Beam Energy Dependence of Triton Production and Yield Ratio ($\mathrm{N}_t \times \mathrm{N}_p/\mathrm{N}_d^2$) in Au+Au Collisions at RHIC

The STAR Collaboration

Published 2022-09-16Version 1

We report the triton ($t$) production in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7 -- 200 GeV measured at mid-rapidity ($|y| <$ 0.5) by the STAR experiment from the first phase of the beam energy scan at the Relativistic Heavy Ion Collider (RHIC). The nuclear compound yield ratio ($\mathrm{N}_t \times \mathrm{N}_p/\mathrm{N}_d^2$), which is predicted to be sensitive to the local density fluctuation of neutrons, monotonically decreases with increasing charged-particle multiplicity ($dN_{ch}/d\eta$) and exhibits a scaling behavior. The multiplicity dependence of the yield ratios are compared with calculations from coalescence and thermal models. Relative to the coalescence baseline, enhancements of the yield ratios are observed in the 0%-10% most central collisions at 19.6 and 27 GeV with a significance of 2.3$\sigma$ and 3.4$\sigma$, respectively, with a combined significance of 4.1$\sigma$. The measured significance of these enhancements decreases with smaller $p_{T}$ acceptance. The enhancements are not observed in peripheral collisions and model calculations without critical fluctuation. Important implications on the QCD phase structure and the production mechanism of light nuclei in heavy-ion collisions are discussed.