Probing (Hyper)Nuclei Wave Functions and Production Mechanisms in $\sqrt{s_{\rm{NN}}}=200$ GeV Isobar Collisions at RHIC

Abstract

The study of nuclei and hypernuclei production is a powerful tool to investigate the formation mechanism of loosely bound states in high-energy heavy-ion collisions. A key prediction from coalescence models is a strong suppression of the hypertriton (${}^{3}_Λ\rm{H}$) compared to ${}^{3}\rm{He}$ production in small collision systems due to the larger radius of ${}^{3}_Λ\rm{H}$. In this letter, the STAR collaboration reports measurements on (hyper)nuclei ($^{3}_Λ\rm{H}, {}^{3}_{\barΛ}\rm{\bar{H}}, {}^{3}\rm{He}, {}^{3}\rm{\overline{He}}, t$) production at mid-rapidity in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\rm{NN}}}=200$ GeV as a function of collision centrality. We find that the ratios $N_{t}N_{p}/N_{d}^{2}$ and $S_{3} =(N_{{}^{3}_Λ\rm{H}}/N_{{}^{3}_{}\rm{He}})/(N_Λ/N_{p})$ deviate significantly from thermal model expectations. Coalescence calculations incorporating realistic non-Gaussian wave functions for the $d$ and ${}^{3}_Λ\rm{H}$ provide an improved description of the data, while Gaussian descriptions of the ${}^{3}_Λ\rm{H}$ wave function fail to simultaneously reproduce the measured $S_{3}$ and the binding energy of ${}^{3}_Λ\rm{H}$. These results suggest that the ${}^{3}_Λ\rm{H}$ wave function contains larger short-distance $d$--$Λ$ probability than implied by a Gaussian ansatz, demonstrating the potential of heavy-ion production measurements as a probe of hypernuclear wave functions and the underlying hyperon--nucleon interaction.