Guy Wilkinson

Abstract:

© CERN 2014. All rights reserved. The production of Xb mesons in proton-proton collisions is studied using a data sample collected by the LHCb detector, at centre-of-mass energies of √s = 7 and 8TeV and corresponding to an integrated luminosity of 3.0 fb⁻¹. The Xb mesons are identified through their decays to γ(1S) and γ(2S)γ using photons that converted to e⁺e⁻ pairs in the detector. The relative prompt production rate of Xb1(1P) and Xb2(1P) mesons is measured as a function of the X(1S) transverse momentum in the Xb rapidity range 2.0 < y < 4.5. A precise measurement of the Xb(3P) mass is also performed. Assuming a mass splitting between the Xb1(3P) and the Xb2(3P) states of 10.5 MeV/c2, the measured mass of the Xb1(3P) meson is m(Xb1(3P)) = 10515.7^+2.2−3.9(stat)^+1.5−2.1(syst)MeV/c².

Abstract:

© CERN 2014. All rights reserved. The production of Xb mesons in proton-proton collisions is studied using a data sample collected by the LHCb detector, at centre-of-mass energies of √s = 7 and 8TeV and corresponding to an integrated luminosity of 3.0 fb−1. The Xb mesons are identified through their decays to γ(1S) and γ(2S)γ using photons that converted to e+e− pairs in the detector. The relative prompt production rate of Xb1(1P) and Xb2(1P) mesons is measured as a function of the X(1S) transverse momentum in the Xb rapidity range 2.0 < y < 4.5. A precise measurement of the Xb(3P) mass is also performed. Assuming a mass splitting between the Xb1(3P) and the Xb2(3P) states of 10.5 MeV/c2, the measured mass of the Xb1(3P) meson is m(Xb1(3P)) = 10515.7+2.2 −3.9(stat)+1.5 −2.1(syst)MeV/c2.

Abstract:

© The Authors. The first observation of the Cabibbo-suppressed decay V0b→ J/ψpπ−is reported using a data sample of proton-proton collisions at 7 and 8TeV, corresponding to an integrated luminosity of 3 fb−1. A prominent signal is observed and the branching fraction relative to the decay mode V0b→ J/ψpK−is determined to be B[Equations Found] A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be [Equations Found], which is compatible with CP symmetry at the 2.2σ level.

Abstract:

© 2014, Springer Verlag. All rights reserved. A search for CP violation in Cabibbo-suppressed D± → K0 SK± and D± s → K0 Sπ± decays is performed using pp collision data, corresponding to an integrated luminosity of 3 fb-1, recorded by the LHCb experiment. The individual CP-violating asymmetries are measured to be (Formula presented.) assuming that CP violation in the Cabibbo-favoured decays is negligible. A combination of the measured asymmetries for the four decay modes D± (s) → K0 SK± and D± (s) → K0 Sπ± gives the sum (Formula presented.). In all cases, the first uncertainties are statistical and the second systematic. The results represent the most precise measurements of these asymmetries to date and show no evidence for CP violation.

Abstract:

A search for previously unobserved decays of beauty baryons to the final states K0 spπ- and K0 spK- is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb- of pp collisions. The Λ0 b → ̄K pπ- decay is observed with a significance of 8.6σ, with branching fraction (Equation Presented), where the uncertainties are statistical, systematic, from the ratio of fragmentation fractions f Λ 0 b/fd, and from the branching fraction of the B0 → K0π+π - normalisation channel, respectively. A first measurement is made of the CP asymmetry, giving (Equation Presented). No significant signals are seen for Λ0 b → K0 spK - decays, Ξ0 b decays to both the K 0 spπ- and K0 spK - final states, and the Λ0 b → D- s(→ K0 sK-)p decay, and upper limits on their branching fractions are reported.