arXiv subjects

Sourav Sarkar

Publications and source records attributed to Sourav Sarkar.

167 records · Page 10Linked to original sources

arXiv1997

Quark Gluon Plasma Diagnostics in a Successive Equilibrium Scenario

The relativistic Fokker Planck equation has been used to study the evolution of the quark distribution in the quark gluon phase expected to be formed in ultra-relativistic heavy ion collisions. The effect of thermal masses for quarks and gluons is incorporated to take account of the in-medium properties. We find that the kinetic equilibrium is achieved before the system reaches the critical temperature of quark hadron phase transition. We find that chemical equilibrium is not achieved during this time. We have evaluated the electromagnetic probes of quark gluon plasma from the non-equilibrated quark gluon phase and compared them with those in completely equilibrated scenario. The hard QCD production rates for the electromagnetic ejectiles as well as the heavy quark production rates are also calculated.

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arXiv1997

Large Mass Diphotons From Relativistic Heavy Ion Collisions

We evaluate the production of large mass diphotons from quark annihilation at BNL RHIC and CERN LHC energies from central collisions of gold nuclei. The collision is assumed to lead to either a thermally and chemically equilibrated quark gluon plasma, or a free-streaming quark gluon gas having an identical initial entropy, or a chemically equilibrating quark gluon system, with the same entropy at $T=T_c$. We also obtain an estimate of hard photon pairs from initial state quark annihilation and find that the thermal production dominates the yield up to $M \approx$ 4 GeV at RHIC, and up to 6 GeV at LHC. A simulation study of decay versus thermal diphotons is presented.

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arXiv1996

Thermal Masses and Equilibrium Rates in the Quark Gluon Phase

We apply the momentum integrated Boltzmann transport equation to study the time evolution of various quark flavours in the central region of ultra-relativistic heavy ion collisions. The effects of thermal masses for quarks and gluons are incorporated to take into account the in-medium properties of these ingredients of the putative quark gluon plasma. We find that even under very optimistic conditions, complete chemical equilibration in the quark gluon plasma appears unlikely.

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arXiv1996

Soft Electromagnetic Radiations from Relativistic Heavy Ion Collisions

The production of low mass dileptons and soft photons from thermalized Quark Gluon Plasma (QGP) and hadronic matter in relativistic heavy ion collisions is evaluated. A boost invariant longitudinal and cylindrically symmetric transverse expansion of the systems created in central collision of lead nuclei at CERN SPS, BNL RHIC, and CERN LHC, and undergoing a first order phase transition to hadronic matter is considered. A large production of low mass (M< 0.3 GeV) dileptons, and soft photons (p_T< 0.4 GeV) is seen to emanate from the bremsstrahlung of quarks and pions. We find an increase by a factor of 2--4 in the low mass dilepton and soft photon yield as we move from SPS to RHIC energies, and an increase by an order of magnitude as we move from SPS to LHC energies. Most of the soft radiations are found to originate from pion driven processes at SPS and RHIC energies, while at the LHC energies the quark and the pion driven processes contribute by a similar amount. The study of the transverse mass distribution is seen to provide interesting details of the evolution. We also find a unique universal behaviour for the ratio of M^2 weighted transverse mass distribution for M= 0.1 GeV to that for M= 0.2 and 0.3 GeV, as a function of M_T, for SPS, RHIC, and LHC energies, in the absence of transverse expansion of the system. A deviation from this universal behaviour is seen as a clear indication of the flow.

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arXiv1996

Dissipative Effects in Photon Diagnostics of Quark Gluon Plasma

The effects of dissipation on the space time evolution of matter formed in ultra-relativistic heavy ion collision is discussed. The thermal photon spectra for RHIC and LHC energies with viscous flow is considered. The effects of viscosity in the thermal single photon spectra is seen to be important in QGP phase as compared to the hadronic phase. Recently available data from WA80 group at SPS energies for $S+Au$ collision are compared with theoretical calculations. The experimental data do not appear to be compatible with the formation of matter in the pure hadronic phase.

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