Charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of square root 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 1GeV/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.
A search for the decays Bs-->mumu and Bd-->mumu is performed with about 37 pb^{-1} of pp collisions at sqrt{s} = 7 TeV collected by the LHCb experiment at the Large Hadron Collider at CERN. The ...observed numbers of events are consistent with the background expectations. The resulting upper limits on the branching ratios are BR(Bs-->mumu) < 5.6 x 10^{-8} and BR(Bd-->mumu) <1.5 x 10^{-8} at 95% confidence level.
The production of K_short mesons in pp collisions at a centre-of-mass energy of 0.9 TeV is studied with the LHCb detector at the Large Hadron Collider. The luminosity of the analysed sample is ...determined using a novel technique, involving measurements of the beam currents, sizes and positions, and is found to be 6.8 +/- 1.0 microbarn^-1. The differential prompt K_short production cross-section is measured as a function of the K_short transverse momentum and rapidity in the region 0 < pT < 1.6 GeV/c and 2.5 < y < 4.0. The data are found to be in reasonable agreement with previous measurements and generator expectations.
We report on tests of a novel ring imaging Cherenkov (RICH) detection system consisting of a 3-m-long gaseous
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radiator, a focusing mirror, and a photon detector array based on Hamamatsu ...multi-anode photomultiplier tubes. This system was developed to identify charged particles in the momentum range from 3 to 70
GeV/c for the BTeV experiment.
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