arXiv subjects
Publications and source records attributed to Saeed Uddin.
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.
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 $T_C$.
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.
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.
We use the extended statistical thermal model to describe various hadron rapidity spectra at the highest RHIC energy (200 GeV/A). The model assumes the formation of hot and dense regions moving along the beam axis with increasing rapidities, yFB. It has been earlier shown that this model can explain the net proton flow i.e. p minus pbar, ratio pbar/p and the pion rapidity spectra. In this paper we have attempted to show that in addition to these quantities, this model can also successfully describe the individual rapidity spectra of protons, antiprotons, Kaons, antiKaons, pions, the ratios lambdabar/lambda and cascadebar/cascade. The experimental data set on p, pbar, K, Kbar and Pion provided by BRAHMS collaboration at the highest energy of Relativistic Heavy Ion Collider, sqrt(SNN) = 200 GeV are used. The theoretical results fit quite well with mid-rapidity data (for y < 1) of the lambdabar/lambda and the cascadebar/cascade ratios available (from STAR). We have used single set of model parameters including single value of the temperature parameter T for all the regions of the hot and dense matter formed. The chemical potentials are however assumed to be dependent on the fireball rapidity yFB. We have analyzed the contribution of the decay of the heavier resonances to the proton (antiproton) rapidity spectra. It is found that the rapidity spectrum of the product hadron is nearly same as that of the parent hadron. We have also imposed the criteria of exact strangeness conservation in every (local) region of the dense matter separately, which is necessary. We also discuss what can be learned about the nuclear transparency effect at the highest RHIC energy from the net proton rapidity distribution.
Recently Beccattini and Cleymamns have proposed a model to understand the p-pbar data obtained at RHIC and SPS. We have shown that this model has a much greater applicability and can very well be used to describe the rapidity spectra of protons and antiprotons separately measured at the highest energy of Relativistic Heavy Ion Collider i.e., 200 GeV/A by BRAHMS Collaboration. We have also determined that the contribution of the decay products of the heavier resonances like delta, lambda etc. actually dominate over the protons (antiprotons) of pure thermal origin. We have also imposed the criteria of exact strangeness conservation in each fireball separately. It is shown that it is possible to explain not only the p-pbar data but the complete set of data viz. the rapidity distributions of protons, antiprotons and the ratio pbar/p simultaneously quite well with a single set of model parameters which includes a single value of the temperature parameter T chosen for all the fireballs. We have also fitted the Kaon rapidity spectra obtained by BRAHMS collaboration in the same experiment. This is unlike the previous analyses wherein a varying temperature has been assumed for the fireballs formed along the rapidity axis. The chemical potentials are however assumed to be dependent on the fireball rapidity yfb.