Measurement of $B_s^0$ and $D_s^{-}$ meson lifetimes

Abstract

We report on a measurement of the flavor-specific $B_s^0$ lifetime and of the $D_s^{-}$ lifetime using proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to 3.0 fb${}^{-1}$ of integrated luminosity. Approximately 407 000 $B_s^0\to D_s^{(\ast )-}{\mu }^{+}{\nu }_{\mu }$ decays are partially reconstructed in the $K^{+}{K}^{-}{\pi }^{-}{\mu }^{+}$ final state. The $B_s^0$ and $D_s^{-}$ natural widths are determined using, as a reference, kinematically similar $B^0\to D^{(\ast )-}{\mu }^{+}{\nu }_{\mu }$ decays reconstructed in the same final state. The resulting differences between widths of $B_s^0$ and $B^0$ mesons and of $D_s^{-}$ and $D^{-}$ mesons are ${\Delta }_{\Gamma }(B)=-0.0115\pm 0.0053(stat)\pm 0.0041(syst)$ ps${}^{-1}$ and ${\Delta }_{\Gamma }(D)=1.0131\pm 0.0117(stat)\pm 0.0065(syst)$ ps${}^{-1}$, respectively. Combined with the known $B^0$ and $D^{-}$ lifetimes, these yield the flavor-specific $B_s^0$ lifetime, ${\tau }_{B_s^0}^{\mathrm{fs}}=1.547\pm 0.013(stat)\pm 0.010(syst)\pm 0.004({\tau }_B)$ ps and the $D_s^{-}$ lifetime, ${\tau }_{D_s^{-}}=0.5064\pm 0.0030(stat)\pm 0.0017(syst)\pm 0.0017({\tau }_D)$ ps The last uncertainties originate from the limited knowledge of the $B^0$ and $D^{-}$ lifetimes. The results improve upon current determinations.

16 pages, 8 figures. Minor editorial changes to match the published version. All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2017-004.html