Measurement of the $\Lambda$ hyperon lifetime

Abstract

A new, more precise measurement of the $\Lambda$ hyperon lifetime is performed using a large data sample of Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with ALICE. The $\Lambda$ and $\overline{\Lambda }$ hyperons are reconstructed at midrapidity using their two-body weak decay channel $\Lambda \to \mathrm{p}+{\pi }^{-}$ and $\overline{\Lambda }\to \overline{\mathrm{p}}+{\pi }^{+}$. The measured value of the $\Lambda$ lifetime is ${\tau }_{\Lambda }=[261.07\pm 0.37(stat.)\pm 0.72(syst.)]\mathrm{ps}$. 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 $({\tau }_{\Lambda }-{\tau }_{\overline{\Lambda }})/{\tau }_{\Lambda }=0.0013\pm 0.0028(stat.)\pm 0.0021(syst.)$ 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.

20 pages, 5 captioned figures, 4 tables, authors from page 15, published version, figures at http://alice-publications.web.cern.ch/node/9097