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

• Received 7 April 2023
• Accepted 9 June 2023

DOI:https://doi.org/10.1103/PhysRevD.108.032009

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

© 2023 CERN, for the ALICE Collaboration