Abstract:

Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5TeV. The data sample corresponds to an integrated luminosity of 8:60 ± 0:33 pb^-1 collected by the LHCb experiment. The production cross-sections of D0, D+, D+s, and D*+ mesons are measured in bins of charm meson transverse momentum, pT, and rapidity, y. They cover the rapidity range 2:0 < y < 4:5 and transverse momentum ranges 0 < pT < 10 GeV=c for D0 and D+ and 1 < pT < 10 GeV=c for D+s and D*+ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1 < pT < 8 GeV=c are determined to be

σ(pp → D0X) = 1004 ± 3 ± 54 μb;

σ(pp → D+X) = 402 ± 2 ± 30 μb;

σ(pp → D+s X) = 170 ± 4 ± 16 μb;

σ(pp → D*+X) = 421 ± 5 ± 36 μb

where the uncertainties are statistical and systematic, respectively.

Abstract:

A search for CP violation in the decay Λb0 → pK−μ+μ− is presented. This decay is mediated by flavour-changing neutral-current transitions in the Standard Model and is potentially sensitive to new sources of CP violation. The study is based on a data sample of proton-proton collisions recorded with the LHCb experiment, corresponding to an integrated luminosity of 3 fb^−1. The Λb0 → pK−μ+μ− decay is observed for the first time, and two observables that are sensitive to different manifestations of CP violation are measured, ΔACP ≡ ACP(Λ0b→pK−μ+μ−) − ACP(Λ0b→pK−J/ψ) and a aT-odd/CP, where the latter is based on asymmetries in the angle between the μ+μ− and pK− decay planes. These are measured to be ΔACP = (−3.5 ±5.0(stat) ±0.2(syst))×10^−2, aT-odd/CP = (1.2 ±5.0 (stat) ±0.7 (syst))×10^−2,and no evidence for CP violation is found.

Abstract:

The observation of the decay Ξ b − →J/ψΛK − is reported, using a data sample corresponding to an integrated luminosity of 3fb −1 , collected by the LHCb detector in pp collisions at centre-of-mass energies of 7 and 8TeV. The production rate of Ξ b − baryons detected in the decay Ξ b − →J/ψΛK − is measured relative to that of Λ b 0 baryons using the decay Λ b 0 →J/ψΛ. Integrated over the b-baryon transverse momentum p T < 25GeV/c and rapidity 2.0 < y < 4.5, the measured ratio is [Formula presented][Formula presented] =(4.19±0.29 (stat)±0.15 (syst))×10 −2 , where f Ξ b − and f Λ b 0 are the fragmentation fractions of b→Ξ b − and b→Λ b 0 transitions, and B represents the branching fraction of the corresponding b-baryon decay. The mass difference between Ξ b − and Λ b 0 baryons is measured to be M(Ξ b − )−M(Λ b 0 )=177.08±0.47 (stat)±0.16 (syst)MeV/c 2 .

Abstract:

A search for the rare decays B0s→ τþτ− and B0 → τþτ− is performed using proton–proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3 fb^−1 collected in 2011 and 2012. The τ leptons are reconstructed through the decay τ− → π−π+π−ντ. Assuming no contribution from B0 → τþτ− decays, an upper limit is set on the branching fraction B(B0s → τ+τ−) < 6.8 × 10^−3 at the 95% confidence level. If instead no contribution from B0s → τ+τ− decays is assumed, the limit is B(B0 → τþτ−) < 2.1 × 10^−3 at the 95% confidence level. These results correspond to the first direct limit on B(B0s→ τ+τ−) and the world’s best limit on B(B0 → τ+τ−).

Abstract:

The production of J/ψ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the J/ψ meson, z(J/ψ)≡p_{T}(J/ψ)/p_{T}(jet), is measured using jets with p_{T}(jet)>20  GeV in the pseudorapidity range 2.5<η(jet)<4.0. The observed z(J/ψ) distribution for J/ψ mesons produced in b-hadron decays is consistent with expectations. However, the results for prompt J/ψ production do not agree with predictions based on fixed-order nonrelativistic QCD. This is the first measurement of the p_{T} fraction carried by prompt J/ψ mesons in jets at any experiment.