Measurement of the CP violating phase ϕs using B⁰/s → ψ(2S)ϕ decays at the LHCb Experiment
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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.