Measurement of the Λ hyperon lifetime

Abstract

A new, more precise measurement of the Λ hyperon lifetime is performed using a large data sample of Pb–Pb collisions at √ˢɴɴ = 5.02 TeV with ALICE. The Λ and Λ̄ hyperons are reconstructed at midrapidity using their two-body weak decay channel Λ → p + π⁻ and Λ̄ → p̄ + π⁺. The measured value of the Λ lifetime is τΛ = [261.07 ± 0.37 (stat.) ± 0.72 (syst.)] ps. The relative difference between the lifetime of Λ and Λ̄, which represents an important test of CPT invariance in the strangeness sector, is also measured. The obtained value (τΛ − τΛ̄)/τΛ = 0.0013 ± 0.0028 (stat.) ± 0.0021 (syst.) is consistent with zero within the uncertainties. Both measurements of the Λ hyperon lifetime and of the relative difference between τΛ and τΛ̄ are in agreement with the corresponding world averages of the Particle Data Group and about a factor of three more precise.