Measurement of the $\Lambda$ hyperon lifetime

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