Searcharxiv⌕ Search

arXiv subjects

Waseem Bashir

Publications and source records attributed to Waseem Bashir.

7 recordsLinked to original sources
arXiv2022

Particle Ratios in a Multi Component Non-Ideal Hadron Resonance Gas

We have considered formation of a multi component non-ideal hot and dense gas of hadronic resonances in the ultra-relativistic heavy-ion collisions. In the statistical thermal model approach the equation of state (EoS) of the non interacting ideal hadron resonance gas (IHRG) does not incorporate either the attractive part or the short range repulsive part of the baryonic interaction. On the other hand in the non-ideal hadron resonance gas (NIHRG) model we can incorporate these interactions using the Van der Waals (VDW) type approach. Studies have been made to see its effect on the critical parameters of the quark-hadron phase transition. However, it can also lead to modifications in the calculated relative particle yields. In this paper we have attempted to understand the effect of such Van der Waals type interactions on the relative particle yields and also studied their dependences on the system thermal parameters, such as the temperature and baryon chemical potential (μ_B). We have also taken into account the decay contributions of the heavier resonances. These results on particle ratios are compared with the corresponding results obtained from the point-like i.e. non interacting IHRG model. It is found that the particle ratios get modified by incorporating the Van der Waals type interactions, especially in a baryon rich system which is expected to be formed at lower RHIC energies, SPS energies and in the forthcoming CBM experiments due to high degree of nuclear stopping in these experiments.

hep-ph↗
arXiv2014

Systematic of Particle Thermal Freeze-out in a Hadronic Fireball at RHIC

We attempt to describe the rapidity and transverse momentum spectra of strange as well as non-strange hadrons e.g. cascade,cascadebar, lambda , lambdabar, proton, protonbar,(omega+omegabar, Kaon, anti-Kaon and their ratios in the ultra-relativistic collisions of gold nuclei at (Root sNN)=200 GeV. This is done by using a statistical thermal freeze-out model which incorporates the rapidity (collision) axis as well as transverse direction boosts developed within an expanding hot and dense hadronic fluid (fireball) till the final freeze-out. We determine the thermo-chemical freeze-out conditions particularly in terms of the temperature, baryon chemical potential and collective flow effect parameters for different particle species. The parameters indicate occurrence of freeze-out of the singly and doubly strange hyperon species at somewhat earlier times during the evolution of the fireball. The experimental data of the transverse momentum and rapidity distribution are well reproduced. The contribution of heavier hadronic resonance decay is taken into account.

hep-ph↗
arXiv2012

Finite Size Corrected Relativistic Mean-Field Model and QCD Critical End Point

The effect of finite size of hadrons on the QCD phase diagram is analyzed using relativistic mean field model for the hadronic phase and the Bag model for the QGP phase. The corrections to the EOS for hadronic phase are incorporated in a thermodynamic consistent manner for Van der Waals like interaction. It is found that the effect of finite size of baryons is to shift CEP to higher chemical potential values.

hep-ph↗
arXiv2012

Transport Coefficients in Quasi-particle Models

We study the non-equilibrium properties of a dynamical fluid composed of quasi-particles whose mass is temperature and charge chemical potential dependent, in kinetic theory under the relaxation time approximation. In particular we calculate the scaling behaviour of bulk viscosity `$ζ$' near the QCD chiral phase transition in the 3d $\it O$(2) universality class. It is found that the bulk viscosity `$ζ$' does not show a divergent behaviour near the QCD chiral phase transition. This scaling behaviour of `$ζ$' prevails in the presence of Gold-stone modes that arise due to the explicit breaking of continuous $\it O$(4) symmetry. On contrary these modes have a significant effect on the scaling behaviour of specific heat $C_V$ which diverges at the critical temperature $T_C$.

hep-ph↗
arXiv2012

Quark-hadron Phase Transition in Relativistic Mean-field Model

We have studied the quark-hadron phase transition with RMFT motivated equation of state for a strongly interacting hadronic sector and lattice motivated equation of state for weakly interacting QGP sector. The interactions in hadronic sector are dominated by the exchange of scalar and vector mesons (σ_ σ, ω, ρ, ϕ) thereby allowing this phase to be modeled by the interacting baryonic, pionic and Kaonic fields. The pionic and Kaonic fields are incorporated on equal footing to baryonic field rather than including pions and Kaons as exchange particles only. The effect of interactions on quark-hadron phase transition curve was studied using Gibbs criteria for phase equilibrium. It was found that the first order quark hadron phase transition curve ends at a critical point, whose coordinates coincide with that of lattice gauge theory result involving lattice re-summation technique.

hep-ph↗
arXiv2011

A Unified Approach towards Describing Rapidity and Transverse Momentum Distributions in Thermal Freeze-Out Model

We have attempted to describe the rapidity and transverse momentum spectra, simultaneously, of the hadrons produced in the Ultra-relativistic Nuclear Collisions. This we have tried to achieve in a single statistical thermal freeze-out model using single set of parameters. We assume the formation of a hadronic gas in thermo-chemical equilibrium at the freeze-out. The model incorporates a longitudinal as well as a transverse hydrodynamic flow. We have also found that the role of heavier hadronic resonance decay is important in explaining the particle spectra.

hep-ph↗