Effect of baryon density on parton production, chemical equilibration and thermal photon emission from quark gluon plasma

Abstract

The effect of baryon density on parton production processes of $gg\rightleftharpoons ggg$ and $gg\rightleftharpoons q{\bar q}$ is studied using full phase space distribution function and also with inclusion of quantum statistics i.e. Pauli blocking and Bose enhancement factors, in the case of both saturated and unsaturated quark gluon plasma. The rate for the process $gg \rightleftharpoons q{\bar q}$ is found to be much less as compared to the most commonly used factorized result obtained on the basis of classical approximation. This discrepancy, which is found both at zero as well as at finite baryon densities, however, is not due to the lack of quantum statistics in the classical approximation, rather due to the use of Fermi-Dirac and Bose-Einstein distribution functions for partons instead of Boltzmann distribution which is appropriate under such approximation. Interestingly, the rates of parton production are found to be insensitive to the baryo-chemical potential particularly when the plasma is unsaturated although the process of chemical equilibration strongly depends on it. The thermal photon yields, have been calculated specifically from unsaturated plasma at finite baryon density. The exact results obtained numerically are found to be in close agreement with the analytic expression derived using factorized distribution functions appropriate for unsaturated plasma. Further, it is shown that in the case of unsaturated plasma, the thermal photon production is enhanced with increasing baryon density both at fixed temperature and fixed energy density of the quark gluon plasma.