Azimuthal asymmetry of direct photons in intermediate energy heavy-ion collisions

TL;DR

This paper presents the first calculation of azimuthal asymmetry in direct photons emitted from intermediate energy heavy-ion collisions, revealing anti-correlated flow patterns with free protons.

Contribution

It introduces a novel calculation of azimuthal asymmetry parameters for hard photons, providing insights into early-stage nuclear matter dynamics.

Findings

Positive directed flow parameter $F$ for photons

Negative elliptic asymmetry coefficient $v_2$ for photons

Anti-correlation between photon and proton flow patterns

Abstract

Hard photon emitted from energetic heavy ion collisions is of very interesting since it does not experience the late-stage nuclear interaction, therefore it is useful to explore the early-stage information of matter phase. In this work, we have presented a first calculation of azimuthal asymmetry, characterized by directed transverse flow parameter $F$ and elliptic asymmetry coefficient $v_2$, for proton-neutron bremsstrahlung hard photons in intermediate energy heavy-ion collisions. The positive $F$ and negative $v_2$ of direct photons are illustrated and they seem to be anti-correlated to the corresponding free proton's flow.