Revisiting the hypertriton lifetime puzzle

Abstract

Conflicting values of the hypertriton (${}_{\Lambda }^3$H) lifetime were extracted in recent relativistic heavy-ion collision experiments. The ALICE Collaboration's reported ${}_{\Lambda }^3$H lifetime $\tau {(}_{\Lambda }^3$H) is compatible within measurement uncertainties with the free $\Lambda$ lifetime ${\tau }_{\Lambda }$, as naively expected for a loosely bound $\Lambda$ hyperon in ${}_{\Lambda }^3$H, whereas STAR's reported range of $\tau {(}_{\Lambda }^3$H) values is considerably shorter: ${\tau }_{\mathrm{STAR}}{(}_{\Lambda }^3$H)$\sim$(0.4-0.7)${\tau }_{\Lambda }$. This ${}_{\Lambda }^3$H lifetime puzzle is revisited theoretically using ${}_{\Lambda }^3$H three-body wavefunctions generated in a chiral effective field theory approach to calculate the decay rate $\Gamma {(}_{\Lambda }^3$H${\to }^3$He$+{\pi }^{-}$). Significant but opposing contributions arise from $\Sigma NN$ admixtures in ${}_{\Lambda }^3$H and from ${\pi }^{-}$-${}^3$He final-state interaction. Evaluating the inclusive ${\pi }^{-}$ decay rate ${\Gamma }_{{\pi }^{-}}{(}_{\Lambda }^3$H) via a branching ratio $\Gamma {(}_{\Lambda }^3$H${\to }^3$He+${\pi }^{-})/{\Gamma }_{{\pi }^{-}}{(}_{\Lambda }^3$H) determined in helium bubble-chamber experiments, and adding ${\Gamma }_{{\pi }^0}{(}_{\Lambda }^3$H) through the $\Delta I=\frac{1}{2}$ rule, we derive $\tau {(}_{\Lambda }^3$H) assuming several different values of the $\Lambda$ separation energy $B_{\Lambda }{(}_{\Lambda }^3$H). It is concluded that each of ALICE and STAR reported $\tau {(}_{\Lambda }^3$H) intervals implies its own constraint on $B_{\Lambda }{(}_{\Lambda }^3$H): $B_{\Lambda }\lesssim 0.1$ MeV for ALICE, $B_{\Lambda }\gtrsim 0.2$ MeV for STAR.

arXiv comment14 pages, 3 tables, 1 figure. v1 -- before submission for publication. v2 -- minor editorial revisions, as submitted for publication. v3 -- slight editorial revision, few references deleted and few added. v4 -- PLB 811 (2020) 135916 published version

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Cited by in corpus (11)

• The ALICE experiment: a journey through QCD
• Measurements of ${}_{\Lambda }^3\mathrm{H}$ and ${}_{\Lambda }^4\mathrm{H}$ Lifetimes and Yields in Au+Au Collisions in the High Baryon Density Region
• Measurement of the lifetime and $\Lambda$ separation energy of ${}_{\Lambda }^3\mathrm{H}$
• Lifetime of the hypertriton
• Observation of the Antimatter Hypernucleus ${}_{\bar{\Lambda }}^4\overline{H}$
• Consequences of increased hypertriton binding for $s$-shell $\Lambda$-hypernuclear systems
• Binding energy of ${}_{\Lambda }^3\mathrm{H}$ and ${}_{\Lambda }^4\mathrm{H}$ via image analyses of nuclear emulsions using deep-learning
• Hypertriton lifetime
• Hypernuclei and Antihypernuclei Production in Heavy-Ion Collisions
• Lifetime of the hypertriton
• Recent progress on few-body hypernuclei