The production of the hypertriton nuclei $^{ 3}_{ \Lambda}\mathrm H$ and $^{ 3}_{ \bar{ \Lambda}} \overline{ \mathrm H}$ has been measured for the first time in Pb-Pb collisions at $\sqrt{ s_{ \rm NN}}$ = 2.76 TeV with the ALICE experiment at LHC energies. The total yield, d$N$/d$y$ $\times \mathrm{ B.R.}_{ \left( ^{ 3}_{ \Lambda}\mathrm H \rightarrow ^{ 3}\mathrm{ He},\pi^{ -} \right)} = \left( 3.86 \pm 0.77 (\mathrm{ stat.}) \pm 0.68 (\mathrm{ syst.})\right) \times 10^{ -5}$ in the 0-10% most central collisions, is consistent with the predictions from a statistical thermal model using the same temperature as for the light hadrons. The coalescence parameter $B_3$ shows a dependence on the transverse momentum, similar to the $B_2$ of deuterons and the $B_3$ of $^{ 3}\mathrm{ He}$ nuclei. The ratio of yields $S_3$ = $^{ 3}_{ \Lambda}\mathrm H$/($^{ 3}\mathrm{ He}$ $\times \Lambda/\mathrm{ p}$) was measured to be $S_3$ = 0.60 $\pm$ 0.13 (stat.) $\pm$ 0.21 (syst.) in 0-10% centrality events; this value is compared to different theoretical models. The measured $S_3$ is fully compatible with thermal model predictions. The measured $^{ 3}_{ \Lambda}\mathrm H$ lifetime, $ \tau = 181^{ +54}_{ -39} (\mathrm{ stat.}) \pm 33 (\mathrm{ syst.})\ \mathrm{ ps}$ is compatible within 1$\sigma$ with the world average value.
Categories: nucl-ex