Decays of ¯ B 0 s and ¯ B 0 mesons into J / ψ π + π − π + π − final states, produced in p p collisions at the LHC, are investigated using data corresponding to an integrated luminosity of 3 fb − ...1 collected with the LHCb detector. ¯ B 0 ( s ) → J / ψ f 1 ( 1285 ) decays are seen for the first time, and the branching fractions are measured. Using these rates, the f 1 ( 1285 ) mixing angle between strange and nonstrange components of its wave function in the q ¯ q structure model is determined to be ± ( 24 . 0 + 3.1 + 0.6 − 2.6 − 0.8 ) ° . Implications on the possible tetraquark nature of the f 1 ( 1285 ) are discussed.
We present a measurement of form-factor-independent angular observables in the decay B 0 → K ∗ ( 892 ) 0 μ + μ − . The analysis is based on a data sample corresponding to an integrated luminosity of ...1.0 fb − 1 , collected by the LHCb experiment in p p collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared q 2 in the range 0.1 < q 2 < 19.0 GeV 2 / c 4 . Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one q 2 bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%.
Observation of the Decay B+c→B0sπ Calvo Gómez, Míriam; Camboni, Alessandro; Comerma Montells, Albert ...
Physical review letters,
11/2013
Journal Article
Recenzirano
Odprti dostop
The result of a search for the decay B + c → B 0 s π + is presented, using the B 0 s → D − s π + and B 0 s → J / ψ ϕ channels. The analysis is based on a data sample of p p collisions collected with ...the LHCb detector, corresponding to an integrated luminosity of 1 fb − 1 taken at a center-of-mass energy of 7 TeV, and 2 fb − 1 taken at 8 TeV. The decay B + c → B 0 s π + is observed with significance in excess of 5 standard deviations independently in both decay channels. The measured product of the ratio of cross sections and branching fraction is σ ( B + c ) / σ ( B 0 s ) × B ( B + c → B 0 s π + ) = 2.37 ± 0.31 ( stat ) ± 0.11 ( syst ) + 0.17 − 0.13 ( τ B + c ) × 10 − 3 , in the pseudorapidity range 2 < η ( B ) < 5 , where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the B + c lifetime. This is the first observation of a B meson decaying to another B meson via the weak interaction.
A search for the rare decays B 0 s → μ + μ − and B 0 → μ + μ − is performed at the LHCb experiment. The data analyzed correspond to an integrated luminosity of 1 fb − 1 of p p collisions at a ...center-of-mass energy of 7 TeV and 2 fb − 1 at 8 TeV. An excess of B 0 s → μ + μ − signal candidates with respect to the background expectation is seen with a significance of 4.0 standard deviations. A time-integrated branching fraction of B ( B 0 s → μ + μ − ) = ( 2.9 + 1.1 − 1.0 ) × 10 − 9 is obtained and an upper limit of B ( B 0 → μ + μ − ) < 7.4 × 10 − 10 at 95% confidence level is set. These results are consistent with the standard model expectations.
The ratio of the Λ 0 b baryon lifetime to that of the ¯¯¯ B 0 meson is measured using 1.0 fb − 1 of integrated luminosity in 7 TeV center-of-mass energy p p collisions at the LHC. The Λ 0 b ...baryon is observed for the first time in the decay mode Λ 0 b → J / ψ p K − , while the ¯¯¯ B 0 meson decay used is the well known ¯¯¯ B 0 → J / ψ π + K − mode, where the π + K − mass is consistent with that of the ¯¯¯¯ K * 0 ( 892 ) meson. The ratio of lifetimes is measured to be 0.976 ± 0.012 ± 0.006 , in agreement with theoretical expectations based on the heavy quark expansion. Using previous determinations of the ¯¯¯ B 0 meson lifetime, the Λ 0 b lifetime is found to be 1.482 ± 0.018 ± 0.012 ps . In both cases, the first uncertainty is statistical and the second systematic.
