Measurement of B_s^0 and D_s^- Meson Lifetimes

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→D_s^(*)-μ^+ν_μ decays are partially reconstructed in the K^+K^-π^-μ^+ final state. The B_s^0 and D_s^- natural widths are determined using, as a reference, kinematically similar B^0→D^(*)-μ^+ν_μ 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 Δ_Γ(B)=-0.0115±0.0053(stat)±0.0041(syst)  ps^-1 and Δ_Γ(D)=1.0131±0.0117(stat)±0.0065(syst)  ps^-1, respectively. Combined with the known B^0 and D^- lifetimes, these yield the flavor-specific B_s^0 lifetime, τ_B_s^0^fs=1.547±0.013(stat)±0.010(syst)±0.004(τ_B)  ps and the D_s^- lifetime, τ_D_s^-=0.5064±0.0030(stat)±0.0017(syst)±0.0017(τ_D)  ps. The last uncertainties originate from the limited knowledge of the B^0 and D^- lifetimes. The results improve upon current determinations.