# Beam energy dependence of (anti-)deuteron production in Au+Au collisions at RHIC

## TL;DR

This study examines how (anti-)deuteron production varies with collision energy in gold-gold collisions at RHIC, revealing insights into the medium's properties and the correlation volume of baryons and anti-baryons.

## Contribution

It provides the first systematic analysis of (anti-)deuteron production across a wide energy range at RHIC, highlighting the energy dependence of the coalescence parameter and potential signals of a change in the medium's equation of state.

## Key findings

- Deuteron yields are well described by the thermal model.
- Anti-deuteron coalescence parameter B2 is systematically lower than that for deuterons.
- B2 shows a broad minimum around 20-40 GeV, indicating possible changes in the medium's equation of state.

## Abstract

We report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at $\sqrt{s_\text{NN}} =\ $7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR experiment at RHIC. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter $B_2$ are discussed. We find that the values of $B_2$ for anti-deuterons are systematically lower than those for deuterons, indicating that the correlation volume of anti-baryons is larger than that of baryons at $\sqrt{s_\text{NN}}$ from 19.6 to 39 GeV. In addition, values of $B_2$ are found to vary with collision energy and show a broad minimum around $\sqrt{s_\text{NN}}=\ $20 to 40 GeV, which might imply a change of the equation of state of the medium in these collisions.