Determination of the sign of the decay width difference in the bs0 system
Physical Review Letters 108:24 (2012)
Abstract:
The interference between the K +K - S-wave and P-wave amplitudes in Bs0→J/ψK +K - decays with the K +K - pairs in the region around the (1020) resonance is used to determine the variation of the difference of the strong phase between these amplitudes as a function of K +K - invariant mass. Combined with the results from our CP asymmetry measurement in Bs0→J/ψ decays, we conclude that the Bs0 mass eigenstate that is almost CP=+1 is lighter and decays faster than the mass eigenstate that is almost CP=-1. This determines the sign of the decay width difference ΔΓ sΓ L-Γ H to be positive. Our result also resolves the ambiguity in the past measurements of the CP violating phase s to be close to zero rather than π. These conclusions are in agreement with the standard model expectations. © 2012 CERN.Searches for Majorana neutrinos in B - decays
Physical Review D - Particles, Fields, Gravitation and Cosmology 85:11 (2012)
Abstract:
Searches for heavy Majorana neutrinos in B - decays in final states containing hadrons plus a μ -μ - pair have been performed using 0.41fb -1 of data collected with the LHCb detector in proton-proton collisions at a center-of-mass energy of 7 TeV. The D +μ -μ - and D *+μ -μ - final states can arise from the presence of virtual Majorana neutrinos of any mass. Other final states containing π +, Ds+, or D0π + can be mediated by an on-shell Majorana neutrino. No signals are found and upper limits are set on Majorana neutrino production as a function of mass, and also on the B - decay branching fractions. © 2012 CERN. Published by the American Physical Society.Measurement of ϒ production in pp collisions at √s =7 TeV
European Physical Journal C 72:6 (2012)
Abstract:
The production of ϒ (1S), ϒ (2S) and ϒ (3S) mesons in proton-proton collisions at the centre-of-mass energy of √s = 7 TeV is studied with the LHCb detector. The analysis is based on a data sample of 25 pb−1 collected at the Large Hadron Collider. The ϒ mesons are reconstructed in the decay mode ϒ →μ + μ − and the signal yields are extracted from a fit to the μ + μ − invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the ϒ transverse momentum pT and rapidity y, over the range pT < 15 GeV/c and 2.0Opposite-side flavour tagging of B mesons at the LHCb experiment
European Physical Journal C 72:6 (2012)
Abstract:
The calibration and performance of the opposites-ide flavour tagging algorithms used for the measurements of time-dependent asymmetries at the LHCb experiment are described. The algorithms have been developed using simulated events and optimized and calibrated with B + → J/ψ K + , B 0 →J/ψK* 0 and B 0 →D* − μ + ν μ decay modes with 0.37 fb −1 of data collected in pp collisions at √s = 7 TeV during the 2011 physics run. The opposite-side tagging power is determined in the B + → J/ψ K + channel to be (2.10 ± 0.08 ± 0.24) %, where the first uncertainty is statistical and the second is systematic.Observation of CP violation in B ±→DK ± decays
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 712:3 (2012) 203-212