# Beam energy dependence of $d$ and $\bar{d}$ productions in Au+Au collisions at RHIC

## TL;DR

This study investigates how the production of deuterons and anti-deuterons varies with collision energy in gold-gold collisions at RHIC, revealing insights into the medium's freeze-out properties and possible phase transition signals.

## Contribution

It provides the first systematic measurement of deuteron and anti-deuteron production across a wide range of collision energies at RHIC, highlighting differences in correlation volumes and potential changes in the medium's equation of state.

## Key findings

- Anti-deuteron $B_2$ values are systematically lower than deuteron $B_2$ values.
- $B_2$ decreases with increasing collision energy, reaching a minimum around 20 GeV.
- Indicates a possible change in the medium's equation of state at this energy.

## Abstract

Light nuclei have much smaller binding energy compared to the temperature of the system created in heavy-ion collisions. Consequently, the distributions of light nuclei can be used to probe the freeze-out properties, such as correlation volume and local baryon density of the medium created in high-energy nuclear collisions. In this paper, we report the results of deuteron and anti-deuteron production in Au+Au collision at $\sqrt{s_\mathrm{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by STAR at RHIC. The collision energy, centrality and transverse momentum dependence of the coalescence parameter $B_2$ for deuteron and anti-deuteron production are discussed. We find the values of $B_2$ for anti-deuteron are systematically lower than those for deuterons indicating the correlation volume of anti-baryon are larger than that of baryon. In addition, the values of $B_2$ are found to decrease with increasing collision energy and reach a minimum around $\sqrt{s_\mathrm{NN}}$ = 20 GeV implying a change of the equation of state of the medium in these collisions.