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Register a new userMeasurement of the charge asymmetry in $B^{pm}rightarrow phi K^{pm}$ and search for $B^{pm}rightarrow phi pi^{pm}$ decays
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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.
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Measurements of $C!P$ observables in $B^pm rightarrow D K^pm$ and $B^pm rightarrow D pi^pm$ decays are presented where the $D$ meson is reconstructed in the final states $K^pmpi^mp$, $pi^pm K^mp$, $K^+K^-$, $pi^+pi^-$, $K^pmpi^mp pi^+ pi^-$, $pi^pm K^mp pi^+ pi^-$ and $pi^+ pi^- pi^+ pi^-$. This analysis uses a sample of charged $B$ mesons from $pp$ collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb$^{-1}$. Various CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle $gamma$. The analysis of the four-pion $D$ decay mode is the first of its kind.
A search for $CP$ violation in $D^{pm}rightarrow eta^{prime} pi^{pm}$ and $D^{pm}_{s}rightarrow eta^{prime} pi^{pm}$ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of $3$ fb$^{-1}$, recorded by the LHCb experiment at centre-of-mass energies of $7$ and $8$ TeV. The measured $CP$-violating charge asymmetries are $A_{CP}(D^{pm} rightarrow eta^{prime} pi^{pm})=(-0.61pm 0.72 pm 0.53 pm 0.12)%$ and $A_{CP}(D^{pm}_{s}rightarrow eta^{prime} pi^{pm})=(-0.82pm 0.36 pm 0.22 pm 0.27)%$, where the first uncertainties are statistical, the second systematic, and the third are the uncertainties on the $A_{CP}(D^{pm} rightarrow K^0_S pi^{pm})$ and $A_{CP}(D^{pm}_{s}rightarrow phi pi^{pm})$ measurements used for calibration. The results represent the most precise measurements of these asymmetries to date.
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.
A search for CP violation in Cabibbo-suppressed $D^{pm}rightarrow K^0_{mathrm{S}} K^{pm}$ and $D^{pm}_{s}rightarrow K^0_{mathrm{S}} pi^{pm}$ decays is performed using $pp$ collision data, corresponding to an integrated luminosity of 3~fb$^{-1}$, recorded by the LHCb experiment. The individual $CP$-violating asymmetries are measured to be begin{eqnarray*} mathcal{A}_{CP}^{D^{pm}rightarrow K^0_{mathrm{S}} K^{pm}} & = & (+0.03 pm 0.17 pm 0.14) % mathcal{A}_{CP}^{D^{pm}_{s}rightarrow K^0_{mathrm{S}} pi^{pm}} & = & (+0.38 pm 0.46 pm 0.17) %, end{eqnarray*} assuming that $CP$ violation in the Cabibbo-favoured decays is negligible. A combination of the measured asymmetries for the four decay modes $D^{pm}_{(s)}rightarrow K^0_{mathrm{S}} K^{pm}$ and $D^{pm}_{(s)}rightarrow K^0_{mathrm{S}} pi^{pm}$ gives the sum [ mathcal{A}_{CP}^{D^{pm}rightarrow K^0_{mathrm{S}} K^{pm}} + mathcal{A}_{CP}^{D^{pm}_{s}rightarrow K^0_{mathrm{S}} pi^{pm}} = (+0.41 pm 0.49 pm 0.26) %. ] In all cases, the first uncertainties are statistical and the second systematic. The results represent the most precise measurements of these asymmetries to date and show no evidence for CP violation.
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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