Malcolm John

Abstract:

The first observation of the decay B0s → χc1φ and a study of B0 → χc1,2K*0 decays are presented. The analysis is performed using a dataset, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. The following ratios of branching fractions are measured: Where the third uncertainty is due to the limited knowledge of the branching fractions of χc → J/ψγ modes. © 2013 CERN. Published by Elsevier B.V.

Abstract:

The LHCb experiment has been taking data at the Large Hadron Collider (LHC) at CERN since the end of 2009. One of its key detector components is the Ring-Imaging Cherenkov (RICH) system. This provides charged particle identification over a wide momentum range, from 2-100 GeV/c. The operation and control, software, and online monitoring of the RICH system are described. The particle identification performance is presented, as measured using data from the LHC. Excellent separation of hadronic particle types (π, K, p) is achieved. © 2013 CERN for the benefit of the LHCb collaboration.

Abstract:

A key ingredient to searches for physics beyond the Standard Model in Bs-0 mixing phenomena is the measurement of the B s-0 oscillation frequency, which is equivalent to the mass difference Δms of the Bs-0 mass eigenstates. Using the world's largest Bs-0 meson sample accumulated in a dataset, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment at the CERN LHC in 2011, a measurement of Δms is presented. A total of about 34 000 B s-0 → Dsπ-+ signal decays are reconstructed, with an average decay time resolution of 44 fs. The oscillation frequency is measured to be Δms = 17.768 ± 0.023 (stat) ± 0.006 (syst) ps-1, which is the most precise measurement to date. © CERN 2013 for the benefit of the LHCb Collaboration, published under the terms of the Creative Commons Attribution 3.0 licence by IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Any further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation and DOI..

Abstract:

Using three- and four-body decays of D mesons produced in semileptonic b-hadron decays, precision measurements of D meson mass differences are made together with a measurement of the D 0 mass. The measurements are based on a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected in pp collisions at 7 TeV. Using the decay D 0 → K + K - K - π +, the D 0 mass is measured to be M(D0)=1864. 75± 0.15(stat)± 0.11(syst) MeV/c2. The mass differences M(D+)-M(D0=4.76± 0.12(stat)± MeV/c 2. M(Ds+)-M(D+)=98.68± 0.03(stat)± 0.04(syst) MeV/c2 are measured using the D 0 → K + K - π + π - and Ds+ to K+K -π+ modes. © 2013 CERN for the benefit of the LHCb collaboration.

Abstract:

The results of searches for Bs0 → J/ψ ppmacr; and B + → J/ψ pp̄ π+ decays are reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fb-1 of pp collisions, collected with the LHCb detector. An excess with 2.8 σ significance is seen for the decay B s0 → J/ψ ppmacr; and an upper limit on the branching fraction is set at the 90 % confidence level: B0 → J/ψ ppmacr; < 4.8 × 10-6, which is the first such limit. No significant signals are seen for B 0 → J/ψ pp̄ and B + → J/ψ pp̄ π + decays, for which the corresponding limits are set: B0 → J/ψ ppmacr; and B + → J/ψ pp̄ π+ < 5.2 × 10 -7, which significantly improves the existing limit; and B(B + → J/ψpp̄ π+)< 5.0 × 10 -7, which is the first limit on this branching fraction. © 2013 CERN for the benefit of the LHCb collaboration.