The difference in total widths between the B+c and B+ mesons is measured using 3.0fb−1 of data collected by the LHCb experiment in 7 and 8 TeV centre-of-mass energy proton-proton collisions at the ...LHC. Through the study of the time evolution of B+c→J/ψπ+ and B+→J/ψK+ decays, the width difference is measured to beΔΓ≡ΓB+c−ΓB+=4.46±0.14±0.07mm−1c,where the first uncertainty is statistical and the second systematic. The known lifetime of the B+ meson is used to convert this to a precise measurement of the B+c lifetime,τB+c=513.4±11.0±5.7fs,where the first uncertainty is statistical and the second systematic.
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.
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.
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.
A study of $B^0$~and $B^0_s$ meson decays into $J/\psi\eta$~and $J/\psi\eta^{\prime}$ final states is performed using a data set of proton-proton collisions at centre-of-mass energies of 7 and 8TeV, ...collected by the LHCb experiment and corresponding to 3.0fb$^{-1}$ of integrated luminosity. The decay $B^0 \rightarrow J/\psi \eta^{\prime}$ is observed for thefirst time. The following ratios of branching fractions are measured: $$ \frac{\mathcal{B}(B^0 \rightarrow J/\psi \eta^{\prime})}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta^{\prime})} = (2.28\pm0.65\,(stat)\,\pm0.10\,(syst)\,\pm0.13\,(f_{s}/f_{d}))\times10^{-2},$$ $$ \frac{\mathcal{B}(B^0 \rightarrow J/\psi \eta)}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta)} = (1.85\pm0.61\,(stat)\,\pm0.09\,(syst)\,\pm0.11\,(f_{s}/f_{d}))\times10^{-2},$$ where the third uncertainty is related to the present knowledge of $f_{s}/f_{d}$, the ratio between the probabilities for a $b$ quark to form a $B^0_s$ or $B^0$ meson. The branching fraction ratios are used to determine the parameters of $\eta-\eta^{\prime}$ meson mixing. In addition, the first evidence for the decay $B^0_s \rightarrow \psi(2S) \eta^{\prime}$ is reported, and the relative branching fraction is measured,$$\frac{\mathcal{B}(B^0_s \rightarrow \psi(2S) \eta^{\prime})}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta^{\prime})} = (38.7\pm9.0\,(stat)\,\pm1.3\,(syst)\,\pm0.9(\mathcal{B}))\times10^{-2},$$where the third uncertainty is due to the limited knowledge of the branching fractions of $J/\psi$ and $\psi(2S)$~mesons.
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.
A measurement of the cross-section for Z-boson production in the forward region of pp collisions at 8TeV centre-of-mass energy is presented. The measurement is based on a sample of Z→e+e− decays ...reconstructed using the LHCb detector, corresponding to an integrated luminosity of 2.0fb−1. The acceptance is defined by the requirements 2.0<η<4.5 and pT>20GeV for the pseudorapidities and transverse momenta of the leptons. Their invariant mass is required to lie in the range 60--120GeV. The cross-section is determined to beσ(pp→Z→e+e−)=93.81±0.41(stat)±1.48(syst)±1.14(lumi)pb,where the first uncertainty is statistical and the second reflects all systematic effects apart from that arising from the luminosity, which is given as the third uncertainty. Differential cross-sections are presented as functions of the Z-boson rapidity and of the angular variable ϕ∗, which is related to the Z-boson transverse momentum.
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