Hyper-Nuclei ${}_{\mathrm{\Lambda }}^4\text{He}$ Production in $\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 3 GeV Au+Au collisions at RHIC

The STAR experiment reports the first measurement of the ${}_{\mathrm{\Lambda }}^4\text{He}$ hyper-nuclei yield as a function of rapidity and transverse momentum in 0-50% central Au+Au collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=$ 3 GeV. The ${}_{\mathrm{\Lambda }}^4\text{He}$ is reconstructed through its three-body decay channel, ${}_{\mathrm{\Lambda }}^4\mathrm{H}\mathrm{e}\to {}^3\mathrm{H}\mathrm{e}+\mathrm{p}+{\pi }^{-}$, with a statistical significance of about 9.5 standard deviations. We find that the yield of ${}_{\mathrm{\Lambda }}^4\text{He}$ as a function of rapidity is consistent with that of ${}_{\mathrm{\Lambda }}^4\text{H}$, and the rapidity-dependent yield ratio of ${}_{\mathrm{\Lambda }}^4\text{He}$/${}_{\mathrm{\Lambda }}^4\text{H}$ is consistent with that of ${}^3$He/t. All the measurements, as well as the transverse-momentum spectra, can be reasonably described by the JAM with a coalescence afterburner, suggesting a coalescence-based formation scenario for hyper-nuclei at this energy. The canonical thermal model reproduces the observed yield ratios but overpredicts the absolute hyper-nuclei yields.