Observation of Directed Flow of Hypernuclei $_{\mathrm{\ensuremath{\Lambda}}}^{3}\mathrm{H}$ and $_{\mathrm{\ensuremath{\Lambda}}}^{4}\mathrm{H}$ in $\sqrt{{s}_{\mathrm{NN}}}=3\text{ }\text{ }\mathrm{GeV}$ $\mathrm{Au}+\mathrm{Au}$ Collisions at RHIC

Observation of Directed Flow of Hypernuclei ${}_{Λ}^{3}H$ and ${}_{Λ}^{4}H$ in $\sqrt{s_{NN}} = 3 GeV$ $Au + Au$ Collisions at RHIC

B. E. Aboona et al. (STAR Collaboration)

Phys. Rev. Lett. 130, 212301 – Published 24 May 2023

Abstract

We report here the first observation of directed flow ( $v_{1}$ ) of the hypernuclei ${}_{Λ}^{3}H$ and ${}_{Λ}^{4}H$ in mid-central $Au + Au$ collisions at $\sqrt{s_{NN}} = 3 GeV$ at RHIC. These data are taken as part of the beam energy scan program carried out by the STAR experiment. From $165 \times 10^{6}$ events in 5%–40% centrality, about 8400 ${}_{Λ}^{3}H$ and 5200 ${}_{Λ}^{4}H$ candidates are reconstructed through two- and three-body decay channels. We observe that these hypernuclei exhibit significant directed flow. Comparing to that of light nuclei, it is found that the midrapidity $v_{1}$ slopes of ${}_{Λ}^{3}H$ and ${}_{Λ}^{4}H$ follow baryon number scaling, implying that the coalescence is the dominant mechanism for these hypernuclei production in the 3 GeV $Au + Au$ collisions.