Direct photons: A nonequilibrium signal of the expanding quark-gluon plasma at RHIC energies
Year: 2001
Type: preprint
Abstract: Direct photon production from a longitudinally expanding quark-gluon plasma (QGP) at Relativistic Heavy Ion Collider (RHIC) energies is studied with a real-time kinetic description that is consistently incorporated with hydrodynamics. Within Bjorken's hydrodynamical model, energy nonconserving (anti)quark bremsstrahlung q (\\bar{q}) \\to q (\\bar{q}) \\gamma and quark-antiquark annihilation q \\bar{q} \\to \\gamma are shown to be the dominant nonequilibrium effects during the transient lifetime of the QGP. For central Au+Au collisions at RHIC energies \\sqrt{s} ~ 200A GeV, we find a significant excess of direct photons in the range of transverse momentum p_T \\gtrsim 1.0-1.5 GeV/c as compared to equilibrium results. The transverse momentum distribution at midrapidity falls off with a power law p_T^{-\\nu} with 2.5 \\lesssim \\nu \\lesssim 3.0 as a consequence of these off-shell processes, providing a distinct experimental nonequilibrium signature. The rapidity distribution is fairly flat in the interval |y| \\lesssim 2. The power law exponent \\nu increases with the initial temperature of the QGP and therefore with the total multiplicity rapidity distribution dN_\\pi/dy.
Source: arXiv (Cornell University)
Authors: Shang-Yung Wang, D. Boyanovsky, Kin‐Wang Ng
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2949232058