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.
The production of $J/\psi$ mesons in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV is studied with the LHCb detector. Cross-section measurements are performed as a function ...of the transverse momentum $p_\mathrm{T}$ and the rapidity $y$ of the $J/\psi$ meson in the region $p_\mathrm{T}<14 \mathrm{GeV}/c$ and $2.0<y<4.5$, for both prompt $J/\psi$ mesons and $J/\psi$ mesons from $b$-hadron decays. The production cross-sections integrated over the kinematic coverage are $15.30\pm 0.03\pm 0.86$ $\mu$b for prompt $J/\psi$ and $2.34\pm 0.01\pm 0.13$ $\mu$b for $J/\psi$ from $b$-hadron decays, assuming zero polarization of the $J/\psi$ meson. The first uncertainties are statistical and the second systematic. The cross-section reported for $J/\psi$ mesons from $b$-hadron decays is used to extrapolate to a total $b\bar{b}$ cross-section. The ratios of the cross-sections with respect to $\sqrt{s}=8$ TeV are also determined.
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.
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.
A search for the rare decays B0s→π+π−μ+μ− and B0→π+π−μ+μ− is performed in a data set corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb detector in proton-proton collisions ...at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay B0s→π+π−μ+μ− and the first evidence of the decay B0→π+π−μ+μ− are obtained and the branching fractions are measured to be B(B0s→π+π−μ+μ−)=(8.6±1.5(stat)±0.7(syst)±0.7(norm))×10−8 and B(B0→π+π−μ+μ−)=(2.11±0.51(stat)±0.15(syst)±0.16(norm))×10−8, where the third uncertainty is due to the branching fraction of the decay B0→J/ψ(→μ+μ−)K∗(890)0(→K+π−), used as a normalisation.
An angular analysis of the decay B0s→K∗0K¯∗0 is performed using pp collisions corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment at a centre-of-mass energy s√=7 ...TeV. A combined angular and mass analysis separates six helicity amplitudes and allows the measurement of the longitudinal polarisation fraction fL=0.201±0.057(stat.)±0.040(syst.) for the B0s→K∗(892)0K¯∗(892)0 decay. A large scalar contribution from the K∗0(1430) and K∗0(800) resonances is found, allowing the determination of additional CP asymmetries. Triple product and direct CP asymmetries are determined to be compatible with the Standard Model expectations. The branching fraction B(B0s→K∗(892)0K¯∗(892)0) is measured to be (10.6±1.8(stat.)±1.0(syst.)±0.6(fd/fs))×10−6.
The differential branching fraction of the rare decay Λ0b→Λ0μ+μ− is measured as a function of q2, the square of the dimuon invariant mass. The analysis is performed using proton-proton collision ...data, corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment. Evidence of signal is observed in the q2 region below the square of the J/ψ mass. Integrating over 15<q2<20 GeV2/c4 the branching fraction is measured as dB(Λ0b→Λ0μ+μ−)/dq2=(1.18+0.09−0.08±0.03±0.27)×10−7(GeV2/c4)−1, where the uncertainties are statistical, systematic and due to the normalisation mode, Λ0b→J/ψΛ0, respectively. In the q2 intervals where the signal is observed, angular distributions are studied and the forward-backward asymmetries in the dimuon (AlFB) and hadron (AhFB) systems are measured for the first time. In the range 15<q2<20 GeV2/c4 they are found to be AlFB=−0.05±0.09 (stat)±0.03 (syst) and AhFB=−0.29±0.07 (stat)±0.03 (syst).
An angular analysis and a measurement of the differential branching fraction of the decay B0s→ϕμ+μ− are presented, using data corresponding to an integrated luminosity of 3.0fb−1 of pp collisions ...recorded by the LHCb experiment at s√=7 and 8TeV. Measurements are reported as a function of q2, the square of the dimuon invariant mass and results of the angular analysis are found to be consistent with the Standard Model. In the range 1
The first observation of the B0s→D∗∓sK± decay is reported using 3.0fb−1 of proton-proton collision data collected by the LHCb experiment. The D∗∓s mesons are reconstructed through the decay chain ...D∗∓s→γD∓s(K∓K±π∓). The branching fraction relative to that for B0s→D∗−sπ+ is measured to be 0.068±0.005+0.003−0.002, where the first uncertainty is statistical and the second is systematic. Using a recent measurement of BR(B0s→D∗−sπ+) the absolute branching fraction of B0s→D∗∓sK± is measured as ( 16.3 ± 1.2 (stat) +0.7−0.5 (syst) ± 4.8 (norm) ) × 10−5, where the third uncertainty is due to the uncertainty on the branching fraction of the normalisation channel.
The first measurement of decay-time-dependent CP asymmetries in the decay B0s→J/ψK0S and an updated measurement of the ratio of branching fractions B(B0s→J/ψK0S)/B(B0d→J/ψK0S)} are presented. The ...results are obtained using data corresponding to an integrated luminosity of 3.0 fb−1 of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The results on the CP asymmetries are AΔΓ(B0s→J/ψK0S)=0.49+0.77−0.65(stat)±0.06(syst), Cdir(B0s→J/ψK0S)=−0.28±0.41(stat)±0.08(syst) and Smix(B0s→J/ψK0S)=−0.08±0.40(stat)±0.08(syst). The ratio B(B0s→J/ψK0S)/B(B0d→J/ψK0S) is measured to be 0.0431±0.0017(stat)±0.0012(syst)±0.0025(fs/fd), where the last uncertainty is due to the knowledge of the B0s and B0d production fractions.
PDF
