Flow fluctuations and kinetic freeze-out of identified hadrons at energies available at the CERN Super Proton Synchrotron

We investigate the effect of flow fluctuations, incorporated in non boost-invariant blast-wave model, on kinetic freeze-out parameters of identified hadrons in low energy relativistic heavy-ion collisions. For the purpose of this study, we use the transverse momentum spectra of the identified hadrons produced in central Pb--Pb collisions, at SPS energies ranging from $\rm E_{Lab}=20A-158A$ GeV, and analyze them within a modified non boost-invariant blast wave model. We perform simultaneous fits of the transverse momentum spectra for light hadrons ($\pi^{-}$, $K^{\pm}$, $p$) and heavy strange hadrons ($\Lambda$, $\bar{\Lambda}$, $\phi$, $\Xi^{\pm}$, $\Omega^{\pm}$) seperately. We also fit the transverse momentum spectra of charmonia ($J/\Psi$, $\Psi'$) at $\rm E_{Lab}=158A$ GeV. Our findings suggest that the inclusion of flow fluctuations enhances kinetic freeze-out temperature in case of light and heavy strange hadrons and reduces the corresponding transverse flow velocities. Moreover, we find that the kinetic freeze-out parameters of the charmonia at $\rm E_{Lab}=158A$ GeV are least affected by inclusion of flow fluctuations. Based on this, we make predictions which can provide further insights on the role of flow fluctuations in relativistic heavy-ion collisions.Comment: 11 pages, 8 figures, Accepted in Phys. Rev. C, Version to appear in the journa

Anisotropic flow of charged and identified hadrons at FAIR energies and its dependence on the nuclear equation of state

In this article, we examine the equation of state (EoS) dependence of the anisotropic flow parameters ($v_{1}$, $v_{2}$ and $v_{4}$) of charged and identified hadrons, as a function of transverse momentum ($p_{\rm T}$), rapidity ($y_{c.m.}$) and the incident beam energy ($\rm E_{\rm Lab}$) in mid-central Au + Au collisions in the energy range $\rm E_{\rm Lab} = 6 -25$ A GeV. Simulations are carried out by employing different variants of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, namely the pure transport (cascade) mode and the hybrid mode. In the hybrid mode, transport calculations are coupled with the ideal hydrodynamical evolution. Within the hydrodynamic scenario, two different equations of state (EoS) viz. Hadron gas and Chiral + deconfinement EoS have been employed separately to possibly mimic the hadronic and partonic scenarios, respectively. It is observed that the flow parameters are sensitive to the onset of hydrodynamic expansion of the fireball in comparison to the pure transport approach. The results would be useful as predictions for the upcoming low energy experiments at Facility for Antiproton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA).Comment: Accepted in European Physical Journal

Effect of various particlization scenarios on anisotropic flow and particle production using UrQMD hybrid model

We discuss the effect of various particlization scenarios available in the hybrid ultrarelativistic quantum molecular dynamics (UrQMD) event generator on different observables in non-central ($b$ $=$ 5--9 $fm$) Au + Au collisions in the beam energy range 1A-158A GeV. Particlization models switch fluid dynamic description to the transport description using various hypersurface criteria. In addition to particlization models, various equations-of-state (EoS) provided by the UrQMD hybrid model were employed. The observables examined in this paper include the excitation function of anisotropic coefficients such as directed ($v_{1}$) and elliptic flow ($v_{2}$), particle ratios of the species, and the shape of net-proton rapidity spectra at mid-rapidity. The results obtained here can help predict and compare the measurements provided by future experiments at the Facility for Antiproton and Ion Research (FAIR) and the Nuclotron-based Ion Collider fAcility (NICA) once the data becomes available. We also study the most suitable combination of the particlization model and EoS, which best describes the experimental measurements.Comment: 11 pages, 8 figure

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

Electrons from Charm and Beauty Quarks in Proton-Proton Collisions with ALICE at the LHC and Study of Collective Flow in Low Energy Heavy-Ion Collisions

In this thesis, an attempt is made to explore the properties of the medium that can be formed in low as well as high energy nuclear collisions. In the context of high energy collisions, the measurements of electrons from charm and beauty quarks in proton-proton collisions are performed using the data provided by ALICE experiment where the matter with very high temperature and almost zero baryonic chemical potential is believed to be produced. For these measurements, different analysis techniques are adopted and the results are compared with the theoretical predictions which show consistency. In the view of ongoing ALICE detector upgrade, the improved primary vertex and impact parameter resolution, together with the improved luminosity of the LHC accelerator complex, will provide a chance to perform the precision measurements. Moreover, the new measurements of the species such as $\Lambda_{b}$ baryon and $B$ meson would be possible. In the later part, the focus is shifted to the other end of the QCD phase diagram, i.e. to study the matter produced in moderate temperature and high net baryon density regime. The mass-dependent hierarchy in the kinetic freeze-out parameters of light hadrons, heavy strange hadrons and charmonia produced in central low energy nuclear collisions are examined in the framework of the non-boost-invariant blast-wave model. Similar hierarchy in the speed of sound of light hadrons and heavy strange hadrons is observed when their rapidity spectra are studied using the non-conformal solution of the Landau hydrodynamical model. For the upcoming experiments at FAIR and NICA accelerator facilities, these measurements would be useful for a better understanding of the freeze-out conditions. Moreover, a simulation study of different anisotropic flow coefficients of charged hadrons in non-central nuclear collision at FAIR energies is performed using the UrQMD model which will also be very crucial once the data from experiments at FAIR and NICA will be available

Production of electrons from heavy-flavour hadron decays in different collision systems with ALICE at LHC

Heavy-flavour quarks, due to their large masses, are produced in the early stages of the relativistic heavy-ion collisions via initial hard scatterings. Therefore, as they experience the full system evolution, heavy quarks are effective probes of the hot and dense medium created in such collisions. In pp collisions, the measurement of heavy-flavour hadron production cross sections can be used to test our understanding of the Quantum ChromoDynamics (QCD) in the perturbative regime. Also, pp collisions provide a crucial reference for the corresponding measurements in larger systems. In Pb--Pb (Xe--Xe) collisions, the measurement of the nuclear modification factor of heavy-flavour hadrons provides information on the modification of the invariant yield with respect to pp collisions due to the produced cold and hot QCD matter. The possible mass dependence of the parton energy loss can be studied by comparing the $R_{\rm AA}$ of pions, charm and beauty hadrons. In this contribution, recent results from ALICE at the LHC are reported with focus on the different measurements of the heavy-flavour electrons in pp collisions at 2.76, 5.02, 7 and 13 TeV and in Pb--Pb (Xe--Xe) collisions at 5.02 (5.44) TeV. The results include the differential production cross sections and nuclear modification factors of heavy-flavour electrons at mid-rapidity. The comparison of experimental data with model predictions is discussed