Parametrization of the nucleus-nucleus gamma-ray production cross sections below 100 GeV/nucleon: Subthreshold pions and Hard photons

TL;DR

This paper develops new parametrizations for gamma-ray and electron-positron production cross sections from subthreshold nuclear collisions below 100 GeV/nucleon, enabling accurate modeling of astrophysical gamma-ray spectra below 1 GeV.

Contribution

It introduces the first accurate parametrizations for subthreshold pion and hard photon production cross sections, extending previous models to energies up to 100 GeV/nucleon.

Findings

Parametrizations agree well with experimental data.

Enables detailed studies of gamma-ray spectra below 1 GeV.

Extends pion contribution models to higher energies.

Abstract

"Subthreshold pions" and so-called "hard photons" are two important channels for producing less than 1 GeV $\gamma$-rays and $e^\pm$ pairs from nuclear collisions with energy per nucleon below the $\pi$-meson production threshold. I use publicly available experimental data to parametrize these two channels' $\gamma$-ray and $e^\pm$ production cross sections and extend the pion contribution to these particles spectra at higher energies using their corresponding spectra from $pp$ interactions. These parametrizations are valid for collision energy $T_p\leq 100$ A GeV and agree reasonably well with the available experimental data. The new parametrizations allow, for the first time, accurate studies of astrophysical $\gamma$-rays below 1 GeV.