Elliptic flow of thermal photons and formation time of quark gluon plasma at RHIC

TL;DR

This paper investigates how the elliptic flow of thermal photons in RHIC collisions depends on the quark-gluon plasma formation time, revealing significant sensitivity that can inform understanding of early collision dynamics.

Contribution

It provides a detailed calculation of photon elliptic flow sensitivity to formation time, highlighting differences from hadronic flow behavior.

Findings

Photon v2 decreases with shorter formation times

Photon elliptic flow is more sensitive to QGP phase contributions

Hadron v2 shows marginal dependence on formation time

Abstract

We calculate the elliptic flow of thermal photons from Au+Au collisions at RHIC energies for a range of values for the formation time $\tau_0$ but fixed entropy (or particle rapidity density). The results are found to be quite sensitive to $\tau_0$. The $v_2$ for photons decreases as $\tau_0$ decreases and admits a larger contribution from the QGP phase which has a smaller $v_2$. The elliptic flow coefficient for hadrons, on the other hand, is only marginally dependent on $\tau_0$.