LHCb

Abstract:

A search for CP violation in D^{0}→K^{-}K^{+} and D^{0}→π^{-}π^{+} decays is performed using pp collision data, corresponding to an integrated luminosity of 3  fb^{-1}, collected using the LHCb detector at center-of-mass energies of 7 and 8 TeV. The flavor of the charm meson is inferred from the charge of the pion in D^{*+}→D^{0}π^{+} and D^{*-}→D[over ¯]^{0}π^{-} decays. The difference between the CP asymmetries in D^{0}→K^{-}K^{+} and D^{0}→π^{-}π^{+} decays, ΔA_{CP}≡A_{CP}(K^{-}K^{+})-A_{CP}(π^{-}π^{+}), is measured to be [-0.10±0.08(stat)±0.03(syst)]%. This is the most precise measurement of a time-integrated CP asymmetry in the charm sector from a single experiment.

Abstract:

Within the TORCH (Time Of internally Reflected CHerenkov light) R&D; project, a small-scale TORCH prototype module is currently under study. Circular-shaped micro-channel plate photon detectors with finely segmented square anodes (32 X 32 channels) have been produced for TORCH requirements in industrial partnership. A new generation of custom multi-channel electronics based on the 32-channel NINO and HPTDC ASICs has been developed. The performance of the photon detector coupled to these customized electronics has been assessed in the laboratory and is reported on. A time resolution of 80 ps and a spatial resolution of 0.03 mm have been measured. Finally, tests of the TORCH prototype module illuminated with laser light and in a charged particle beam will be highlighted.

Abstract:

We perform a search for near-threshold Ξb0 resonances decaying to Ξb−π+ in a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. We observe one resonant state, with the following properties: m(Ξ∗0b) − m(Ξ−b) − m(π+) = 15.727 ± 0.068(stat) ± 0.023(syst) MeV/c2 Γ(Ξ∗0b) = 0.90 ± 0.16(stat) ± 0.08(syst) MeV. This confirms the previous observation by the CMS collaboration. The state is consistent with the JP = 3/2+  Ξb∗ 0 resonance expected in the quark model. This is the most precise determination of the mass and the first measurement of the natural width of this state. We have also measured the ratio σ(pp→Ξ∗0bX)B(Ξ∗0b→Ξ−bπ+)/σ(pp → Ξ−bX) =0.28 ± 0.03(stat.) ± 0.01(syst.).

Abstract:

TORCH is a large-area precision time-of-flight detector, based on Cherenkov light production and propagation in a quartz radiator plate, which is read out at its edges. TORCH is proposed for the LHCb experiment at CERN to provide positive particle identification for kaons, and is currently in the Research-and-Development phase. A brief overview of the micro-channel plate photon sensor development, the custom-made electronics, and an introduction to the current test beam activities is given. Optical readout solutions are presented for the potential use of BaBar DIRC bar boxes as part of the TORCH configuration in LHCb.