Malcolm John

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.

Abstract:

©Open Access. The production of J/ψ mesons with rapidity 1.5 < y < 4.0 or −5.0 < y < −2.5 and transverse momentum pT < 14 GeV/c is studied with the LHCb detector in proton-lead collisions at a nucleon-nucleon centre-of-mass energy √SNN = 5 TeV. The J/ψ mesons are reconstructed using the dimuon decay mode. The analysis is based on a data sample corresponding to an integrated luminosity of about 1.6 nb−1. For the first time the nuclear modification factor and forward-backward production ratio are determined separately for prompt J/ψ mesons and J/ψ from b-hadron decays. Clear suppression of prompt J/ψ production with respect to proton-proton collisions at large rapidity is observed, while the production of J/ψ from b-hadron decays is less suppressed. These results show good agreement with available theoretical predictions. The measurement shows that cold nuclear matter effects are important for interpretations of the related quark-gluon plasma signatures in heavy-ion collisions.

Abstract:

The LHCb RICH1 detector uses hybrid photon detectors (HPDs) as its optical sensors. A calibration system has been constructed to provide corrections for distortions that are primarily due to external magnetic fields. We describe here the system design, construction, operation and performance. © 2013 Elsevier B.V.