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Register a new userMeasurements of the $B^+$, $B^0$, $B_s^0$ meson and $Lambda_b^0$ baryon lifetimes
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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.
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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.
We perform a quantitative analysis of the $bbbar{b}bar{b}$ tetraquark decays into hidden- and open-bottom mesons and calculate, for the first time, the $bbbar{b}bar{b}$ tetraquark total decay width. On the basis of our results, we propose the $bbbar{b}bar{b} to B^{+} B^{-} (B^0 bar{B}^0) (B_s^0 bar{B}_s^0) to l^{+} l^{-}+text{X}$ decays as the most suitable channels to observe the $bbbar{b}bar{b}$ tetraquark states, since the calculated two-lepton cross section upper limit, $simeq 39 $ fb, is so large as to be potentially detectable with the 2018 LHCb sensitivity, paving the way to the observation of the $bbbar{b}bar{b}$ tetraquark in the future LHCb upgrade. The $4mu$ signal for the ground state, $J^{PC}=0^{++}$, is likely to be too small even for the upgraded LHCb, but it may not be hopeless for the $J^{PC}=2^{++}$ fully-bottom state.
The $CP$ asymmetry in the mixing of $B_s^0$ and $overline{B}{}_s^0$ mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Semileptonic $B_s^0$ and $overline{B}{}_s^0$ decays are studied in the inclusive mode $D_s^{mp} mu^{pm} u_{mu} X$ with the $D_s^{mp}$ mesons reconstructed in the $K^+ K^- pi^{mp}$ final state. Correcting the observed charge asymmetry for detection and background effects, the $CP$ asymmetry is found to be $a_{text{sl}}^s = (0.39 pm 0.26 pm 0.20) % $, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of $a_{text{sl}}^s$ to date. It is consistent with the prediction from the Standard Model and will constrain new models of particle physics.
The first observation of the $B_s^0 to overline{D}^{*0} phi$ decay is reported, with a significance of more than seven standard deviations, from an analysis of $pp$ collision data corresponding to an integrated luminosity of 3 fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of $7$ and $8$ TeV. The branching fraction is measured relative to that of the topologically similar decay $B^0 to overline{D}^0 pi^+pi^-$ and is found to be $mathcal{B}(B_s^0 to overline{D}^{*0} phi) = (3.7 pm 0.5 pm 0.3 pm 0.2) times 10^{-5}$, where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the $B^0 to overline{D}^0 pi^+pi^-$ decay. The fraction of longitudinal polarisation in this decay is measured to be ${f_{rm L} =(73 pm 15 pm 3)%}$. The most precise determination of the branching fraction for the $B_s^0 to overline{D}^{0} phi$ decay is also obtained, $mathcal{B}(B_s^0 to overline{D}^{0} phi) = (3.0 pm 0.3 pm 0.2 pm 0.2) times 10^{-5}$. An upper limit, $mathcal{B}(B^0 to overline{D}^{0} phi) < 2.0 (2.2) times 10^{-6}$ at $90%$ (95%) confidence level is set. A constraint on the $omega-phi$ mixing angle $delta$ is set at $|delta| < 5.2^circ~ (5.5^circ)$ at $90%$ ($95%$) confidence level.
The $B^0$--$bar B^0$ oscillation frequency $Delta m_d$ is measured by the LHCb experiment using a dataset corresponding to an integrated luminosity of $1.0,$fb$^{-1}$ of proton-proton collisions at $sqrt{s} = 7,$TeV, and is found to be $Delta m_d = 0.5156 pm 0.0051,($stat.$) pm 0.0033,($syst.$),$ps$^{-1}$. The measurement is based on results from analyses of the decays $B^0 to D^- pi^+$ ($D^- to K^+ pi^- pi^-$) and $B^0 to J/ psi K^{*0}$ ($ J/ psi to mu^+ mu^-$, $K^{*0} to K^+ pi^-$) and their charge conjugated modes.
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