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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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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)]%.
The $B^{pm}$ meson production asymmetry in $pp$ collisions is measured using $B^+ to bar{D}^0 pi^+$ decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at centre-of-mass energies of $sqrt{s}=$ 7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range $2 < p_{rm T} < 30$ GeV/$c$, and rapidities in the range $2.1 < y < 4.5$, are measured to be begin{align*} mathcal{A}_{rm prod}(B^+,sqrt{s}=7~{rm TeV}) &= (-0.41 pm 0.49 pm 0.10) times 10^{-2}, mathcal{A}_{rm prod}(B^+,sqrt{s}=8~{rm TeV}) &= (-0.53 pm 0.31 pm 0.10) times 10^{-2}, end{align*} where the first uncertainties are statistical and the second are systematic. These production asymmetries are used to correct the raw asymmetries of $B^{+} to J/psi K^{+}$ decays, thus allowing a measurement of the $CP$ asymmetry, begin{equation*} mathcal{A}_{CP} = (0.09 pm 0.27 pm 0.07) times 10^{-2}. end{equation*}
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.
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.
We report on the first measurement of the direct $CP$-violating asymmetry ($mathcal{A}$) in the charmless decay $B^0 to K^0pi^0$ at Belle II and an updated measurement of its branching fraction ($mathcal{B}$). We use a sample of electron-positron collisions collected in 2019 and 2020 at the $Upsilon(4S)$ resonance and corresponding to $62.8$ $text{fb}^{-1}$ of integrated luminosity. We reconstruct and select about $50$ $B^0 to K_S^0 pi^0$ candidates, and we measure $mathcal{A}_{{K^0pi^0}} = -0.40_{-0.44}^{+0.46} (text{stat}) pm 0.04 (text{syst})$ and $mathcal{B}(B^0 to K^0 pi^0) = [8.5_{-1.6}^{+1.7} (text{stat}) pm 1.2 (text{syst})] times 10^{-6}$. This is the first measurement of $CP$ violation in $B^0 to K^0pi^0$ decays reported by Belle II. The results agree with previous determinations and show a detector performance comparable with the best Belle results.
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