalar fields, which are maximally sensitive to the finite size box, deviate enormously from their infinite volume conformal limit. Quenched QCD with PBC show corrections of ~20% for the trace anomaly near the phase transition. These corrections are more modest, but will have a meaningful, quantitative impact on the extracted bulk and shear viscosities in these small systems.
This presentation is based on
Mogliacci et al., Phys.Rev.D 102 (2020) 11, 116017 [arXiv:1807.07871]
Kitazawa et al., Phys.Rev.D 99 (2019) 9, 094507 [arXiv:1904.00241]
Horowitz and Rothkopf, in progress
The study of hadronic jet substructure has become a burning topic in recent years, bringing to a high request for designing precise observable to understand it. A novel observable, called the "Jet Colour Ring", aims at constructing a colour tagger, able to discriminate the decay of a colour-singlet into two jets from a two-jet background in a different colour configuration. The Jet Colour Ring performances were assessed in simulation, by applying it to the case of the production of a boosted Higgs boson decaying in two b-quarks and an associate electroweak boson. Notable discriminator powers when comparing the performances with other observables were observed, opening a wide scenario for further studies.
Charged pions, which obviously carry no baryon number, possess, however, a nontrivial baryonic structure, stemming from the isospin breaking with the up and down quark mass splitting and the EM effects. We obtain estimates for the corresponding pion baryonic (vector isoscalar) form factor in two ways: from simple constituent quark models on one hand, and from vector meson dominance model fits to the e+e- → π+π- data on the other hand. All our estimates yield a positive baryon mean square radius of pi+, in the range (0.03 − 0.04 fm)^2. Hence, a picture emerges where the outer spatial region of pi+ has a net baryon density (u excess), and the inner region a net antibaryon density (d-bar excess), both compensating each other such that the total baryon number is zero. For π− the effect is equal and opposite. We also discuss the challenging lattice QCD prospects of measuring this fundamental property of the pion.
Based on 2103.09131 [hep-ph]
Semi-visible jets arise in strongly interacting dark sectors, where parton evolution includes dark sector emissions, resulting in jets overlapping with missing transverse momentum. The implementation of semi-visible jets is done using the Pythia Hidden valley module to duplicate the dark sector showering. In this work, several jet substructure observables have been examined to compare semi-visible jets and light quark/gluon jets. These comparisons were performed using different dark hadron fraction in the semi-visible jets (signal). The extreme scenarios where signal consists either of entirely dark hadrons or visible hadrons offers a chance to understand the effect of the specific dark shower model employed in these comparisons. Looking at the different dark hadron fractions additionally, allows to check whether the substructure is created by the interspersing of visible hadrons with dark hadrons, or from certain model dependencies.
Droplets of quark-gluon plasma produced in heavy-ion collisions rapidly evolve expanding and cooling. During considerable part of this dynamics the system can be described within relativistic hydrodynamics. Recently, there were some attempts to include effects of the medium motion to the jet energy loss and jet modification calculations in a variety of models. Here we will present the first principle consideration of the medium motion effects on the jet broadening and soft gluon radiation within opacity expansion approach. We will show that the developed formalism can be also applied to derive the effects of in-medium fluctuations on a wide range of the jet observables at EIC.
Collective phenomena in heavy-ion collisions are very sensitive to initial geometry including nuclei deformation effects. Recent hydrodynamic calculations and preliminary data by the STAR Collaboration show such deformation effects can be probed by studying the correlation between event-wise average transverse momentum $[p_T]$ and harmonic flow $v_n$. In particular, due to prolate shape of the uranium nuclei, significant difference between Au+Au and U+U collisions is expected for these observables. This talk presents the systematic study of nuclear deformation on Pearson correlation coefficient $\rho(v_n,[p_T])$ from Au+Au at $\sqrt{s_{NN}}$ = 200 GeV and U+U at $\sqrt{s_{NN}}$ = 193 GeV collisions using a Multi-Phase Transport model (AMPT). A quantitative description of this new phenomenon can be achieved to help constrain the quadrupole deformation of the colliding species. The contamination from short-range correlation are also suppressed using the subevent cumulant method by calculating the azimuthal correlation between two or more longitudinal pseudorapidity ranges.
