Jet Transport Coefficient at the Large Hadron Collider Energies in a Color String Percolation Approach

Within the color string percolation model (CSPM), jet transport coefficient, $\hat{q}$, is calculated for various multiplicity classes in proton-proton and for centrality classes in nucleus-nucleus collisions at the Large Hadron Collider energies for a better understanding of the matter formed in ultra-relativistic collisions. $\hat{q}$ is studied as a function of final state charged particle multiplicity, initial state percolation temperature and energy density. The CSPM results are then compared with different theoretical calculations from the JET collaboration those incorporate particle energy loss in the medium. A good agreement is found between CSPM results and the JET collaboration calculations.Comment: 8 pages and 7 figures, Submitted for publicatio

Diffusion and fluctuations of open charmed hadrons in an interacting hadronic medium

Heavy quarks are excellent probes to understand the hot and dense medium formed in ultra-relativistic collisions. In a hadronic medium, studying the transport properties, e.g. the drag ($\gamma$), momentum diffusion ($B_{0}$), and spatial diffusion ($D_{s}$) coefficients of open charmed hadrons can provide useful information about the medium. Moreover, the fluctuations of charmed hadrons can help us to locate the onset of their deconfinement. In this work, we incorporate attractive and repulsive interactions in the well-established van der Waals hadron resonance gas model (VDWHRG) and study the diffusion and fluctuations of charmed hadrons. This study helps us understand the importance of interactions in the system, which significantly affect both the diffusion and fluctuations of charmed hadrons.Comment: 11 pages and 8 captioned figures. Submitted for publicatio

Formation of a Perfect Fluid in pppp, pp-Pb, Xe-Xe and Pb-Pb Collisions at the Large Hadron Collider Energies

Isothermal compressibility ($\kappa_{\rm T}$) is an important thermodynamic observable which gives information about the deviation of a fluid from a perfect fluid. In this work, for the first time we have estimated the isothermal compressibility of QCD matter formed in high energy hadronic and nuclear collisions using color string percolation model (CSPM), where we investigate the change in $\kappa_{\rm T}$ as a function of final state charged particle multiplicity across various collision species. We have also estimated the initial percolation temperature for different collision systems at different collision energies, which helps us to have a better understanding of the system at the initial phase of evolution. The comparison of the CSPM results for isothermal compressibility with that for the well known fluids, indicates that the matter formed in heavy-ion collisions might be the {\it closest perfect fluid} found in nature. This estimation complements the well-known observation of minimum shear viscosity to entropy density ratio for a possible QGP medium created in heavy-ion collision experiments. Also, a threshold of pseudorapidity density of charged particles, $dN_{\rm ch}/d\eta \simeq 10$ is found for a possible QGP formation at the LHC energies.Comment: Xe-Xe data are added to this versio

Thermodynamics of a rotating hadron resonance gas with van der Waals interaction

Studying the thermodynamics of the systems produced in ultra-relativistic heavy-ion collisions is crucial in understanding the QCD phase diagram. Recently, a new avenue has opened regarding the implications of large initial angular momentum and subsequent vorticity in the medium evolution in high-energy collisions. This adds a new type of chemical potential into the partonic and hadronic systems, called the rotational chemical potential. We study the thermodynamics of an interacting hadronic matter under rotation, formed in an ultra-relativistic collision. We introduce attractive and repulsive interactions through the van der Waals equation of state. Thermodynamic properties like the pressure ($P$), energy density ($\varepsilon$), entropy density ($s$), trace anomaly ($(\varepsilon - 3P)/T^{4}$), specific heat ($c_{\rm v}$) and squared speed of sound ($c_{\rm s}^{2}$) are studied as functions of temperature ($T$) for zero and finite rotation chemical potential. The charge fluctuations, which can be quantified by their respective susceptibilities, are also studied. The rotational (spin) density corresponding to the rotational chemical potential is explored. In addition, we explore the possible liquid-gas phase transition in the hadron gas with van der Waals interaction in the $T$ -- $\omega$ phase space.Comment: 11 pages and 6 captioned figures. Submitted for publicatio

Proton number cumulants in a modified van der Waals hadron resonance gas

An estimate of the proton number cumulants in the hadronic matter is presented considering a van der Waals-type interaction between the constituent particles. We argue that the attractive and repulsive parameters in the VDW hadron resonance gas (VDWHRG) model change as functions of baryochemical potential ($\mu_{B}$) and temperature ($T$). This, in turn, affects the estimation of thermodynamic properties and, consequently, the conserved charge fluctuations. We employ a simple parametrization to bring in the center-of-mass energy ($\sqrt{s_{\rm NN}}$) dependence on temperature and baryochemical potential and then estimate the proton number cumulants with the modified approach. The modified van der Waals hadron resonance gas model (MVDWHRG) explains the existing experimental data very well.Comment: 9-pages and 6-captioned figures, Submitted for publicatio

Effect of magnetic field on the optical and thermodynamic properties of a high-temperature hadron resonance gas with van der Waals interactions

We study the behavior of a hadronic matter in the presence of an external magnetic field within the van der Waals hadron resonance gas (VDWHRG) model, considering both attractive and repulsive interactions among the hadrons. Various thermodynamic quantities like pressure ($P$), energy density ($\varepsilon$), magnetization ($\mathcal{M}$), entropy density ($s$), squared speed of sound ($c_{\rm s}^{2}$), specific heat capacity at constant volume ($c_{v}$) are calculated as functions of temperature ($T$) and static finite magnetic field ($eB$). We also consider the effect of baryochemical potential ($\mu_{B}$) on the above-mentioned thermodynamic observables in the presence of a magnetic field. Further, we estimate the magnetic susceptibility ($\chi_{\rm M}^{2}$), relative permeability ($\mu_{\rm r}$), and electrical susceptibility ($\chi_{\rm Q}^{2}$) which can help us to understand the system better. With the information of $\mu_{\rm r}$ and dielectric constant ($\epsilon_{r}$), we enumerate the refractive index ($RI$) of the system under consideration. Through this model, we quantify a liquid-gas phase transition in the T-eB-$\mu_B$ phase space.Comment: 18 pages and 5-captioned figures. Submitted for publicatio

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