Revisiting the hypertriton lifetime puzzle

• Main Authors: A. Pérez-Obiol, D. Gazda, E. Friedman, A. Gal
• Format: Article
• Language: English
• Published: Elsevier 2020-12-01
• Series: Physics Letters B
• Subjects: Few-body Λ hypernuclei; Λ3H lifetime experiments and calculations; EFT hyperon-nucleon forces
• Online Access: http://www.sciencedirect.com/science/article/pii/S037026932030719X

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 τΛ, as naively expected for a loosely bound Λ hyperon in Λ3H, whereas STAR's reported range of τ(Λ3H) values is considerably shorter: τSTAR(Λ3H)∼(0.4-0.7)τΛ. 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 Γπ−(Λ3H) via a branching ratio Γ(Λ3H→3He+π−)/Γπ−(Λ3H) determined in helium bubble-chamber experiments, and adding Γπ0(Λ3H) through the ΔI=12 rule, we derive τ(Λ3H) assuming several different values of the Λ separation energy BΛ(Λ3H). It is concluded that each of ALICE and STAR reported τ(Λ3H) intervals implies its own constraint on BΛ(Λ3H): BΛ≲0.1 MeV for ALICE, BΛ≳0.2 MeV for STAR.