A binned Dalitz plot analysis of the decays B0→DK∗0, with D→K0Sπ+π− and K0SK+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 3.0fb−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)∘, rB0=0.56±0.17 and δB0=(204+21−20)∘. The parameters rB0 and δB0 are the magnitude ratio and strong phase difference between the suppressed and favoured B0 decay amplitudes, and have been measured in a region of ±50 MeV/c2 around the K∗(892)0 mass and with the magnitude of the cosine of the K∗(892)0 helicity angle larger than 0.4.
Measurements are presented of the branching fractions of the decays B0s→D∓sK± and B0→D−sK+ relative to the decays B0s→D−sπ+ and B0→D−π+, respectively. The data used correspond to an integrated ...luminosity of 3.0 fb−1 of proton-proton collisions. The ratios of branching fractions are B(B0s→D∓sK±)B(B0s→D−sπ+)=0.0752±0.0015±0.0019 and B(B0→D−sK+)B(B0→D−π+)=0.0129±0.0005±0.0008, where the uncertainties are statistical and systematic, respectively.
Time-dependent CP asymmetries in the decay rates of the singly Cabibbo-suppressed decays D0→K−K+ and D0→π−π+ are measured in pp collision data corresponding to an integrated luminosity of 3.0 fb−1 ...collected by the LHCb experiment. The D0 mesons are produced in semileptonic b-hadron decays, where the charge of the accompanying muon is used to determine the initial state as D0 or D¯0. The asymmetries in effective lifetimes between D0 and D¯0 decays, which are sensitive to indirect CP violation, are determined to beAΓ(K−K+)=(−0.134±0.077+0.026−0.034)% ,AΓ(π−π+)=(−0.092±0.145+0.025−0.033)% ,where the first uncertainties are statistical and the second systematic. This result is in agreement with previous measurements and with the hypothesis of no indirect CP violation in D0 decays.
A search is performed for the charmless three-body decays of the Λ0b and Ξ0b baryons to the final states Λh+h′−, where h(′)=π or K. The analysis is based on a data sample, corresponding to an ...integrated luminosity of 3fb−1 of pp collisions, collected by the LHCb experiment. The Λ0b→ΛK+π− and Λ0b→ΛK+K− decays are observed for the first time and their branching fractions and CP asymmetry parameters are measured. Evidence is seen for the Λ0b→Λπ+π− decay and limits are set on the branching fractions of Ξ0b baryon decays to the Λh+h′− final states.
We perform a search for near-threshold Ξ0b resonances decaying to Ξ−bπ+ in a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb ...experiment. We observe one resonant state, with the following properties:m(Ξ∗0b)−m(Ξ−b)−m(π+)=15.727±0.068(stat)±0.023(syst)MeV/c2,Γ(Ξ∗0b)=0.90±0.16(stat)±0.08(syst)MeV.This confirms the previous observation by the CMS collaboration. The state is consistent with the JP=3/2+ Ξ∗0b resonance expected in the quark model. This is the most precise determination of the mass and the first measurement of the natural width of this state. We have also measured the ratioσ(pp→Ξ∗0bX)B(Ξ∗0b→Ξ−bπ+)σ(pp→Ξ−bX)=0.27±0.03(stat)±0.01(syst).
The decay B¯¯¯0s→ψ(2S)K+π− is observed using a data set corresponding to an integrated luminosity of 3.0fb−1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 ...TeV. The branching fraction relative to the B0→ψ(2S)K+π− decay mode is measured to beB(B¯¯¯0s→ψ(2S)K+π−)B(B0→ψ(2S)K+π−)=5.38±0.36(stat)±0.22(syst)±0.31(fs/fd)%,where fs/fd indicates the uncertainty due to the ratio of probabilities for a b quark to hadronise into a B0s or B0 meson. Using an amplitude analysis, the fraction of decays proceeding via an intermediate K∗(892)0 meson is measured to be 0.645±0.049(stat)±0.049(syst) and its longitudinal polarisation fraction is 0.524±0.056(stat)±0.029(syst). The relative branching fraction for this component is determined to beB(B¯¯¯0s→ψ(2S)K∗(892)0)B(B0→ψ(2S)K∗(892)0)=5.58±0.57(stat)±0.40(syst)±0.32(fs/fd)%.In addition, the mass splitting between the B0s and B0 mesons is measured asM(B0s)−M(B0)=87.45±0.44(stat)±0.07(syst)MeV/c2.
The first observation of the B 0 s → η ′ η ′ decay is reported. The study is based on a sample of proton-proton collisions corresponding to 3.0 fb − 1 of integrated luminosity collected with the ...LHCb detector. The significance of the signal is 6.4 standard deviations. The branching fraction is measured to be 3.31 ± 0.64 ( stat ) ± 0.28 ( syst ) ± 0.12 ( norm ) × 10 − 5 , where the third uncertainty comes from the B ± → η ′ K ± branching fraction that is used as a normalization. In addition, the charge asymmetries of B ± → η ′ K ± and B ± → ϕ K ± , which are control channels, are measured to be ( − 0.2 ± 1.3 ) % and ( + 1.7 ± 1.3 ) % , respectively. All results are consistent with theoretical expectations.
Measurements are presented of electroweak boson production using data from pp collisions at a centre-of-mass energy of s√=8TeV. The analysis is based on an integrated luminosity of 2.0fb−1 recorded ...with the LHCb detector. The bosons are identified in the W→μν and Z→μ+μ− decay channels. The cross-sections are measured for muons in the pseudorapidity range 2.0<η<4.5, with transverse momenta pT>20GeV/c and, in the case of the Z boson, a dimuon mass within 60<Mμ+μ−<120GeV/c2. The results areσW+→μ+νσW−→μ−ν¯σZ→μ+μ−=1093.6±2.1±7.2±10.9±12.7pb,=818.4±1.9±5.0±7.0±9.5pb,=95.0±0.3±0.7±1.1±1.1pb,where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. The evolution of the W and Z boson cross-sections with centre-of-mass energy is studied using previously reported measurements with 1.0fb−1 of data at 7TeV. Differential distributions are also presented. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics.
The branching fraction ratio R(D∗)≡B(B¯¯¯0→D∗+τ−ν¯τ)/B(B¯¯¯0→D∗+μ−ν¯μ) is measured using a sample of proton-proton collision data corresponding to 3.0\invfb of integrated luminosity recorded by the ...LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ−→μ−ν¯μντ. The semitauonic decay is sensitive to contributions from non-Standard-Model particles that preferentially couple to the third generation of fermions, in particular Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate B¯¯¯0 decays gives R(D∗)=0.336±0.027(stat)±0.030(syst). This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the Standard Model.
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