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Register a new userMeasurement of the time-dependent CP asymmetries in $B_s^0rightarrow J/psi K_{rm S}^0$
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The first measurement of decay-time-dependent CP asymmetries in the decay $B_s^0rightarrow J/psi K_{rm S}^0$ and an updated measurement of the ratio of branching fractions $mathcal{B}(B_s^0rightarrow J/psi K_{rm S}^0)/mathcal{B}(B_d^0rightarrow J/psi K_{rm S}^0)$} are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fb$^{-1}$ of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The results on the CP asymmetries are $A_{DeltaGamma}(B_s^0rightarrow J/psi K_{rm S}^0) = 0.49_{-0.65}^{+0.77}(stat) pm 0.06(syst)$, $C_{rm dir}(B_s^0rightarrow J/psi K_{rm S}^0) = -0.28 pm 0.41(stat) pm 0.08(syst)$ and $S_{rm mix}(B_s^0rightarrow J/psi K_{rm S}^0) = -0.08 pm 0.40(stat) pm 0.08(syst)$. The ratio $mathcal{B}(B_s^0rightarrow J/psi K_{rm S}^0)/mathcal{B}(B_d^0rightarrow J/psi K_{rm S}^0)$ is measured to be $0.0431 pm 0.0017(stat) pm 0.0012(syst) pm 0.0025(f_s/f_d)$, where the last uncertainty is due to the knowledge of the $B_s^0$ and $B_d^0$ production fractions.
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Decays of the form $B^{0}_{(s)}rightarrow J/psi K_{{rm S}}^{0} h^+ h^{left(primeright) -}$ ($h^{(prime)} = K, pi$) are searched for in proton-proton collision data corresponding to an integrated luminosity of $1.0 , {rm fb}^{-1}$ recorded with the LHCb detector. The first observation of the $B^{0}_{s}rightarrow J/psi K_{{rm S}}^{0} K^{pm} pi^{mp}$ decay is reported, with significance in excess of 10 standard deviations. The $B^{0}rightarrow J/psi K_{{rm S}}^{0} K^{+} K^{-}$ decay is also observed for the first time. The branching fraction of $B^{0}rightarrow J/psi K_{{rm S}}^{0} pi^{+} pi^{-}$ is determined, to significantly better precision than previous measurements, using $B^0 rightarrow J/psi K_{{rm S}}^{0}$ as a normalisation channel. Branching fractions and upper limits of the other $B^{0}_{(s)}rightarrow J/psi K_{{rm S}}^{0} h^+ h^{left(primeright) -}$ modes are determined relative to that of the $B^{0}rightarrow J/psi K_{{rm S}}^{0} pi^{+} pi^{-}$ decay.
The decay-time-dependent $CP$ asymmetry in $B^{0}_{s}to J/psi K^{+} K^{-}$ decays is measured using proton-proton collision data, corresponding to an integrated luminosity of $1.9,mathrm{fb^{-1}}$, collected with the LHCb detector at a centre-of-mass energy of $13,mathrm{TeV}$ in 2015 and 2016. Using a sample of approximately 117,000 signal decays with an invariant $K^{+} K^{-}$ mass in the vicinity of the $phi(1020)$ resonance, the $CP$-violating phase $phi_s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the $B^{0}_{s}$-$bar{B}^{0}_{s}$ system, $DeltaGamma_s$. The difference of the average $B^{0}_{s}$ and $B^{0}$ meson decay widths, $Gamma_s-Gamma_d$, is determined using in addition a sample of $B^{0} to J/psi K^{+} pi^{-}$ decays. The values obtained are $phi_s = -0.083pm0.041pm0.006,mathrm{rad}$, $DeltaGamma_s = 0.077 pm 0.008 pm 0.003, mathrm{ps^{-1}}$ and $Gamma_s-Gamma_d = -0.0041 pm 0.0024 pm 0.0015,mathrm{ps^{-1}}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of these quantities to date and are consistent with expectations based on the Standard Model and with a previous LHCb analysis of this decay using data recorded at centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with recent results from $B^{0}_{s}to J/psi pi^{+} pi^{-}$ decays obtained using the same dataset as this analysis, and with previous independent LHCb results.
The time-dependent $CP$ asymmetry in $B_s^0 to J/psi K^+K^-$ decays is measured using $pp$ collision data, corresponding to an integrated luminosity of $3.0$fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of $7$ and $8$TeV. In a sample of 96 000 $B_s^0 to J/psi K^+K^-$ decays, the $CP$-violating phase $phi_s$ is measured, as well as the decay widths $Gamma_{L}$ and $Gamma_{H}$ of the light and heavy mass eigenstates of the $B_s^0-bar{B}_s^0$ system. The values obtained are $phi_s = -0.058 pm 0.049 pm 0.006$ rad, $Gamma_s equiv (Gamma_{L}+Gamma_{H})/2 = 0.6603 pm 0.0027 pm 0.0015$ps$^{-1}$, and$DeltaGamma_s equiv Gamma_{L} - Gamma_{H} = 0.0805 pm 0.0091 pm 0.0032$ps$^{-1}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of those quantities to date. A combined analysis with $B_s^{0} to J/psi pi^+pi^-$ decays gives $phi_s = -0.010 pm 0.039 $rad. All measurements are in agreement with the Standard Model predictions. For the first time the phase $phi_s$ is measured independently for each polarisation state of the $K^+K^- $ system and shows no evidence for polarisation dependence.
This paper reports the first measurement of the effective B_s^0 -> J/{psi} K_S^0 lifetime and an updated measurement of its time-integrated branching fraction. Both measurements are performed with a data sample, corresponding to an integrated luminosity of 1.0 fb^{-1} of pp collisions, recorded by the LHCb experiment in 2011 at a centre-of-mass energy of 7 TeV. The results are: tau_J/{psi}K_S^0 = 1.75 +/- 0.12 (stat) +/- 0.07 (syst) and BR(B_s^0 -> J/{psi} K_S^0) = (1.97 +/- 0.23) X 10^{-5}. For the latter measurement, the uncertainty includes both statistical and systematic sources.
The CP-violating asymmetry a_{sl}^s is studied using semileptonic decays of Bs and anti-Bs mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0/fb. The reconstructed final states are Ds^(+/-)mu ^(-/+), with the Ds^(+/-) particle decaying in the phipi^(+/-) mode. The Ds^(+/-)mu ^{-/+) yields are summed over Bs and anti-Bs initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain $a_{sl}^s$ = (-0.06 +/- 0.50 +/- 0.36)%, where the first uncertainty is statistical and the second systematic.
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