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arXiv · 2606.22457

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

The STAR Collaboration
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Abstract

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

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The STAR Collaboration. 2026-06-21. Hyper-Nuclei $^4_{\Lambda}\hbox{He}$ Production in $\sqrt{s_{\rm{NN}}}$ = 3 GeV Au+Au collisions at RHIC. https://arxiv.org/abs/2606.22457

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