Abstract:

Measurements of charm mixing and CP violation parameters from the decay-time-dependent ratio of D⁰ K+π- to D⁰ K-π+ decay rates and the charge-conjugate ratio are reported. The analysis uses &Bmacr; D^*+μ-X, and charge-conjugate decays, where D^*+ D⁰π+, and D⁰ K∓π±. The pp collision data are recorded by the LHCb experiment at center-of-mass energies √_s=7 and 8 TeV, corresponding to an integrated luminosity of 3 fb^-1. The data are analyzed under three hypotheses: (i) mixing assuming CP symmetry, (ii) mixing assuming no direct CP violation in the Cabibbo-favored or doubly Cabibbo-suppressed decay amplitudes, and (iii) mixing allowing either direct CP violation and/or CP violation in the superpositions of flavor eigenstates defining the mass eigenstates. The data are also combined with those from a previous LHCb study of D⁰ Kπ decays from a disjoint set of D^*+ candidates produced directly in pp collisions. In all cases, the data are consistent with the hypothesis of CP symmetry.

Abstract:

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*}

Abstract:

A measurement of the phase difference between the short- and long-distance contributions to the B+→K+μ+μ− decay is performed by analysing the dimuon mass distribution. The analysis is based on pp collision data corresponding to an integrated luminosity of 3fb^-1 collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the B+→K+μ+μ− decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the J/ψ and ψ(2S) resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, C9 and C10, and the branching fraction of the short-distance component is measured.

Abstract:

The ratio of branching fractions and the difference in CP asymmetries of the decays B+ → J/ψπ+ and B+ → J/ψK+ are measured using a data sample of pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 3 fb^−1 at centre-of-mass energies of 7 and 8 TeV. The results are B(B+→J/ψπ+)/B(B+→J/ψK+)=(3.83±0.03±0.03)×10^−2, ACP(B+→J/ψπ+)−ACP(B+→J/ψK+)=(1.82±0.86±0.14)×10^−2, where the first uncertainties are statistical and the second are systematic. Combining this result with a recent LHCb measurement of A^CP (B+ → J/ψK+) provides the most precise estimate to date of CP violation in the decay B+→J/ψπ+, A^CP(B+→J/ψπ+)=(1.91±0.89±0.16)×10^−2..

Abstract:

Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb^-1, recorded by the LHCb detector at centre-of-mass energies of 7 and 8TeV, the B+c → D0K+ decay is observed with a statistical significance of 5.1 standard deviations. By normalising to B+ → D0π+ decays, a measurement of the branching fraction multiplied by the production rates for B+c relative to B+ mesons in the LHCb acceptance is obtained, RD0K = fc/fu X B(B+c → D0K+) = (9.3 +2.8/-2:5 ± 0.6) X 10^-7, where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first B+c decay of this nature to be observed.