The lifetime of heavy hypernuclei studied by the delayed fission – JLab E02-017

Abstract

Based on the combination of opening of non-mesonic decay channels and the short range nature of ΛN interaction, the lifetime of Λ hypernuclei was theoretically expected to be shorter than that of free Λ but saturated to a constant value (τ ≈ 200 ps) as hypernuclear mass increasing from light to heavy. While the lifetimes of light to medium-heavy hypernuclei were precisely measured by the KEK experiments suggesting observation of such a saturation, the results on heavy hypernuclei studied by the time delayed fission fragments at CERN and COSY were quite conflicting. The JLab experiment E02-017 applied a different method in studying the decay process of heavy hypernuclei via fissions induced by non-mesonic decay. The lifetimes of medium-heavy hypernuclei were measured directly from decay time spectra and the process of weak decay via delayed fission was better understood. Its result supports the prediction of a saturated lifetime as mass number (A) increases from p-shell and beyond.