LHCb

Abstract:

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 search for the decays of the B+c meson to ppπ+ is performed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb-1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. No signal is found and an upper limit, at 95% confidence level, is set, fc/fu × B(B+c → ppπ+) < 3.6×10^-8 in the kinematic region m(pp) < 2.85 GeV/c^2, pT(B) < 20 GeV/c and 2.0 < y(B) < 4.5, where B is the branching fraction and fc(fu) is the fragmentation fraction of the b quark into a Bc+ (B+) meson.

Abstract:

The decays Λb0→ ψ(2S)pK− and Λb0→ J/ψπ+π−pK−are observed in a data sample corresponding to an integrated luminosity of 3 fb^−1, collected in proton-proton collisions at 7 and 8 TeV centre-of-mass energies by the LHCb detector. The ψ(2S) mesons are reconstructed through the decay modes ψ(2S) → μ+μ−and ψ(2S) → J/ψπ+π−. The branching fractions relative to that of Λb0→ J/ψpK−are measured to be ℬ(Λb0→ψ(2S)pK−)/ℬ(Λb0→J/ψpK−) = (20.70±0.76±0.46±0.37) × 10^−2, ℬ(Λb0→ψ(2S)pK−)/ℬ(Λb0→J/ψpK−) = (20.86±0.96±1.34)×10^−2 where the first uncertainties are statistical, the second are systematic and the third is related to the knowledge of J/ψ and ψ(2S) branching fractions. The mass of the Λb0baryon is measured to be M(Λb0) = 5619.65 ± 0.17 ± 0.17MeV/c2, where the uncertainties are statistical and systematic.

Abstract:

A proton-proton collision data sample, corresponding to an integrated luminosity of 3fb−1 collected by LHCb at √s = 7 and 8 TeV, is used to reconstruct 63 ± 9 Ωb- → Ω0cπ−, Ω0c → pK−K−π+ decays. Using the Ξ−b → Ξ0cπ−, Ξ0c → pK−K−π+ decay mode for calibration, the lifetime ratio and the absolute lifetime of the Ω−b baryon are measured to be τΩ−b/τΞ−b = 1.11 ± 0.16 ± 0.03, τΩb− = 1.78 ± 0.26 ± 0.05 ± 0.06 ps, where the uncertainties are statistical, systematic and from the calibration mode (for τΩb- only). A measurement is also made of the mass difference, mΩb- − mΞb-, and the corresponding Ωb- mass, which yields mΩb- − mΞb- = 247.4 ±3.2 ±0.5  MeV/c2, mΩb- = 6045.1 ± 3.2 ± 0.5 ± 0.6  MeV/c2. These results are consistent with previous measurements.