Azimuthal anisotropy and multiplicities of hard photons and free nucleons in intermediate-energy heavy-ion collisions

TL;DR

This study uses the IQMD model to analyze azimuthal anisotropy and multiplicities of hard photons and free nucleons in intermediate-energy heavy-ion collisions, revealing their flow behaviors and correlations.

Contribution

It is the first to systematically investigate the flow and multiplicity correlations of thermal photons and free nucleons in such collisions using the IQMD model.

Findings

Thermal photons exhibit directed and elliptic flow behaviors.

Incident energy dependence of photon flows confirms their role as probes.

Positive correlation between direct photon and free nucleon emission, anti-correlation for thermal photons.

Abstract

Anisotropic flow can offer significant information of evolution dynamics in heavy-ion collisions. A systematic study of the directed flow $v_1$ and elliptic flow $v_2$ of hard photons and free nucleons is performed for $^{40}$Ca+$^{40}$Ca collisions in a framework of isospin dependent quantum molecular dynamics (IQMD) model. The study firstly reveals that thermal photons emitted in intermediate-energy heavy-ion collisions have the behaviors of directed and elliptic flows. The interesting phenomena of incident energy dependence of $v_1$ and $v_2$ for thermal photons in central collisions also confirmed that it can be regarded as a good probe of evolution dynamics. Moreover, the multiplicities of hard photons and free nucleons and their correlation are also investigated. We find that direct photon emission is positively related to free nucleons emission, however, there exists an anti-correlation for thermal photons with free nucleons.