Measurement of hyper triton lifetime in Au + Au collisions at the Relativistic Heavy-Ion Collider

A precise measurement of the hypertriton lifetime is presented. In this letter, the mesonic decay modes $\mathrm{{^3_\Lambda}H \rightarrow ^3He + \pi^-}$and$${}_{\mathrm{\Lambda }}^3\mathrm{H}\to \mathrm{d}+\mathrm{p}+{\pi }^{-}$$ are used to reconstruct the hypertriton from Au+Au collision data collected by the STAR collaboration at RHIC. A minimum ${\chi }^2$ estimation is used to determine the lifetime of $\tau =142_{-21}^{+24}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{.})\pm 31(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{.})$ ps. This lifetime is about 50% shorter than the lifetime $\tau =263\pm 2$ ps of a free $\mathrm{\Lambda }$, indicating strong hyperon-nucleon interaction in the hypernucleus system. The branching ratios of the mesonic decay channels are also determined to satisfy B.R.${}_{{(}^3\mathrm{H}\mathrm{e}+{\pi }^{-})}\mathrm{/}$(B.R.${(^3{\rm He}+\pi^-)}+$B\mathrm{.}R\mathrm{.}${(d+p+\pi^-)})$=$0.32\rm{\pm}0.05,{\rm (stat.)}\pm 0.08,{\rm (syst.)}$\mathrm{.}Ourratioresultfavorstheassignment$J(${}_{\mathrm{\Lambda }}^3\mathrm{H}$)$=$\frac{1}{2}$over$J(${}_{\mathrm{\Lambda }}^3\mathrm{H}$)$=$\frac{3}{2}$. These measurements will help to constrain models of hyperon-baryon interactions.