The CP violating phase β<sup>J/ψφ</sup><sub>s</sub> is measured in decays of B<sup>0</sup><sub>s</sub> → J/ψφ. This measurement uses 5.2 fb<sup>-1</sup> of data collected in √s = 1.96 TeV p‾p collisions at the Fermilab Tevatron with the CDF Run-II detector. CP violation in the B<sup>0</sup><sub>s</sub>-‾B<sup>0</sup><sub>s</sub>bar system is predicted to be very small in the Standard Model. However, several theories beyond the Standard Model allow enhancements to this quantity by heavier, New Physics particles entering second order weak mixing box diagrams. Previous measurements have hinted at a deviation from the Standard Model expectation value for β<sup>J/ψφ</sup><sub>s</sub> with a significance of approximately 2σ. The measurement described in this thesis uses the highest statistics sample available to date in the B<sup>0</sup><sub>s</sub> → J/ψφ decay channel, where J/ψ → μ<sup>+</sup> μ<sup>-</sup> and φ → K<sup>+</sup>K<sup>-</sup>. Furthermore, it contains several improvements over previous analyses, such as enhanced signal selection, fully calibrated particle ID and flavour tagging, and the inclusion of an additional decay component in the likelihood function. The added decay component considers S-wave states of KK pairs in the B<sup>0</sup><sub>s</sub> → J/ψK<sup>+</sup>K<sup>-</sup> channel. The results are presented as 2-dimensional frequentist confidence regions for β<sup>J/ψφ</sup><sub >s</sub> and ΔΓ (the width difference between the B<sup>0</sup><sub>s</sub> mass eigenstates), and as a confidence interval for β<sup>J/ψφ</sup><sub>s</sub> of [0.02,0.52] U [1.08, 1.55] at the 68% confidence level. The measurement of the CP violating phase obtained in this thesis is complemented by the world's most precise measurement of the lifetime τ<sub>s</sub> = 1.53 ± 0.025 (stat.) ± 0.012 (syst.) ps and decay width difference ΔΓ = 0.075 ± 0 .035 (stat.) ± 0.01 (syst.) ps<sup>−1</sup> of the B<sup>0</sup><sub>s</sub> meson, with the assumption of no CP violation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:533839 |
| Date | January 2010 |
| Creators | Oakes, Louise |
| Contributors | Azfar, Farrukh |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:0465d274-fb2f-4b8b-b4f0-d4335fe4520a |
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