Observation of Directed Flow of Hypernuclei H Λ3 and H Λ4 in sNN =3 GeV Au+Au Collisions at RHIC

Abstract

We report here the first observation of directed flow (v1) of the hypernuclei HΛ3 and HΛ4 in mid-central Au+Au collisions at sNN=3 GeV at RHIC. These data are taken as part of the beam energy scan program carried out by the STAR experiment. From 165×106 events in 5%-40% centrality, about 8400 HΛ3 and 5200 HΛ4 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 v1 slopes of HΛ3 and HΛ4 follow baryon number scaling, implying that the coalescence is the dominant mechanism for these hypernuclei production in the 3 GeV Au+Au collisions.