Measurement of the $_{\Lambda}^{3}H$ lifetime in Au+Au collisions at the BNL Relativistic Heavy Ion Collider

Abstract

A precise measurement of the hypertriton lifetime is presented. In this letter, the mesonic decay modes Λ3H→3He+π− and Λ3H→d+p+π− are used to reconstruct the hypertriton from Au+Au collision data collected by the STAR collaboration at RHIC. A minimum χ2 estimation is used to determine the lifetime of τ=142−21+24(stat.)±31(syst.) ps. This lifetime is about 50% shorter than the lifetime τ=263±2 ps of a free Λ, indicating strong hyperon-nucleon interaction in the hypernucleus system. The branching ratios of the mesonic decay channels are also determined to satisfy B.R.(3He+π−)//(3He+π−)+(d+p+π−))) = 0.32±0.05(stat.)±0.08(syst.). Our ratio result favors the assignment J(Λ3H) = 12 over J(Λ3H) = 32. These measurements will help to constrain models of hyperon-baryon interactions.