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 B and B mixing frequencies, Δm and Δm , are measured using a data sample corresponding to an integrated luminosity of 1.0 fb collected by the LHCb experiment in pp collisions at a centre of mass energy of 7 TeV during 2011. Around 1.8 × 10 candidate events are selected of the type B → D μ (+ anything), where about half are from peaking and combinatorial backgrounds. To determine the B decay times, a correction is required for the momentum carried by missing particles, which is performed using a simulation-based statistical method. Associated production of muons or mesons allows us to tag the initialstate flavour and so to resolve oscillations due to mixing. We obtain Δm = (17.93 ± 0.22 (stat) ± 0.15 (syst)) ps , Δm = (0.503 ± 0.011 (stat) ± 0.013(syst)) ps . The hypothesis of no oscillations is rejected by the equivalent of 5.8 standard deviations for B and 13.0 standard deviations for B . This is the first observation of B mixing to be made using only semileptonic decays. 0 0 −1 6 0 − + −1 −1 0 0 0 s s d (s) (s) s d s s

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 of pp collisions delivered by the LHC at √s = 0.9 TeV and 1.8 nb at √s = 7 TeV. The measurements are performed as a function of transverse momentum p 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 ≡ y − y, and is used to constrain models of baryon transport. − + − + + − + − + − + − −1 −1 T beam