There have been recent updates to the three global PDF fits (CT, MSHT and NNPDF), all using significant amounts of data from the LHC, in addition to the non-LHC data sets that formed the core of previous iterations. Given the impact of the LHC data on the global PDF fits, and the impact that the new PDFs will have on physics comparisons at the LHC, it is crucial to perform a benchmarking among the PDFs and the predictions using these PDFs, similar in spirit to what was carried out for PDF4LHC15, widely used for LHC physics. The end result of this exercise will be a PDF4LHC21 set of PDFs, formed from the combination of the three global PDF sets. This talk will detail the benchmarking that has been performed, the similarities and differences observed, the future direction of this work and the potential impact of the PDF4LHC21 PDFs on precision physics at the LHC.
Nucleons are one of the most fundamental building blocks of ordinary matter, yet their internal structure and dynamics are still not fully understood. Electromagnetic form factors allow to investigate fundamental properties of the nucleon. The BESIII collaboration has studied the time-like form factors of the proton using the energy scan and the ISR technique. The |GE/GM| ratio is obtained with a precision comparable to the investigations of the space-like EMFF in electron proton scattering. The effective form factor of the neutron is measured with highest precision using the scan method. For both nucleons, an intriguing periodic behavior of effective form factors lineshape is observed. In this presentation the latest results on nucleon form factors at BESIII are discussed.
We present a Monte Carlo based analysis of the combined world data on polarized lepton-nucleon deep-inelastic scattering at small Bjorken $x$ within the polarized quark dipole formalism. We show for the first time that double-spin asymmetries at $x<0.1$ can be successfully described using only small-$x$ evolution derived from first-principles QCD, allowing predictions to be made for the $g_1$ structure function at much smaller $x$. Anticipating future data from the Electron-Ion Collider, we assess the impact of electromagnetic and parity-violating polarization asymmetries on $g_1$ and demonstrate an extraction of the individual flavor helicity PDFs at small $x$.
We present a complete set of transverse momentum dependent (TMD) parton densities with the Parton Branching (PB) method. TMDs extracted at LO and NLO from HERA DIS data with different number of active flavours. We also present the first TMD density of the photon, covering a wide range in $x$, $k_t$ and $\mu$. The advantage of PB method is that extracted densities automatically contain soft gluon resummation, and it is shown to coincide with the Collins-Soper-Sterman approach through next-to-leading-logarithmic order.
One of the main goals of RHIC beam energy scan (BES) program is to search for the signatures of QCD critical point in heavy-ion collisions. It is predicted that the local density fluctuations near the critical point exhibit power-law scaling, which can be probed with an intermittency analysis of the scaled factorial moments, $F_{q}(M)$, for charged particles. The power-law behavior of $q^{th}$ order scaled factorial moments can be expressed as: $F_{q}(M)\sim F_{2}(M)^{\beta_{q}}$, where $M$ is the number of equally sized cells in one dimension of momentum space, and $\beta_{q}$ is the intermittency exponent. The scaling exponent, $\nu$, related to the critical component can be derived from the equation: $\beta_{q}\sim (q-1)^{\nu}$. The energy dependence of $\nu$ could be used to search for the signature of the QCD critical point. Similar measurements have been carried out by NA49 and NA61 experiments in heavy-ion collisions with different system sizes.
In this talk, we will present the scaled factorial moments ($F_{q}(M)$, up to sixth order) of charged particles in Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 - 200 GeV measured by STAR experiment in the first phase of RHIC BES. Then, we will show the energy and centrality dependence of the extracted $\nu$ values. The physical implications of these results will be discussed.
We investigate the validity of the limiting-fragmentation hypothesis and its centrality dependence in relativistic heavy-ion collisions at energies reached at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC).
