Speaker
Description
The production mechanism of light (anti-)nuclei in heavy-ion collisions can be either by the thermal model or the coalescence model. By studying the yields and ratios of light (anti-)nuclei, we can gain insight into their production mechanism and physical properties of the expanding system at freeze-out. Furthermore, the enhancement in the light nuclei compound ratios such as $\rm N_t \times N_p/N_d^2$ and $\rm N_{^3He} \times N_p/N_d^2$ from the coalescence baseline, has been suggested as a potential probe to search for the critical phenomena in the QCD phase diagram. This enhancement might be a consequence of the enhanced baryon density fluctuations when the system is in vicinity of the critical point or the first-order phase transition. In the first phase of the Beam Energy Scan (BES-I) program at RHIC, an enhancement relative to the coalescence baseline of the light nuclei yield ratio ($\rm N_t \times N_p/N_d^2$) is observed in the most central Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 19.6 and 27 GeV with a combined significance of 4.1 $\sigma$. The large datasets ($\sim10 \times$BES-I) taken by the STAR BES-II with enhanced detector capabilities will greatly improve the precision of the new measurements.
In this talk, we will present the centrality and energy dependence of transverse momentum ($p_{\rm T}$) spectra of p, $\rm \bar{p}$, d, $\rm \bar{d}$, and $\rm ^3He$ in Au+Au collisions at BES-II energies of $\sqrt{s_{\rm NN}}$ = 7.7 – 27 GeV. We will also report the centrality and energy dependence of integrated particle yields ($\rm dN / dy$) and mean $p_{\rm T}$ ($ \langle p_{\rm T} \rangle $) of light nuclei. We will discuss the centrality and pT dependence of the coalescence parameters ($B_2(\rm d)$ and $B_3 (\rm ^3He))$. The physics implications of these results will be discussed.
