New Hypernuclei Measurements from STAR

Abstract

Hypernuclei are bound states of hyperons (Y) and nucleons (N). Measurements on their yields can help us investigate their production mechanisms. In particular, the ${}^5_{\Lambda}$He and $^{4}_{\Lambda}$H(e) are substantially tighter bound compared to the $^{3}_{\Lambda}$H. The large radius of the $^{3}_{\Lambda}$H leads to suppression in coalescence models, but not in the thermal model where the size of the nucleus does not play a role. As such, studying the $A=3$--5 hypernuclei yields allow us to extract information on the effects of hypernuclear binding on hypernuclei production in heavy-ion collisions. In these proceedings, we present measurements of ${}^5_{\Lambda}$He yields in Au+Au collisions at $\sqrt{s_{\rm NN}}=3.0$ GeV, $^{4}_{\Lambda}$H(e) yields in Au+Au collisions at $\sqrt{s_{\rm NN}}=3.0$--$4.5$ GeV, and $^{3}_{\Lambda}$H yields in Au+Au collisions at $\sqrt{s_{\rm NN}}=3$--$27$ GeV. Results on the directed flow of hypernuclei are also reported. The physics implications of these measurements are discussed.