Softening of the Hypertriton Transverse Momentum Spectrum in Heavy-Ion Collisions

Understanding the properties of hypernuclei helps to constrain the interaction between hyperon and nucleon, which is known to play an essential role in determining the properties of neutron stars. Experimental measurements have suggested that the hypertriton (HΛ3), the lightest hypernucleus, exhibits a halo structure with a deuteron core encircled by a Λ hyperon at a distance of about 10 fm. This large Λ−d distance in HΛ3 wave function is found to cause a suppressed HΛ3 yield and a softening of its transverse momentum (pT) spectrum in relativistic heavy-ion collisions. Within the coalescence model based on nucleons and Λ hyperons from a microscopic hybrid hydro model with a hadronic afterburner for nuclear cluster production in Pb-Pb collisions at sNN= 5.02 TeV, we show how this softening of the hypertriton pT spectrum appears and leads to a smaller mean pT for HΛ3 than for helium-3 (3He). The latter is opposite to the predictions from the blast-wave model which assumes that HΛ3 and 3He are thermally produced at the kinetic freeze-out of heavy-ion collisions. The discovered quantum mechanical softening of the (anti-)hypertriton spectrum can be experimentally tested in relativistic heavy-ion collisions at different collision energies and centralities and used to obtain valuable insights to the mechanisms for light (hyper-)nuclei production in these collisions.