Finite-Density Dynamics of Chemically Equilibrating QGP in Conformal Gubser Flow and Hard Thermal Photon Production

Abstract

We study the chemical equilibration of a hot and dense quark-gluon plasma (QGP) at finite baryon density produced in relativistic heavy-ion collisions within conformal Gubser flow. Chemical non-equilibrium is incorporated through fugacity parameters in the parton phase-space distribution functions, whose evolution is governed by master rate equations coupled to the hydrodynamic expansion with transverse flow. We analyse the interplay between chemical equilibration and finite-density dynamics, and investigate its impact on hard thermal photon production. We observe that both finite density and transverse expansion delay chemical equilibration, leading to a chemically undersaturated medium with quarks lagging behind gluons. While the overall thermal photon yield from the expanding system is suppressed in the non-equilibrium scenario, we find an enhanced early-time contribution to high $p_T$ photon production. By analyzing the instantaneous photon emission in presence of chemical non-equilibrium, we demonstrate that the rates exhibit a distinct temporal structure arising from the interplay of rapid cooling and evolving fugacities. These features may provide potential observable signatures of chemical equilibration dynamics in the QGP.

21 pages, 19 figures; Accepted for publication in J. Phys. G

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