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Register a new userMeasurement of the $B^{pm}$ production asymmetry and the $CP$ asymmetry in $B^{pm} to J/psi K^{pm}$ decays
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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*}
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Measurements of $CP$ observables in $B^pm rightarrow D^{(*)} K^pm$ and $B^pm rightarrow D^{(*)} pi^pm$ decays are presented, where $D^{(*)}$ indicates a neutral $D$ or $D^*$ meson that is an admixture of $D^{(*)0}$ and $bar{D}^{(*)0}$ states. Decays of the $D^*$ meson to the $Dpi^0$ and $Dgamma$ final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the $B$ candidate invariant mass distribution. Decays of the $D$ meson are fully reconstructed in the $K^pm pi^mp$, $K^+ K^-$ and $pi^+ pi^-$ final states. The analysis uses a sample of charged $B$ mesons produced in $pp$ collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb$^{-1}$ taken at centre-of-mass energies of $sqrt{s}$ = 7, 8 and 13 TeV, respectively. The study of $B^{pm} to D^{*} K^{pm}$ and $B^{pm} to D^{*} pi^{pm}$ decays using a partial reconstruction method is the first of its kind, while the measurement of $B^{pm} to D K^{pm}$ and $B^{pm} to D pi^{pm}$ decays is an update of previous LHCb measurements. The $B^{pm} to D K^{pm}$ results are the most precise to date.
The CP-violating charge asymmetry in $B^{pm}rightarrow phi K^{pm}$ decays is measured in a sample of $pp$ collisions at 7 TeV centre-of-mass energy, corresponding to an integrated luminosity of 1.0 fb$^{-1}$ collected by the LHCb experiment. The result is $mathcal{A}_{CP}(B^{pm}rightarrow phi K^{pm}) = rm 0.022pm 0.021 pm 0.009$, where the first uncertainty is statistical and the second systematic. In addition, a search for the $B^{pm}rightarrow phi pi^{pm}$ decay mode is performed, using the $B^{pm}rightarrow phi K^{pm}$ decay rate for normalization. An upper limit on the branching fraction $mathcal{B}(B^{pm}rightarrow phi pi^{pm})< 1.5times 10^{-7}$ is set at 90% confidence level.
We report on measurements of the time-dependent CP violating observables in $B^0_srightarrow D^{mp}_s K^{pm}$ decays using a dataset corresponding to 1.0 fb$^{-1}$ of pp collisions recorded with the LHCb detector. We find the CP violating observables $C_f=0.53pm0.25pm0.04$, $A^{DeltaGamma}_f=0.37pm0.42pm0.20$, $A^{DeltaGamma}_{bar{f}}=0.20pm0.41pm0.20$, $S_f=-1.09pm0.33pm0.08$, $S_{bar{f}}=-0.36pm0.34pm0.08$, where the uncertainties are statistical and systematic, respectively. Using these observables together with a recent measurement of the $B^0_s$ mixing phase $-2beta_s$ leads to the first extraction of the CKM angle $gamma$ from $B^0_s rightarrow D^{mp}_s K^{pm}$ decays, finding $gamma$ = (115$_{-43}^{+28}$)$^circ$ modulo 180$^circ$ at 68% CL, where the error contains both statistical and systematic uncertainties.
We analyze the asymmetry in the partial widths for the decays $B^{pm} to M {bar M} pi^{pm}$ ($ M = pi^+, K ^+, pi^0, eta$), which results from the interference of the nonresonant decay amplitude with the resonant amplitude for $B^{pm} to chi_{c0} pi^{pm} $ followed by the decay $chi_{c0} to M {bar M} $. The CP violating phase $gamma$ can be extracted from the measured asymmetry. We find that the partial width asymmetry for $B^pm to pi^+ pi^- pi^pm$ is about $0.33~sin gamma$, and about $0.45~ sin gamma$ for $B^pm to K^+ K^-pi^pm$, while it is somewhat smaller for $B^pm to pi^0 pi^0 pi^pm$ and $B^pm to eta eta pi^pm$. Potential sources of uncertainties in these results, primarily coming from poorly known input parameters, are discussed.
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