ALP photo-production in the parton and hadron cascade model PACIAE

Abstract

In this work, the parton and hadron cascade model PACIAE is employed to simulate the events of Au+Au collisions at $\sqrt{s_{NN}}=$200 GeV within the 60-80 \% centrality interval. Based on the abundant photons in final hadronic state, the statistical-mechanics-based coalescence model DCPC is applied to phenomenologically recombine post-freeze-out photon pairs into axion-like particles (ALPs) for the first time. The coalescence probability is constrained by the branching-ratio $B_r(a\to \gamma \gamma )=0.57$ under the threshold of twice of $K$ meson mass. The ALP observables including yields, transverse-momentum distributions and rapidity spectra are calculated for several benchmark ALP-mass bins. These theoretical predictions are worthy to be investigated by the experiments.