Impact of Medium Anisotropy on Quarkonium Dissociation and Regeneration

Quarkonium production in ultra-relativistic collisions plays a crucial role in probing the existence of hot QCD matter. This study explores quarkonia states dissociation and regeneration in the hot QCD medium while considering momentum anisotropy. The net quarkonia decay width ($\Gamma_{D}$) arises from two essential processes: collisional damping and gluonic dissociation. The quarkonia regeneration includes the transition from octet to singlet states within the anisotropic medium. Our study utilizes a medium-modified potential that incorporates anisotropy via particle distribution functions. This modified potential gives rise to collisional damping for quarkonia due to the surrounding medium, as well as the transition of quarkonia from singlet to octet states due to interactions with gluons. Furthermore, we employ the detailed balance approach to investigate the regeneration of quarkonia within this medium. Our comprehensive analysis spans various temperature settings, transverse momentum values, and anisotropic strengths. Notably, we find that, in addition to medium temperatures and heavy quark transverse momentum, anisotropy significantly influences the dissociation and regeneration of various quarkonia states.Comment: 9 pages and 4 captioned figure

J/ψJ/\psi and ψ\psi(2S) polarization in proton-proton collisions at the LHC energies using PYTHIA8

The production mechanisms of charmonium states in both hadronic and heavy-ion collisions hold great significance for investigating the hot and dense QCD matter. Studying charmonium polarization in ultra-relativistic collisions can also provide insights into the underlying production mechanisms. With this motivation, we explore the $J/\psi$ and $\psi$(2S) polarization in proton+proton collisions at $\sqrt{s}$ = 7, 8, and 13 TeV using a pQCD-inspired Monte-Carlo event generator called PYTHIA8. This work considers reconstructed quarkonia through their dimuons decay channel in the ALICE forward rapidity acceptance range of $2.5 < y_{\mu \mu} < 4$. Further, we calculate the polarization parameters $\lambda_{\theta}$, $\lambda_{\phi}$, $\lambda_{\theta \phi}$ from the polar and azimuthal angular distributions of the dimuons in helicity and Collins-Soper frames. This study presents a comprehensive measurement of the polarization parameters as a function of transverse momentum, charged-particle multiplicity, and rapidity at the LHC energies. Our findings of charmonium polarization are in qualitative agreement with the corresponding experimental data.Comment: 10 pages and 5-captioned figures. Submitted for publicatio

Impact of vorticity and viscosity on the hydrodynamic evolution of hot QCD medium

The strongly interacting transient quark-gluon plasma (QGP) medium created in ultra-relativistic collisions survive for a duration of a few fm/c. The spacetime evolution of QGP crucially depends on the equation of state (EoS), vorticity, viscosity, magnetic field, etc. In the present study, we obtain the QGP lifetime considering it as a 1+1-dimensionally (1+1) D expanding fluid by using second-order viscous hydrodynamics. We observe that the coupling of vorticity and viscosity significantly increases the lifetime of rotating QGP. Incorporating a static magnetic field along with vorticity and viscosity makes the evolution slower. However, for a non-rotating medium, the static magnetic field slightly decreases the QGP lifetime by accelerating the evolution process. We also report the rate of change of vorticity in the QGP medium, which can be helpful in studying the medium behavior in detail.Comment: 16 pages and 20 captioned figures. Submitted for publicatio

Dynamics of Hot QCD Matter -- Current Status and Developments

The discovery and characterization of hot and dense QCD matter, known as Quark Gluon Plasma (QGP), remains the most international collaborative effort and synergy between theorists and experimentalists in modern nuclear physics to date. The experimentalists around the world not only collect an unprecedented amount of data in heavy-ion collisions, at Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory (BNL) in New York, USA, and the Large Hadron Collider (LHC), at CERN in Geneva, Switzerland but also analyze these data to unravel the mystery of this new phase of matter that filled a few microseconds old universe, just after the Big Bang. In the meantime, advancements in theoretical works and computing capability extend our wisdom about the hot-dense QCD matter and its dynamics through mathematical equations. The exchange of ideas between experimentalists and theoreticians is crucial for the progress of our knowledge. The motivation of this first conference named "HOT QCD Matter 2022" is to bring the community together to have a discourse on this topic. In this article, there are 36 sections discussing various topics in the field of relativistic heavy-ion collisions and related phenomena that cover a snapshot of the current experimental observations and theoretical progress. This article begins with the theoretical overview of relativistic spin-hydrodynamics in the presence of the external magnetic field, followed by the Lattice QCD results on heavy quarks in QGP, and finally, it ends with an overview of experiment results.Comment: Compilation of the contributions (148 pages) as presented in the `Hot QCD Matter 2022 conference', held from May 12 to 14, 2022, jointly organized by IIT Goa & Goa University, Goa, Indi

Centrality and transverse momentum dependent suppression of Υ(1S)\Upsilon (1S) Υ(1S) and Υ(2S)\Upsilon (2S) Υ(2S) in p–Pb and Pb–Pb collisions at the CERN Large Hadron Collider

