Guy Wilkinson

Abstract:

The decays Bc+→J/ψDs+ and Bc+→J/ψDs*+ are observed for the first time using a dataset, corresponding to an integrated luminosity of 3 fb-1, collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of √s=7 and 8 TeV. The statistical significance for both signals is in excess of 9 standard deviations. The following ratios of branching fractions are measured to be B(Bc+→J/ ψDs+)B(Bc+→J/ψπ+)=2.90±0.57±0.24, B(Bc+→J/ψDs*+)B(Bc+→J/ψDs+)=2.37±0.56±0. 10, where the first uncertainties are statistical and the second systematic. The mass of the Bc+ meson is measured to be mBc+=6276.28±1. 44(stat)±0.36(syst) MeV/c2, using the Bc+→J/ψDs+ decay mode. © 2013 CERN.

Abstract:

The branching fractions of Ds meson decays serve to normalize many measurements of processes involving charm quarks. Using 586 pb^-1 of e+ e- collisions recorded at a center of mass energy of 4.17 GeV, we determine absolute branching fractions for 13 Ds decays in 16 reconstructed final states with a double tag technique. In particular we make a precise measurement of the branching fraction B(Ds -> K- K+ pi+) = (5.55 +- 0.14 +- 0.13)%, where the uncertainties are statistical and systematic respectively. We find a significantly reduced value of B(Ds -> pi+ pi0 eta') compared to the world average, and our results bring the inclusively and exclusively measured values of B(Ds -> eta' X)$ into agreement. We also search for CP-violating asymmetries in Ds decays and measure the cross-section of e+ e- -> Ds* Ds at Ecm = 4.17 GeV.

Abstract:

The time-dependent CP asymmetry in Bs0→J/ψK+K - decays is measured using pp collision data at √s=7 TeV, corresponding to an integrated luminosity of 1.0 fb-1, collected with the LHCb detector. The decay-time distribution is characterized by the decay widths ΓL and ΓH of the light and heavy mass eigenstates of the Bs0-B̄s0 system and by a CP-violating phase s. In a sample of 27 617 Bs0→J/ψK+K- decays, where the dominant contribution comes from Bs0→J/ψ decays, these parameters are measured to be s=0.07±0.09(stat) ±0.01(syst) rad, Γs≡(ΓL+Γ H)/2=0.663±0.005(stat)±0.006(syst) ps-1, and ΔΓs≡ΓL-ΓH=0. 100±0.016(stat)±0.003(syst) ps-1, corresponding to the single most precise determination of s, ΔΓs, and Γs. The result of performing a combined analysis with Bs0→J/ψπ+π- decays gives s=0.01±0.07(stat)±0.01(syst) rad, Γs= 0.661±0.004(stat)±0.006(syst) ps-1, and ΔΓs=0.106±0.011(stat)±0.007(syst) ps -1. All measurements are in agreement with the Standard Model predictions. © 2013 CERN. Published by the American Physical Society under the terms of the http://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Abstract:

First observations of the BS0→ψ(2S)η, B0→ψ(2S)π+π- and BS0→ψ(2S)π+π- decays are made using a dataset corresponding to an integrated luminosity of 1.0 fb-1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of √s=7 TeV. The ratios of the branching fractions of each of the ψ(2S) modes with respect to the corresponding J/ψ decays are where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the J/ψ and ψ(2S) meson decays. © 2013 CERN.