A search for charmless three-body decays of B 0 and B0s mesons with a K0S meson in the final state is performed using the pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, ...collected at a centre-of-mass energy of 7 TeV recorded by the LHCb experiment. Branching fractions of the B0(s)→K0Sh+h′− decay modes (h (′) = π, K), relative to the well measured B0→K0Sπ+π− decay, are obtained. First observation of the decay modes B0s→K0SK±π∓ and B0s→K0Sπ+π− and confirmation of the decay B0→K0SK±π∓ are reported. The following relative branching fraction measurements or limits are obtained $ B(B0→K0SK±π∓)B(B0→K0Sπ+π−)=0.128±0.017(stat.)±0.009(syst.),B(B0→K0SK+K−)B(B0→K0Sπ+π−)=0.385±0.031(stat.)±0.023(syst.),B(B0s→K0Sπ+π−)B(B0→K0Sπ+π−)=0.29±0.06(stat.)±0.03(syst.)±0.02(fs/fd),B(B0s→K0SK±π∓)B(B0→K0Sπ+π−)=1.48±0.12(stat.)±0.08(syst.)±0.12(fs/fd)B(B0s→K0SK+K−)B(B0→K0Sπ+π−)∈0.004;0.068at90%CL.
Direct and mixing-induced CP-violating asymmetries in B0s→K+K− decays are measured for the first time using a data sample of pp collisions, 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 results are C KK = 0.14 ± 0.11 ± 0.03 and S KK = 0.30 ± 0.12 ± 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B 0 → π + π − decays to be C ππ = −0.38 ± 0.15 ± 0.02 and S ππ = −0.71 ± 0.13 ± 0.02, in good agreement with existing measurements.
Prompt production of charmonium χ c0, χ c1 and χ c2 mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of TeX TeV. The χ c mesons are identified through their ...decay to J/ψγ, with J/ψ → μ + μ − using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb detector, is used to measure the relative prompt production rate of χ c1 and χ c2 in the rapidity range 2.0 < y < 4.5 as a function of the J/ψ transverse momentum from 3 to 20 GeV/c. First evidence for χ c0 meson production at a high-energy hadron collider is also presented.
A search for charmless three-body decays of B 0 and B0s mesons with a K0S meson in the final state is performed using the pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, ...collected at a centre-of-mass energy of 7 TeV recorded by the LHCb experiment. Branching fractions of the B0(s)→K0Sh+h′− decay modes (h (′) = π, K), relative to the well measured B0→K0Sπ+π− decay, are obtained. First observation of the decay modes B0s→K0SK±π∓ and B0s→K0Sπ+π− and confirmation of the decay B0→K0SK±π∓ are reported. The following relative branching fraction measurements or limits are obtained $ B(B0→K0SK±π∓)B(B0→K0Sπ+π−)=0.128±0.017(stat.)±0.009(syst.),B(B0→K0SK+K−)B(B0→K0Sπ+π−)=0.385±0.031(stat.)±0.023(syst.),B(B0s→K0Sπ+π−)B(B0→K0Sπ+π−)=0.29±0.06(stat.)±0.03(syst.)±0.02(fs/fd),B(B0s→K0SK±π∓)B(B0→K0Sπ+π−)=1.48±0.12(stat.)±0.08(syst.)±0.12(fs/fd)B(B0s→K0SK+K−)B(B0→K0Sπ+π−)∈0.004;0.068at90%CL.
Direct and mixing-induced CP-violating asymmetries in B0s→K+K− decays are measured for the first time using a data sample of pp collisions, 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 results are C KK = 0.14 ± 0.11 ± 0.03 and S KK = 0.30 ± 0.12 ± 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B 0 → π + π − decays to be C ππ = −0.38 ± 0.15 ± 0.02 and S ππ = −0.71 ± 0.13 ± 0.02, in good agreement with existing measurements.