Abstract Deconfined QCD matter in heavy-ion collisions has been a topic of paramount interest for many years. Quarkonia suppression in heavy-ion collisions at the relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) experiments indicate the quark-gluon plasma (QGP) formation in such collisions. Recent experiments at LHC have given indications of hot matter effect in asymmetric p–Pb nuclear collisions. Here, we employ a theoretical model to investigate the bottomonium suppression in Pb–Pb at $$\sqrt{s_{NN}}=2.76$$ sNN=2.76 , 5.02 TeV, and in p–Pb at $$\sqrt{s_{NN}}=5.02$$ sNN=5.02 TeV center-of-mass energies under a QGP formation scenario. Our present formulation is based on an unified model consisting of suppression due to color screening, gluonic dissociation along with the collisional damping. Regeneration due to correlated $$Q\bar{Q}$$ QQ¯ pairs has also been taken into account in the current work. We obtain here the net bottomonium suppression in terms of survival probability under the combined effect of suppression plus regeneration in the deconfined QGP medium. We mainly concentrate here on the centrality, $$N_\text {part}$$ Npart and transverse momentum, $$p_{T}$$ pT dependence of $$\Upsilon (1S)$$ Υ(1S) and $$\Upsilon (2S)$$ Υ(2S) states suppression in Pb–Pb and p–Pb collisions at mid-rapidity. We compare our model predictions for $$\Upsilon (1S)$$ Υ(1S) and $$\Upsilon (2S)$$ Υ(2S) suppression with the corresponding experimental data obtained at the LHC energies. We find that the experimental observations on $$p_t$$ pt and $$N_\text {part}$$ Npart dependent suppression agree reasonably well with our model predictions

Characterizing nuclear modification effects in high-energy O-O collisions at energies available at the CERN Large Hadron Collider: A transport model perspective

International audienceThe present work focuses on oxygen-oxygen (O-O) collisions, which are planned at the CERN Large Hadron Collider. Oxygen, being a doubly magic number nucleus, has some very unique features. This study attempts to probe the exotic state of QCD matter in O-O collisions. Additionally, the role of different nuclear density profiles in governing the final-state dynamics in ultrarelativistic nuclear collisions is also explored. Using a multiphase transport model, we obtain the nuclear modification factor (RAA) for all charged hadrons and identified particles for O-O collisions at sNN = 7 TeV. Furthermore, we investigate the behavior of RAA as a function of transverse momentum (pT) for three centralities (most central, mid-central, and peripheral) considering both α-cluster and Woods-Saxon nuclear density profiles. We also extend this work to study the rapidity dependence of RAA for all charged hadrons. To better understand our findings of O-O collisions, the results are confronted with the available data of RAA for Pb-Pb collisions. The present study sheds light on particle production mechanisms, emphasizing factors influencing particle yield from precollision to postcollision stages in the context of O-O collisions

Consequence of strangeness enhancement at LHC on excess muon production in cosmic ray air showers

International audiencePrimary cosmic rays (PCRs) can have energies up to 1020 eV and provide the unique opportunity to study particle production dynamics at center-of-mass energies and kinematic regions inaccessible at particle accelerators. On interacting with atmospheric nuclei, they produce a multitude of particles that further interact or decay based on their energies. This produces a cascade of particles known as extensive air showers (EAS)

Energy flow in Ultra High Energy Cosmic Ray interactions as a probe of thermalization and potential solution to the Muon puzzle

International audienceIndicators that illustrate the formation of a strongly interacting thermalized matter of partons have been observed in high-multiplicity proton-proton, proton-nucleus, and nucleus-nucleus collisions at RHIC and LHC energies. Strangeness enhancement in such ultra-relativistic heavy-ion collisions is considered to be a consequence of this thermalized phase, known as quark-gluon plasma (QGP). Simultaneously, proper modeling of hadronic energy fraction in interactions of ultra-high energy cosmic rays (UHECR) has been proposed as a solution for the muon puzzle. These interactions have center-of-mass collision energies in the order of LHC or higher, indicating that the possibility of a thermalized partonic state cannot be overlooked in UHECR-air interactions. This work investigates the hadronic energy fraction and strangeness enhancement to explore QGP-like phenomena in UHECR-air interactions using various high-energy hadronic models. A thermalized system with statistical hadronization is considered through the EPOS LHC model, while PYTHIA 8, QGSJET II-04, and SYBILL 2.3d consider string fragmentation in the absence of any thermalization. We have found that EPOS LHC gives a better description of strangeness enhancement as compared to other models. We conclude that adequately treating all the relevant effects and further retuning the models is necessary to explain the observed effects

Demystifying the nature of nuclear modification factor for upcoming O-O collisions at LHC energies using a transport model

International audienceThe present work focuses on Oxygen-Oxygen (O-O) collisions, which are planned at the CERN Large Hadron Collider. Oxygen, being a doubly magic number nucleus, has some very unique features. This study attempts to probe the exotic state of QCD matter in O-O collisions. Additionally, the role of different nuclear density profiles in governing the final state dynamics in ultra-relativistic nuclear collisions is also explored. Using a multi-phase transport (AMPT) model, we obtain the nuclear modification factor ($\rm R_{\rm AA}$ ) for all charged hadrons and identified particles for O-O collisions at $\sqrt{s_{\rm{NN}}}$ = 7 TeV. Furthermore, we investigate the behavior of $\rm R_{\rm AA}$ as a function of transverse momentum ($\rm p_{\rm T}$) for three centralities (most-central, mid-central, and peripheral) considering both $\alpha$-cluster and Woods-Saxon nuclear density profiles. We also extend this work to study the rapidity dependence of $\rm R_{\rm AA}$ for all charged hadrons. To better under our findings of O-O collisions, the results are confronted with the available data of $\rm R_{\rm AA}$ for Pb-Pb collisions. The present study sheds light on particle production mechanisms, emphasizing factors influencing particle yield from pre-collision to post-collision stages in the context of O-O collisions