LHCb is a precision heavy-flavour experiment at the Large Hadron Collider and in 2011 collected just over 1 fb-1 of data at a centre-of-mass energy of √s = 7 TeV. The Ring Imaging Cherenkov (RICH) detectors allow LHCb to identify charged hadrons by measuring their velocity. The system uses Hybrid Photon Detectors to detect rings of single photons emitted by particles travelling through the RICH radiators. The performance-monitoring of these photon detectors whilst data-taking is presented and discussed. LHCb aims to perform precise measurements of Charge-Parity violation in B and D mesons. The final state of B0 → J/Ψ(→μ=μ-)K*(→K=π-) is an admixture of parity-odd and parity-even final states, which are either longitudinally or transversely polarized. These contributions can be separated by performing an angular analysis. The polarization amplitudes and phases of the final state are measured. No difference is observed between the B0 and B0 flavour eigenstates which indicates that Charge-Parity symmetry has been conserved. The ambiguity in the measurement of the strong phase has been resolved by studying the P-wave and S-wave interference in the K/π mass system. The deviation from zero or π in the measurement of the strong phases indicates that final state interactions have occurred. In addition, the prediction that the polarization amplitudes should be similar to those of B0s→ J/Ψo is confirmed.

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Thesis (Ph. D.)--University of Hawaii at Manoa, 2002. / In title the word pi is represented by the Greek symbol. Includes bibliographical references (leaves 104-107). Also available on microfiche.

Decays of B mesons to three-body charmless final states probe the properties of the weak interaction through their dependence on the complex quark couplings in the CKM matrix. They also test dynamical models for hadronic B decays. Based on a sample of 772 million BB pairs collected by the Belle experiment, we present a study of direct CP violation in the decay of charged B to three charged pions. / Ph. D.

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LHCb is a high-precision experiment dedicated to measuring the decays of B hadrons. Particle identification at LHCb relies upon two Ring Imaging Cherenkov (RICH) detectors, and this thesis describes work carried out relating to these detectors. It includes an analysis performed to investigate ion feedback in the Hybrid Photon Detectors (HPDs) used as photosensors for the RICH system, and studies of the performance of a RICH prototype in test beam conditions. A time alignment system for the RICH detectors has been designed and implemented, and this work is presented here. Excellent particle identification performance is required for efficient reconstruction of the b → s penguin decay B0s → ØØ a channel in which visible New Physics effects are possible. An analysis of this decay has been performed, encompassing event selection at trigger and offline levels, resolution, tagging and acceptance studies, and toy monte carlo experiments on sensitivity and systematic errors in measuring the total weak phase. The results are discussed within.

The LHCb experiment (CERN) will offer a precise hadronic probe with which to study CP violation, rare decays and possible New Physics (NP) effects occurring in the b-system. Contained within the vast physics program is a dedicated and intense effort to measure the CP violating weak mixing phase, βs. This phase, observable in the neutral Bs-system, presents a sensitive indicator to NP occurring at the TeV scale. This phase appearing through the theoretically clean ¯b → ¯cc¯s quarklevel transition, can be measured precisely using Bs → J/ψφ decays. The analysis of Bs → J/ψφ decays requires using its decay angular information to separate out the CP eigenstates. The sensitivity to βs can then be extracted from the angular differential rates for this mode. This thesis presents the selection and reconstruction of this decay channel, analysis of the background specific to this channel and the method for fitting the data to extract βs. Previous studies within the collaboration have shown the βs sensitivity using a reduced angular expression for the decay rates. By studying the full angular expression, we find both a quantitative and qualitative improvement in the precision with which βs is obtained: the precision improves by approximately 20%, from ± 0.027 to ± 0.022 radians. In addition, we find it is possible to extract the b-tagging parameter from data itself, which aids to minimise the overall systematic effect. This thesis, in preparation for data taking at the LHCb, presents this expected improvement in measuring βs.

The LHCb experiment at the Large Hadron Collider (LHC) at CERN is designed to make precise measurements of processes including B and D mesons to test the Standard Model (SM) predictions for CP violation, and to search for new physics. From its inception one of the key aims of the LHCb collaboration has been to precisely measure the CP violating phase ϕs, the weak phase due to the interference between B⁰/s -B¯⁰/s mixing and decay. Having collected 3 fb-1 of data in Run 1, the combined results of LHCb measurements of ϕs from various decay modes are in agreement with SM predictions. The aim now is to improve the precision of the LHCb measurement to be sensitive to any small deviation from the SM prediction of ϕs. One strategy to achieve this, in addition to collecting more data, is to expand the number of modes used to measure ϕs to improve the sensitivity of the combination. This thesis presents the measurement of the CP violating phase ϕs in the yet unstudied B⁰/s→ ψ(2S)ϕ decay mode. In addition to providing a measurement of ϕs the study of this mode presents an opportunity to confirm the lifetime difference of the B⁰/s mass eigenstates ∆Γs, currently only measured in the B⁰/s→ Jψϕ decay mode. The results from 3 fb-1 of LHCb data are; ϕs = 0:23+0:29-0:28 ± 0:02 rad, ∆Γs = 0:066+0:041-0:044 ± 0:007 ps-1. which are in agreement with the SM and the results from the LHCb measurement from B⁰/s→ Jψϕ decays.

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, August 1997. / Includes bibliographical references. Also available on the Internet.

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