Abstract:

The decay B̄s0→J/ψK +K - is investigated using 0.16fb -1 of data collected with the LHCb detector using 7 TeV pp collisions. Although the J/ψ channel is well known, final states at higher K +K - masses have not previously been studied. In the K +K - mass spectrum we observe a significant signal in the f2′(1525) region as well as a nonresonant component. After subtracting the nonresonant component, we find B(B̄s0→J/ψf2′(1525))/ B(B̄s0→J/ψ)=(26.4±2.7±2.4)%. © 2012 CERN.

Abstract:

Charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of √S = 7 TeV in different intervals of pseudorapidity η. Charged particles are reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the η ranges -2.5<η<-2.0 and 2.0<η<4.5. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/c a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of η. In general, the models underestimate charged particle production. © 2012 CERN for the benefit of the LHCb collaboration.

Abstract:

Charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of √S = 7 TeV in different intervals of pseudorapidity η. Charged particles are reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the η ranges -2.5<η<-2.0 and 2.0<η<4.5. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/c a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of η. In general, the models underestimate charged particle production. © 2012 CERN for the benefit of the LHCb collaboration.

Abstract:

The B s0-B -s0 oscillation frequency δm s is measured with 36 pb -1 of data collected in pp collisions at s=7TeV by the LHCb experiment at the Large Hadron Collider. A total of 1381 B s0→D s-π+ and B s0→D s-π +π -π + signal decays are reconstructed, with average decay time resolutions of 44 fs and 36 fs, respectively. An oscillation signal with a statistical significance of 4.6σ is observed. The measured oscillation frequency is δm s=17.63±0.11(stat)±0.02(syst)ps -1. © 2012 CERN.