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Register a new userUpdated measurement of time-dependent $CP$-violating observables in $B^{0}_{s}to J/psi K^+ K^-$ decays
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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.
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We report a measurement of $CP$ violating asymmetries in $B^0(overline{B}^0) to K^+ K^- K^0_S$ decays with a time-dependent Dalitz approach. This analysis is based on a data sample of $657times 10^6$ $Boverline{B}$ pairs accumulated at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. As the result of an unbinned maximum likelihood fit to the selected candidates, the mixing-induced and direct $CP$ violation parameters, $phi^{rm eff}_1$ and ${cal A}_{CP}$ are obtained for $B^0 to phi(1020) K^0_S$, $B^0 to f_0(980) K^0_S$ and other $B^0 to K^+ K^- K^0_S$ decays. We find four solutions that describe the data. There are {eqnarray*} phi_1^{rm eff}(B^0to phi(1020) K^0_S) & = & (32.2 pm 9.0 pm 2.6 pm 1.4)^{circ}; phi_1^{rm eff}(B^0to phi(1020) K^0_S) & = & (26.2 pm 8.8 pm 2.7 pm 1.2)^{circ}; phi_1^{rm eff}(B^0to phi(1020) K^0_S) & = & (27.3 pm 8.6 pm 2.8 pm 1.3)^{circ}; {rm and} phi_1^{rm eff}(B^0to phi(1020) K^0_S) & = & (24.3 pm 8.0 pm 2.9 pm 5.2)^{circ}.{eqnarray*} The values for the $CP$ violating phase in $B^0to phi(1020) K^0_S$ are similar but other properties of the Dalitz plot are quite different for the four solutions. These four solutions have consistent $phi^{rm eff}_1$ values for all three $B$ meson decay channels and none of them deviates significantly from the values measured in $B to (cbar{c}) K^0$ decays with the currently available statistics. In addition, we find no significant direct $CP$ violation.
Measurements are presented of the $CP$ violation observables $S$ and $C$ in the decays of $B^0$ and $overline{B}{}^0$ mesons to the $J/psi K^0_S$ final state. The data sample corresponds to an integrated luminosity of $3.0,text{fb}^{-1}$ collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of $7$ and $8,text{TeV}$. The analysis of the time evolution of $41500$ $B^0$ and $overline{B}{}^0$ decays yields $S = 0.731 pm 0.035 , text{(stat)} pm 0.020 ,text{(syst)}$ and $C = -0.038 pm 0.032 , text{(stat)} pm 0.005,text{(syst)}$. In the Standard Model, $S$ equals $sin(2beta)$ to a good level of precision. The values are consistent with the current world averages and with the Standard Model expectations.
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.
A measurement is presented of decay-time-dependent $CP$ violation in the decays $B^0rightarrow J/psi K^0_mathrm{S}$ and $B^0rightarrowpsi(2S) K^0_mathrm{S}$, where the $J/psi$ is reconstructed from two electrons and the $psi(2S)$ from two muons. The analysis uses a sample of $pp$ collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 $mathrm{fb}^{-1}$. The $CP$-violation observables are measured to be begin{equation*} begin{aligned} Cleft(B^0rightarrow J/psi K^0_mathrm{S}right)&=phantom{+},0.12,pm,0.07pm,0.02,, Sleft(B^0rightarrow J/psi K^0_mathrm{S}right)&=phantom{+},0.83,pm,0.08pm,0.01,, Cleft(B^0rightarrowpsi(2S) K^0_mathrm{S}right)&=-,0.05,pm,0.10pm,0.01,, Sleft(B^0rightarrowpsi(2S) K^0_mathrm{S}right)&=phantom{+},0.84,pm,0.10pm,0.01,, end{aligned} end{equation*} where $C$ describes $CP$ violation in the direct decay, and $S$ describes $CP$ violation in the interference between the amplitudes for the direct decay and for the decay after $B^0$-$overline{B}^0$ oscillation. The first uncertainties are statistical and the second are systematic. The two sets of results are compatible with the previous LHCb measurement using $B^0rightarrow J/psi K^0_mathrm{S}$ decays, where the $J/psi$ meson was reconstructed from two muons. The averages of all three sets of LHCb results are begin{equation*} begin{aligned} Cleft(B^0rightarrow[cbar{c}]K^0_mathrm{S}right)&=-0.017 pm 0.029,, Sleft(B^0rightarrow[cbar{c}]K^0_mathrm{S}right)&=phantom{+}0.760 pm 0.034,, end{aligned} end{equation*} under the assumption that higher-order contributions to the decay amplitudes are negligible. The uncertainties include statistical and systematic contributions.
We present the result of a search for charge asymmetry in B^+ -> J/psi K^+ decays. The CP-violating charge asymmetry is measured to be A_CP(B^+ -> J/psi K^+) = [-0.76 +/- 0.50 (stat) +/- 0.22 (syst)]%.
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