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.
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.
A search for B0(s)→K0SK∗(892)0 decays is performed using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected with the LHCb detector at a centre-of-mass energy of 7 ...TeV. The B0s→K0SK∗(892)0 decay is observed for the first time, with a significance of 7.1 standard deviations. The branching fraction is measured to beB(B0s→K0SK∗(892)0)=(10.9±2.5±1.2)×10−6,where the first uncertainty is statistical and the second is systematic. No evidence is found for the decay B0→K0SK∗(892)0 and an upper limit is set on the branching fraction, B(B0→K0SK∗(892)0)<0.64 ×10−6, at 90% confidence level. All results are consistent with Standard Model predictions.
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.
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 time-dependent C P asymmetry in B 0 s → J / ψ K + K − decays is measured using p p collision data, corresponding to an integrated luminosity of 3.0 fb − 1 , collected with the LHCb detector ...at center-of-mass energies of 7 and 8 TeV. In a sample of 96 000 B 0 s → J / ψ K + K − decays, the C P -violating phase ϕ s is measured, as well as the decay widths Γ L and Γ H of the light and heavy mass eigenstates of the B 0 s - ¯ B 0 s system. The values obtained are ϕ s = − 0.058 ± 0.049 ± 0.006 rad , Γ s ≡ ( Γ L + Γ H ) / 2 = 0.6603 ± 0.0027 ± 0.0015 ps − 1 , and Δ Γ s ≡ Γ L − Γ H = 0.0805 ± 0.0091 ± 0.0032 ps − 1 , where the first uncertainty is statistical and the second, systematic. These are the most precise single measurements of those quantities to date. A combined analysis with B 0 s → J / ψ π + π − decays gives ϕ s = − 0.010 ± 0.039 rad . All measurements are in agreement with the standard model predictions. For the first time, the phase ϕ s is measured independently for each polarization state of the K + K − system and shows no evidence for polarization dependence.
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.
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 the C P violation observables S and C in the decays of B 0 and ¯ B 0 mesons to the J / ψ K 0 S final state. The data sample corresponds to an integrated luminosity of ...3.0 fb − 1 collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, and contains a total of 41 560 selected B 0 and ¯ B 0 decays. The analysis of the time evolution of these decays yields S = 0.731 ± 0.035 ( stat ) ± 0.020 ( syst ) and C = − 0.038 ± 0.032 ( stat ) ± 0.005 ( syst ) . In the standard model, S equals sin ( 2 β ) to a good level of precision. The values are consistent with the current world averages and with the standard model expectations.
Using the latest LHCb measurements of time-dependent CP violation in the B^0_s -> K^+K^- decay, a U-spin relation between the decay amplitudes of B^0_s -> K^+K^- and B^0 -> \pi^+\pi^- decay processes ...allows constraints to be placed on the angle gamma of the unitarity triangle and on the B^0_s mixing phase -2\beta_s. Results from an extended approach, which uses additional inputs on B^0 -> \pi^0\pi^0 and B^+ -> \pi^+\pi^0 decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value \gamma = ( 63.5 +7.2 -6.7 ) degrees modulo 180 degrees is determined. In an alternative analysis, the value -2\beta_s = -0.12 +0.14 -0.16 rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included.
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