Measurement of the Λ hyperon lifetime

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