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Abstract:

The oscillation frequency, Δ md, of B0 mesons is measured using semileptonic decays with a D- or D∗- meson in the final state. The data sample corresponds to 3.0fb-1 of pp collisions, collected by the LHCb experiment at centre-of-mass energies √s = 7 and 8 TeV. A combination of the two decay modes gives Δmd = (505.0 ± 2.1 ± 1.0) ns-1, where the first uncertainty is statistical and the second is systematic. This is the most precise single measurement of this parameter. It is consistent with the current world average and has similar precision.

Abstract:

The first study is presented of CP violation with an amplitude analysis of the Dalitz plot of B0 → DK+π- decays, with D→K+π-, K+K-, and π+π-. The analysis is based on a data sample corresponding to 3.0 fb-1 of pp collisions collected with the LHCb detector. No significant CP violation effect is seen, and constraints are placed on the angle γ of the unitarity triangle formed from elements of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. Hadronic parameters associated with the B0→DK∗(892)0 decay are determined for the first time. These measurements can be used to improve the sensitivity to γ of existing and future studies of the B0 → DK∗(892)0 decay.

Abstract:

A binned Dalitz plot analysis of the decays B 0 → DK ∗0, with D → K 0 S π + π − and D → K 0 S K + K −, is performed to measure the observables x ± and y ±, which are related to the CKM angle γ and the hadronic parameters of the decays. The D decay strong phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of the D decay model. With a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment, the values of the CP violation parameters are found to be x + = 0.05 ± 0.35 ± 0.02, x − = −0.31 ± 0.20 ± 0.04, y + = −0.81 ± 0.28 ± 0.06 and y − = 0.31 ± 0.21 ± 0.05, where the first uncertainties are statistical and the second systematic. These observables correspond to values γ = (71 ± 20)°, and . The parameters and are the magnitude ratio and strong phase difference between the suppressed and favoured B 0 decay amplitudes, and have been measured in a region of ±50 MeV/c 2 around the K ∗(892)0 mass and with the magnitude of the cosine of the K ∗(892)0 helicity angle larger than 0.4.

Abstract:

A study of the decay $D^{0}\rightarrow K^{-}\pi^{+}\mu^{+}\mu^{-}$ is performed using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2.0 fb$^{-1}$. Decay candidates with muon pairs that have an invariant mass in the range 675--875 MeV$/c^2$ are considered. This region is dominated by the $\rho^{0}$ and $\omega$ resonances. The branching fraction in this range is measured to be ${\cal B}$($D^{0}\rightarrow K^{-}\pi^{+}\mu^{+}\mu^{-}$ ) = $( 4.17 \pm 0.12(stat) \pm 0.40(syst) )\times10^{-6}$. This is the first observation of the decay $D^{0}\rightarrow K^{-}\pi^{+}\mu^{+}\mu^{-}$. Its branching fraction is consistent with the value expected in the Standard Model.