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

Abstract

The STAR experiment reports the first measurement of the ${}_{\Lambda }^{4}He$ hyper-nuclei yield as a function of rapidity and transverse momentum in 0-50% central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 3 GeV. The ${}_{\Lambda }^{4}He$ is reconstructed through its three-body decay channel, ${}_{\Lambda }^4\mathrm{He}\to {}^3\mathrm{He}+\mathrm{p}+{\pi }^{-}$, with a statistical significance of about 9.5 standard deviations. We find that the yield of ${}_{\Lambda }^{4}He$ as a function of rapidity is consistent with that of ${}_{\Lambda }^{4}H$, and the rapidity-dependent yield ratio of ${}_{\Lambda }^{4}He$/${}_{\Lambda }^{4}H$ 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.

17 pages, 6 figures, 2 tables