Precision measurement of the ${\Lambda }_c^{+}$, ${\Xi }_c^{+}$ and ${\Xi }_c^0$ baryon lifetimes

Abstract

We report measurements of the lifetimes of the ${\Lambda }_c^{+}$, ${\Xi }_c^{+}$ and ${\Xi }_c^0$ charm baryons using proton-proton collision data at center-of-mass energies of 7 and 8\tev, corresponding to an integrated luminosity of 3.0 fb${}^{-1}$, collected by the LHCb experiment. The charm baryons are reconstructed through the decays ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$, ${\Xi }_c^{+}\to p{K}^{-}{\pi }^{+}$ and ${\Xi }_c^0\to p{K}^{-}{K}^{-}{\pi }^{+}$, and originate from semimuonic decays of beauty baryons. The lifetimes are measured relative to that of the $D^{+}$ meson, and are determined to be \begin{align*} \tau_{\Lambda_c^+} &= 203.5\pm1.0\pm1.3\pm1.4~{\rm fs}, \newline \tau_{\Xi_c^+} &= 456.8\pm3.5\pm2.9\pm3.1~{\rm fs}, \newline \tau_{\Xi_c^0} &= 154.5\pm1.7\pm1.6\pm1.0~{\rm fs}, \end{align*} where the uncertainties are statistical, systematic, and due to the uncertainty in the $D^{+}$ lifetime. The measurements are approximately 3--4 times more precise than the current world average values. The ${\Lambda }_c^{+}$ and ${\Xi }_c^{+}$ lifetimes are in agreement with previous measurements; however, the ${\Xi }_c^0$ baryon lifetime is approximately 3.3 standard deviations larger than the world average value.

Comments: 9 pages, 2 figures. All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2019-008.html