Investigating the hyperon-nucleon strong interaction with a precision measurement of the hypertriton lifetime in ALICE

Abstract

The hypertriton is a bound state of a proton, a neutron and a Λ baryon. Studying its internal structure is crucial to investigate the hyperon–nucleon strong interaction and offers insights into the inner core of neutron stars, where Λ production is favoured. One powerful way to investigate the hypertriton’s internal structure is to measure precisely its lifetime. The hypertriton is an extremely loosely bound object with a lambda separation energy EΛ of only 130 keV. Therefore the hypertriton lifetime is expected to be close to the one of the free Λ. Thanks to the very large set of Pb–Pb collision data collected during LHC Run 2, the ALICE collaboration has performed systematic studies on the hypertriton lifetime. The hypertriton 2-body mesonic decay channel has been studied with the help of machine learning techniques for the signal extraction. The precision of the new ALICE results on the hypertriton lifetime is comparable with the current world average and the measured lifetime value confirms the weakly-bound nature of the hypertriton.