Measurement of the Λ hyperon lifetime

A new, more precise measurement of the Λ hyperon lifetime is performed using a large data sample of Pb–Pb collisions at √sNN =5.02  TeV with ALICE. The Λ and ¯Λ hyperons are reconstructed at midrapidity using their two-body weak decay channel Λ→p+π− and ¯Λ→¯p+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 ¯Λ, which represents an important test of CPT invariance in the strangeness sector, is also measured. The obtained value (τΛ−τ¯Λ)/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 τ¯Λ are in agreement with the corresponding world averages of the Particle Data Group and about a factor of three more precise.