LHCb

Abstract:

The ratio of branching fractions RK/π ≡ ℬ(Bc+ → J/ψK+)/ℬ(Bc+ → J/ψπ+) is measured with pp collision data collected by the LHCb experiment at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. It is found to be RK/π = 0.079 ± 0.007 ± 0.003, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.

Abstract:

© 2016 The Author(s) Measurements of CP observables in B ± →DK ± and B ± →Dπ ± decays are presented where the D meson is reconstructed in the final states K ± π ∓ , π ± K ∓ , K + K − , π + π − , K ± π ∓ π + π − , π ± K ∓ π + π − and π + π − π + π − . This analysis uses a sample of charged B mesons from pp collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb −1 . Various CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle γ. The analysis of the four-pion D decay mode is the first of its kind.

Abstract:

A time-dependent angular analysis of Bs0 → ψ(2S)ϕ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0fb^−1 collected during Run 1 of the LHC. The CP-violating phase and decay-width difference of the Bs0 system are measured to be ϕs = 0.23−0.28+0.29 ± 0.02rad and ΔΓs = 0.066−0.044+0.041 ± 0.007ps^−1, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that ϕs and ΔΓs have been measured in a decay containing the ψ(2S) resonance.

Abstract:

A measurement of the production cross-section of Z bosons in pp collisions at √s=13 TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range 2.0 < η < 4.5, transverse momenta pT > 20 GeV and dilepton invariant mass in the range 60 < m(ℓℓ) < 120 GeV. The integrated cross-section from averaging the two final states is σZℓℓ = 194.3 ± 0.9 ± 3.3 ± 7.6 pb, where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable ϕη*.