Collision Energy Dependence of Hypertriton Production in Au+Au Collisions at RHIC

The STAR Collaboration reports measurements of the collision energy dependence of hypertriton (${}_{\mathrm{\Lambda }}^3$H) transverse momentum spectra and $p_{\mathrm{T}}$-integrated yields at mid-rapidity ($\mathrm{\mid }y\mathrm{\mid }<$0.5) in Au+Au collisions at 11 collision energies between 3.2 and 27,GeV. The measured ${}_{\mathrm{\Lambda }}^3$H yields and ${}_{\mathrm{\Lambda }}^3$H/$\mathrm{\Lambda }$ yields ratio in central collisions increase strongly with decreasing collision energy, and are a factor of $\sim$2 lower than thermal model predictions at this energy range. The mean $p_{\mathrm{T}}$ of ${}_{\mathrm{\Lambda }}^3$H is lower than the Blast-Wave expectation using the freeze-out parameters from light hadrons. Furthermore, the observed double ratio $({}_{\mathrm{\Lambda }}^3\mathrm{H}\mathrm{/}\mathrm{\Lambda })\mathrm{/}(t\mathrm{/}p)$ maintains a constant value of $\sim$0.4 across the measured energy range. Within the coalescence framework, this ratio directly reflects the significantly suppressed formation probability of the weakly-bound hypertriton relative to the triton, which results from the weaker hyperon-nucleon interaction compared with the nucleon-nucleon interaction.