Two cue validity models for category learning were compared to the exemplar model of Medin & Schaffer (1978). The cue validity models tested for the use of two cue validity measures from the Competition Model of Bates & MacWhinney (1982, 1987, 1989) ("reUabiUty" and "overall validity"); one of these models additionally tested for "rote" associations between items and categories. Twenty-four undergraduate subjects learned to classify pseudowords into two categories over 40 blocks of trials. The overall fit of the cue validity model without rote associations was poor, but the fit of the model that included these was nearly identical to the exemplar model {R^ = .89 V3 .90). However, both cue validity models failed to capture differences predicted by exemplar similarity, but not cue validity, that were apparent as early as the first block of learning trials. The critical parameters in the Medin-SchaiFer model were fit as a logarithmic function of the learning block to provide a uniform account of learning across the 40 blocks of trials. The evidence that we provide suggests that competition at the level of exemplars should be considered as a possible extension of the Competition Model.

The relative rates of B-meson decays into J/ψ and ψ(2S) mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions ([Formula: see text]) are measured to be [Formula: see text] where the third uncertainty is from the ratio of the ψ(2S) and J/ψ branching fractions to μ⁺μ^-.

The production of J/ψ mesons in proton-proton collisions at √S = 7 TeV is studied with the LHCb detector at the LHC. The differential cross-section for prompt J/ψ production is measured as a function of the J/ψ transverse momentum pT and rapidity y in the fiducial region pT ∈ [0; 14] GeV/c and y ∈ [2.0; 4.5]. The differential cross-section and fraction of J/ψ from b-hadron decays are also measured in the same pT and y ranges. The analysis is based on a data sample corresponding to an integrated luminosity of 5.2 pb^&-1. The measured cross-sections integrated over the fiducial region are 10.52 ± 0.04 ± 1.40^+1.64 &-2.20 μb for prompt J/ψ production and 1.14 ± 0.01 ± 0.16 μb for J/ψ from b-hadron decays, where the first uncertainty is statistical and the second systematic. The prompt J/ψ production cross-section is obtained assuming no J/ψ polarisation and the third error indicates the acceptance uncertainty due to this assumption.

The B s0→J/ψK S0 branching fraction is measured in a data sample corresponding to 0.41fb -1 of integrated luminosity collected with the LHCb detector at the LHC. This channel is sensitive to the penguin contributions affecting the sin2β measurement from B 0→J/ψK S0. The time-integrated branching fraction is measured to be B(B S0→J/ψK S0)=(1.83±0.28)×10 -5. This is the most precise measurement to date. © 2012 CERN.

The charged−particle production ratios p/p, K −/K +, π −/π +, (p + p)/(π ++π −), (K ++K −)/(π + + π −) and (p+ p)/(K + + K −) are measured with the LHCb detector using 0.3 nb−1 of pp collisions delivered by the LHC at √s = 0.9 TeV and 1.8 nb−1 at √s = 7 TeV. The measurements are performed as a function of transverse momentum pT and pseudorapidity η. The production ratios are compared to the predictions of several Monte Carlo generator settings, none of which are able to describe adequately all observables. The ratio p/p is also considered as a function of rapidity loss, Δy ≡ ybeam − y, and is used to constrain models of baryon transport.

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.

The calibration and performance of the opposite-side 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/ψK⁺, B⁰→J/ψK^∗0 and B⁰→D^∗-μ⁺ν_μ decay modes with 0.37 fb^-1 of data collected in pp collisions at [Formula: see text] during the 2011 physics run. The opposite-side tagging power is determined in the B⁺→J/ψK⁺ channel to be (2.10±0.08±0.24) %, where the first uncertainty is statistical and the second is systematic.