Effects of pion potential and nuclear symmetry energy on the $\pi^{-}/\pi^{+}$ ratio in heavy-ion collisions at beam energies around the pion production threshold

TL;DR

This study uses the IBUU transport model to analyze how pion potential and nuclear symmetry energy influence the -/+ ratio in heavy-ion collisions near the pion production threshold, revealing energy-dependent effects.

Contribution

It provides new insights into the energy-dependent effects of pion potential and symmetry energy on pion ratios in heavy-ion collisions near the pion production threshold.

Findings

Pion potential affects the -/+ ratio differently at low and high pion energies.

The impact of pion potential on the total -/+ ratio increases at energies below the pion threshold.

Pion potential reduces the influence of symmetry energy on the -/+ ratio below the pion threshold.

Abstract

Within the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU) transport model, we studied the effects of the pion potential and the symmetry energy on the pion production in the central $^{197}Au+^{197}Au$ collisions around the pion production threshold. It is found that the pion potential has opposite effects on the value of $\pi^-/\pi^+$ ratio at low and high pion energies. The effect of the pion potential on the total $\pi^-/\pi^+$ ratio becomes larger in heavy-ion collisions at beam energies below the pion production threshold. And at beam energies below the pion production threshold, with the pion potential, the effect of the symmetry energy on the $\pi^-/\pi^+$ ratio becomes smaller compared with that above the pion production threshold.