Effects of nuclear symmetry energy on eta meson production and its rare decay to the dark U-boson in heavy-ion reactions

TL;DR

This study investigates how nuclear symmetry energy influences eta meson production and its decay to dark U-bosons in heavy-ion collisions, highlighting sensitivity at sub-threshold energies and providing estimates for U-boson production cross sections.

Contribution

It demonstrates the sensitivity of eta meson yields to nuclear symmetry energy at certain energies and estimates U-boson production cross sections in heavy-ion reactions.

Findings

Eta meson yield is highly sensitive to symmetry energy at sub-threshold energies.

Sensitivity to symmetry energy diminishes above 5 GeV/nucleon.

Estimated maximum U-boson production cross section in heavy-ion collisions.

Abstract

Using a relativistic transport model ART1.0, we explore effects of nuclear symmetry energy on eta meson production and its rare decay to the dark U-boson in heavy-ion reactions from 0.2 to 10 GeV/nucleon available at several current and future facilities. The yield of eta mesons at sub-threshold energies is found to be very sensitive to the density dependence of nuclear symmetry energy. Above a beam energy of about 5 GeV/nucleon in Au+Au reactions, the sensitivity to symmetry energy disappears. Using the branching ratio of the rare eta decay (eta->gamma U) available in the literature, we estimate the maximum cross section for the U-boson production in the energy range considered, providing a useful reference for future U-boson search using heavy-ion reactions.