Towards resolving the $_Λ^3$H lifetime puzzle

Abstract

Recent $_Λ^3$H lifetime measurements in relativistic heavy ion collision experiments have yielded values shorter by (30$\pm$8)% than the free $Λ$ lifetime $τ_Λ$, thereby questioning the naive expectation that $τ({_Λ^3}{\rm H})\approxτ_Λ$ for a weakly bound $Λ$ hyperon. Here we apply the closure approximation introduced by Dalitz and coworkers to evaluate the $_Λ^3$H lifetime, using $_Λ^3$H wavefunctions generated by solving three-body Faddeev equations. Our result, disregarding pion final-state interaction (FSI), is $τ({_Λ^3}{\rm H})$=(0.90$\pm$0.01)$τ_Λ$. In contrast to previous works, pion FSI is found attractive, reducing further $τ({_Λ^3}{\rm H})$ to $τ({_Λ^3}{\rm H})$=(0.81$\pm$0.02)$τ_Λ$. We also evaluate for the first time $τ({_Λ^3}{\rm n})$, finding it considerably longer than $τ_Λ$, contrary to the shorter lifetime values suggested by the GSI HypHI experiment for this controversial hypernucleus.

v2--14 pages, 1 figure, 2 tables, replaced title of v1 and recalculated a shorter $_Λ^3$H lifetime than reported in v1; v3--updated references, matching published version