Abstract:

The CP asymmetry in the mixing of B0s and B¯0s mesons is measured in proton-proton collision data corresponding to an integrated luminosity of 3.0 fb−1, recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV. Semileptonic B0s and B¯0s decays are studied in the inclusive mode D∓s μ± ν-μX with the D∓s mesons reconstructed in the K+K−π∓ final state. Correcting the observed charge asymmetry for detection and background effects, the CP asymmetry is found to be assl=(0.39 ± 0.26 ± 0.20)%, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of assl to date. It is consistent with the prediction from the standard model and will constrain new models of particle physics.

Abstract:

The data sample of Λb0 → J/ψpK- decays acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3  fb^-1, is inspected for the presence of J/ψp or J/ψK- contributions with minimal assumptions about K-p contributions. It is demonstrated at more than nine standard deviations that Λ0b → J/ψpK- decays cannot be described with K-p contributions alone, and that J/ψp contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for P+c → J/ψp charmonium-pentaquark states in the same data sample.

Abstract:

Associated production of bottomonia and open charm hadrons in pp collisions at s=7 and 8 TeV is observed using data corresponding to an integrated luminosity of 3 fb−1 accumulated with the LHCb detector. The observation of five combinations, Y(1S)D0, Y(2S)D0, Y(1S)D+, Y(2S)D+ and Y(1S)Ds+, is reported. Production crosssections are measured for Y(1S)D0 and Y(1S)D+ pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism.

Abstract:

© 2015 The Authors. The TORCH time-of-flight detector is being developed to provide particle identification between 2 and 10 GeV/c momentum over a flight distance of 10 m. TORCH is designed for large-area coverage, up to 30 m2, and has a DIRC-like construction. The goal is to achieve a 15 ps time-of-flight resolution per incident particle by combining arrival times from multiple Cherenkov photons produced within quartz radiator plates of 10 mm thickness. A four-year R&D programme is underway with an industrial partner (Photek, UK) to produce 53×53 mm2 Micro-Channel Plate (MCP) detectors for the TORCH application. The MCP-PMT will provide a timing accuracy of 40 ps per photon and it will have a lifetime of up to at least 5 Ccm-2 of integrated anode charge by utilizing an Atomic Layer Deposition (ALD) coating. The MCP will be read out using charge division with customised electronics incorporating the NINO chipset. Laboratory results on prototype MCPs are presented. The construction of a prototype TORCH module and its simulated performance are also described.

Abstract:

The oscillation frequency, Δ md, of B0 mesons is measured using semileptonic decays with a D- or D∗- meson in the final state. The data sample corresponds to 3.0fb-1 of pp collisions, collected by the LHCb experiment at centre-of-mass energies √s = 7 and 8 TeV. A combination of the two decay modes gives Δmd = (505.0 ± 2.1 ± 1.0) ns-1, where the first uncertainty is statistical and the second is systematic. This is the most precise single measurement of this parameter. It is consistent with the current world average and has similar precision.