Probing (Hyper)Nuclei Wave Functions and Production Mechanisms in $\sqrt{s_{\mathrm{NN}}}=200$ 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 (${}_{\Lambda }^3\mathrm{H}$) compared to ${}^3\mathrm{He}$ production in small collision systems due to the larger radius of ${}_{\Lambda }^3\mathrm{H}$. In this letter, the STAR collaboration reports measurements on (hyper)nuclei (${}_{\Lambda }^3\mathrm{H},{}_{\bar{\mathrm{\Lambda }}}^3\bar{\mathrm{H}},{}^3\mathrm{He},{}^3\overline{\mathrm{He}},\mathrm{t}$) production at mid-rapidity in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV as a function of collision centrality. We find that the ratios $N_t{N}_p/N_d^2$ and $S_3=(N_{{}_{\Lambda }^3\mathrm{H}}/N_{{}_{}^3\mathrm{He}})/(N_{\Lambda }/N_p)$ deviate significantly from thermal model expectations. Coalescence calculations incorporating realistic non-Gaussian wave functions for the $d$ and ${}_{\Lambda }^3\mathrm{H}$ provide an improved description of the data, while Gaussian descriptions of the ${}_{\Lambda }^3\mathrm{H}$ wave function fail to simultaneously reproduce the measured $S_3$ and the binding energy of ${}_{\Lambda }^3\mathrm{H}$. These results suggest that the ${}_{\Lambda }^3\mathrm{H}$ wave function contains larger short-distance $d$--$\Lambda$ 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.

Comments: Main: 7 pages, 3 figures; Supplemental Note: 5 pages, 3 figures