Elliptic flow of thermal photons and formation time of quark gluon plasma at energies available at the BNL Relativistic Heavy Ion Collider (RHIC)

Abstract

We calculate the elliptic flow of thermal photons from $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC energies for a range of values for the formation time ${\ensuremath{\tau}}_{0}$ but a fixed entropy (or particle rapidity density). The results are found to be quite sensitive to ${\ensuremath{\tau}}_{0}$. The value of ${v}_{2}$ for photons decreases as ${\ensuremath{\tau}}_{0}$ decreases and admits a larger contribution from the quark gluon plasma phase, which has a smaller ${v}_{2}$. The elliptic flow coefficient for hadrons, however, is only marginally dependent on ${\ensuremath{\tau}}_{0}$.