Speaker
Description
Despite extensive measurements on the production yields of light nuclei in heavy-ion collisions, a consensus on their formation mechanism remains elusive. In contrast to normal nuclei, hypernuclei carries strangeness and can offer an additional dimension for such studies. In particular, the hypertriton ${}^{3}_{\Lambda}{\rm H}$, a bound state consisting of a proton, neutron and $\Lambda$ hyperon, is the lightest known hypernucleus with a very small binding energy of $\sim 130$ keV. Currently, published measurements of the ${}^{3}_{\Lambda}{\rm H}$ yield are scarce and are limited to low ($\sqrt{s_{_\mathrm{NN}}}<5$ GeV) or high collision energies ($\sqrt{s_{_\mathrm{NN}}}\geq 200$ GeV). Precise measurements on the energy dependence of ${}^{3}_{\Lambda}{\rm H}$ production will give invaluable information on hypernuclei production mechanisms due to its unique intrinsic properties.
In this presentation, we will present comprehensive measurements of the collision energy dependence of ${}^{3}_{\Lambda}{\rm H}$ transverse momentum $p_{\rm T}$ and $p_{\rm T}$ -integrated yield at mid-rapidity in Au+Au collisions at ten collision energies between $\sqrt{s_{_\mathrm{NN}}}=$ 3 and 27 GeV. It is found that thermal model calculations overestimated the ${}^{3}_{\Lambda}{\rm H}$ yield and the ${}^{3}_{\Lambda}{\rm H}/\Lambda$ ratio by a factor of $\sim 2$ in the reported energy region, while coalescence calculations are closer to data. We will also present the mean $p_{\rm T}$ of ${}^{3}_{\Lambda}{\rm H}$ as a function of collision energy. The mean $p_{\rm T}$ of ${}^{3}_{\Lambda}{\rm H}$ is observed to be lower than the Blast-Wave expectation using the same freeze-out parameters from light hadrons. These observations suggest that similar to light nuclei, hypertritons are formed at a later stage than light hadrons possibly through nucleon/hyperon coalescence during these collisions.
