Measurement of the $B_s^0$ lifetime in the flavor-specific decay channel $B_s^0 \to D_s^- \mu^+\nu X$

Abstract

We present an updated measurement of the $B_s^0$ lifetime from the D0 collaboration using the semileptonic decays $B_s^0\rightarrow D_s^-\mu^+\nu X$, with $D_s^- \to \phi \pi^-$ and $\phi \to K^+K^-$ (and the charge conjugate process). This measurement uses the full Tevatron Run II sample of proton-antiproton collisions at $\sqrt{s} = 1.96$~TeV, comprising an integrated luminosity of 10.4~fb$^{-1}$. We find a flavor-specific lifetime $\tau_{\mathrm{fs}}(B_s^0)=1.479\pm0.010\thinspace{\rm(stat)}\pm0.021\thinspace{\rm(syst)}\thinspace\rm{ps}$. This technique is also used to determine the $B^0$ lifetime using the analogous $B^0\to D^-\mu^+\nu X$ decay with $D^-\to\phi\pi^-$, yielding $\tau(B^0)=1.534\pm0.019\thinspace{\rm(stat)}\pm0.021\thinspace{\rm(syst)}\thinspace\rm{ps}$. Both measurements are consistent with the current world averages, and the $B_s^0$ lifetime measurement is one of the most precise to date. Taking advantage of the cancellation of systematic uncertainties, we determine the lifetime ratio $\tau_{\mathrm{fs}}(B_s^0)/\tau(B^0) = 0.964\pm0.013\thinspace{\rm(stat)}\pm0.007\thinspace{\rm(syst)}$.