Revisiting the hypertriton lifetime puzzle

Conflicting values of the hypertriton (_Λ³H) lifetime were extracted in recent relativistic heavy-ion collision experiments. The ALICE Collaboration's reported _Λ³H lifetime τ(_Λ³H) is compatible within measurement uncertainties with the free Λ lifetime τ_Λ, as naively expected for a loosely bound Λ hyperon in _Λ³H, whereas STAR's reported range of τ(_Λ³H) values is considerably shorter: τ_STAR(_Λ³H)∼(0.4-0.7)τ_Λ. This _Λ³H lifetime puzzle is revisited theoretically, using _Λ³H three-body wavefunctions generated in a chiral effective field theory approach to calculate the decay rate Γ(_Λ³H→³He+π⁻). Significant but opposing contributions arise from ΣNN admixtures in _Λ³H and from π⁻-³He final-state interaction. Evaluating the inclusive π⁻ decay rate Γ_π⁻(_Λ³H) via a branching ratio Γ(_Λ³H→³He+π⁻)/Γ_π⁻(_Λ³H) determined in helium bubble-chamber experiments, and adding Γ_π⁰(_Λ³H) through the [Formula presented] rule, we derive τ(_Λ³H) assuming several different values of the Λ separation energy B_Λ(_Λ³H). It is concluded that each of ALICE and STAR reported τ(_Λ³H) intervals implies its own constraint on B_Λ(_Λ³H): B_Λ≲0.1 MeV for ALICE, B_Λ≳0.2 MeV for STAR.