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Register a new userMeasurement of $B^{0}_{s}$ and $D^{-}_{s}$ meson lifetimes
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We report on a measurement of the flavor-specific $B^{0}_{s}$ 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^{0}_{s} rightarrow D^{(*)-}_{s} mu^{+} u_mu $ decays are partially reconstructed in the $K^{+}K^{-}pi^{-}mu^{+}$ final state. The $B^{0}_{s}$ and $D^{-}_{s}$ natural widths are determined using, as a reference, kinematically similar $B^{0} rightarrow D^{(*)-}mu^{+} u_mu$ decays reconstructed in the same final state. The resulting differences between widths of $B^{0}_{s}$ 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 $B^{0}_{s}$ lifetime, $tau^{rm fs}_{B^{0}_{s}} = 1.547 pm 0.013 (stat) pm 0.010 (syst) pm 0.004 (tau_{B})$ 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.
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The decay mode $B^{0}_{s} to D^{mp}_{s} K^{pm} $ allows for one of the theoretically cleanest measurements of the CKM angle $gamma$ through the study of time-dependent $ensuremath{CP}xspace$ violation. This paper reports a measurement of its branching fraction relative to the Cabibbo-favoured mode $B^{0}_{s} to D^{-}_{s} pi^{+}$ based on a data sample of 0.37 fb$^{-1}$ proton-proton collisions at $sqrt{s} = 7$ TeV collected in 2011 with the LHCb detector. In addition, the ratio of $ensuremath{mathrm{B}}xspace$ meson production fractions $ensuremath{f_s/f_d}$, determined from semileptonic decays, together with the known branching fraction of the control channel $B^{0} to D^{-} pi^{+}$, is used to perform an absolute measurement of the branching fractions: $B (B^0_s to D^-_s pi^+) ;= (2.95 pm 0.05 pm 0.17^{,+,0.18}_{,-,0.22}) times 10^{-3}$, $B (B^0_s to D^mp_s K^pm) = (1.90 pm 0.12 pm 0.13^{,+,0.12}_{,-,0.14}) times 10^{-4},$, where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to $f_s/f_d$.
Measurements of $b$-hadron lifetimes are reported using $pp$ collision data, corresponding to an integrated luminosity of 1.0fb$^{-1}$, collected by the LHCb detector at a centre-of-mass energy of $7$Tev. Using the exclusive decays $B^+to J/psi K^+$, $B^0to J/psi K^*(892)^0$, $B^0to J/psi K^0_{rm S}$, $Lambda_b^0to J/psi Lambda$ and $B^0_sto J/psi phi$ the average decay times in these modes are measured to be $tau_{B^+to J/psi K^+}$ = $1.637 pm$ 0.004 $pm$ 0.003 ps, $tau_{B^0to J/psi K^*(892)^0}$ = $1.524 pm$ 0.006 $pm$ 0.004 ps, $tau_{B^0to J/psi K^0_{rm S}}$ = $1.499 pm$ 0.013 $pm$ 0.005 ps, $tau_{Lambda_b^0to J/psi Lambda}$ = $1.415 pm$ 0.027 $pm$ 0.006 ps and $tau_{B^0_sto J/psi phi}$ = $1.480 pm$ 0.011 $pm$ 0.005 ps, where the first uncertainty is statistical and the second is systematic. These represent the most precise lifetime measurements in these decay modes. In addition, ratios of these lifetimes, and the ratio of the decay-width difference, $DeltaGamma_d$, to the average width, $Gamma_d$, in the $B^0$ system, $Delta Gamma_d/Gamma_d = -0.044 pm 0.025 pm 0.011$, are reported. All quantities are found to be consistent with Standard Model expectations.
A binned Dalitz plot analysis of the decays $B^0 to D K^{ast 0}$, with $D to K_{S}^{0} pi^{+} pi^{-}$ and $K_{S}^{0} K^{+} K^{-}$, is performed to measure the observables $x_pm$ and $y_pm$, which are related to the CKM angle $gamma$ and the hadronic parameters of the decays. The $D$ decay strong phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of the $D$ decay model. With a sample of proton-proton collision data, corresponding to an integrated luminosity of $3.0,rm{fb}^{-1}$, collected by the LHCb experiment, the values of the $CP$ violation parameters are found to be $x_+ = 0.05 pm 0.35 pm 0.02$, $x_-=-0.31pm 0.20 pm 0.04$, $y_+=-0.81pm 0.28pm 0.06$ and $y_-=0.31pm 0.21 pm 0.05$, where the first uncertainties are statistical and the second systematic. These observables correspond to values $gamma$ = $(71 pm 20)^circ$, $r_{B^0} = 0.56pm 0.17$ and $delta_{B^0} = (204,^{+21}_{-20})^circ$. The parameters $r_{B^0}$ and $delta_{B^0}$ are the magnitude ratio and strong phase difference between the suppressed and favoured $B^0$ decay amplitudes, and have been measured in a region of $pm 50$ MeV/$c^2$ around the $K^{ast}(892)^{0}$ mass and with the magnitude of the cosine of the $K^{ast}(892)^{0}$ helicity angle larger than 0.4.
The relative production rate of $B^{0}_{s}$ and $B^{0}$ mesons is determined with the hadronic decays $B^{0}_{s} rightarrow D^{-}_{s}pi^{+}$ and $B^0 rightarrow D^{-}K^{+}$. The measurement uses data corresponding to 1.0 fb$^{-1}$ of $pp$ collisions at a centre-of-mass energy of $sqrt{s}=7$ TeV recorded in the forward region with the LHCb experiment. The ratio of production rates, $f_{s}/f_{d}$, is measured to be $0.238 pm 0.004 pm 0.015 pm 0.021 $, where the first uncertainty is statistical, the second systematic, and the third theoretical. This is combined with a previous LHCb measurement to obtain $f_{s}/f_{d} = 0.256 pm 0.020$. The dependence of $f_{s}/f_{d}$ on the transverse momentum and pseudorapidity of the $B$ meson is determined using the decays $B^{0}_{s} rightarrow D^{-}_{s}pi^{+}$ and $B^{0} rightarrow D^{-}pi^{+}$. There is evidence for a decrease with increasing transverse momentum, whereas the ratio remains constant as a function of pseudorapidity. In addition, the ratio of branching fractions of the decays $B^{0} rightarrow D^{-}K^{+}$ and $B^{0} rightarrow D^{-}pi^{+}$ is measured to be $0.0822 pm 0.0011 (textrm{stat}) pm 0.0025 (textrm{syst})$.
Using 6.32 fb$^{-1}$ of $e^+e^-$ collision data collected by the BESIII detector at the center-of-mass energies between 4.178 and 4.226 GeV,~an amplitude analysis of the $D^{+}_{s}rightarrow K^{0}_{S}K^{-}pi^{+}pi^{+}$ decays is performed for the first time to determine the intermediate-resonant contributions. The dominant component is the $D_s^+ to K^*(892)^+overline{K}^*(892)^0$ decay with a fraction of $(40.6pm2.9_{rm stat}pm4.9_{rm sys})$%. Our results of the amplitude analysis are used to obtain a more precise measurement of the branching fraction of the $D^{+}_{s}rightarrow K^{0}_{S}K^{-}pi^{+}pi^{+}$ decay, which is determined to be $(1.46pm0.05_{rm stat}pm0.05_{rm sys}$)%.
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