A phenomenological analysis of Au-Au and Pb-Pb collisions within a three-source relativistic diffusion model (RDM) is performed at $\sqrt{s_{NN}}=19.6, 62.4, 130, 200, 2760$ and $5023$ GeV using four centrality cuts at each energy. Linear and nonlinear expressions for the rapidity drift function are tested and their physical relevance is discussed. Our results are compatible with the limiting-fragmentation conjecture for the investigated centralities in the full energy range. However, data in the fragmentation region are not yet available at LHC energies. The number of particles in the fragmentation and fireball sources are found to depend on $\sqrt{s_{NN}}$ logarithmically and cubic-logarithmically, respectively.
[1] B. Kellers, G. Wolschin, Prog. Theor. Exp. Phys. 2019, 053D03 (2019) and Eur. Phys. J. A 57, 47 (2021).
[2] B. Alver et al. (PHOBOS Collaboration), Phys. Rev. C 83, 024913 (2011).
[3] E. Abbas et al. (ALICE Collaboration), Phys. Lett. B 726, 610 (2013).
[4] J. Adam et al. (ALICE Collaboration), Phys. Lett. B 772, 567 (2017).
[5] G. Wolschin, Universe 6, 61 (2020).
This talk gives an overview of the latest hard process measurements in heavy ion collision systems with the ATLAS detector at the LHC, utilizing the high statistics 5.02 TeV Pb+Pb data collected in 2018. These include multiple measurements of jet production and structure, which probe the dynamics of the hot, dense Quark-Gluon Plasma formed in relativistic nucleus-nucleus collisions; measurements of electroweak boson production to constrain the modifications of nuclear parton densities and test the Glauber model and binary scaling picture of heavy ion collisions; and measurements of quarkonia and heavy flavor production to probe the QGP medium properties. A particular focus of the measurements is the systematic comparison of fully unfolded data to state of the art theoretical models.
The physics of jet quenching, a generic denomination for the modifications of jets produced in the dense environment of an ultra-relativistic nucleus-nucleus collision, represents one of the main tools at our disposal to experimentally probe the quark-gluon plasma. In this talk, I will discuss recent theoretical breakthrough in our understanding of this physical phenomenon, within the framework of perturbative QCD. My focus will be on the main perturbative mechanisms that drive the modifications of jet observables in heavy-ion collisions, highlighting a new emergent picture for the jet evolution in dense QCD media. As an application of these developments, I will consider the particular case of jet substructure observables, and explain how these techniques can help to pin down specific aspects of the jet dynamics.
Interactions of high-$p_{\rm{T}}$ partons with quark-gluon plasma (QGP) result in jet quenching, which is manifest by the suppression of high-$p_{\rm{T}}$ jet yields and the modification of jet substructure and di-jet acoplanarity distributions. Several jet quenching phenomena can be measured precisely over a wide range of jet $p_{\rm{T}}$ using semi-inclusive distributions of charged jets recoiling from a high-$p_{\rm{T}}$ trigger hadron, which incorporate data-driven suppression of the large uncorrelated background produced in heavy-ion collisions.
In this talk we report semi-inclusive measurements of hadron-jet acoplanarity in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV and high-particle multiplicity pp collisions at $\sqrt{s} = 13$ TeV. In the Pb-Pb system, where QGP formation is established, narrowing of the acoplanarity is observed relative to a reference distribution from pp collisions. In contrast, pp events with high-particle multiplicity exhibit a broadening of the acoplanarity relative minimum bias events. In this case, however, qualitatively similar features are also seen in pp collisions generated by the PYTHIA 8, which does not include jet quenching or other QGP effects. We will discuss the current status of these analyses, and prospects to understand the origin of these striking phenomena.
Jet Substructure measurements will be presented with some emphasis on inclusive observables in various specific phase space regions or for different signal processes. Measurements dealing with jet tagging techniques, including the use of multivariate techniques, their performance comparisons and specific use cases like top tagging will also be discussed.