Observation of CP violation in B+/- → DK+/- decays

Description

An accurate determination of the angle γ of the Unitary Triangle is one of the most important goals of the LHCb experiment. The LHCb detector is a single-arm spectrometer at the LHC, optimised for beauty and charm flavour physics. As the angle γ is the least experimentally constrained parameter of the Unitary Triangle, its precise experimental determination can be used to test the validity of the Standard Model. The Unitary Triangle phase γ can be extracted in B → DK decays at tree-level, exploiting the interference between b → c(ūs) and b → u(c̄s) transitions. This interference is sensitive to γ and can give measurable charge asymmetries. In particular, γ ≠ 0 is required to produce direct CP violation in B decays and this is the only CP-violating mechanism for the decay of charged B^± mesons. In this thesis, an analysis of CP violation in B^± → DK^± and B^± → Dπ^± decays is presented, where the D meson is reconstructed in the two-body final states: K^±π^∓, K⁺K⁻, π⁺π⁻ and π^±K^∓. The analysis uses the full 2011 LHCb dataset of 1.0 fb^-1, collected from pp collisions at √s = 7 TeV. Several CP-related quantities, e.g the ratio of B → DK and B → Dπ branching fractions and their charge asymmetries, are measured via a simultaneous fit to the invariant mass distributions of the modes considered. The suppressed B^± → DK^± mode is observed for the first time with ≈ 10σ significance. Once all measurements are combined, direct CP violation is established in B^± decays with a total significance of 5.8σ.

Links & Downloads

1. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581125

Tags

539.73

Additional Fields

Identifer	oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:581125
Date	January 2012
Creators	Gandini, Paolo
Contributors	John, Malcolm
Publisher	University of Oxford
Source Sets	Ethos UK
Detected Language	English
Type	Electronic Thesis or Dissertation
Source	http://ora.ox.ac.uk/objects/uuid:b6db99c0-7b46-45af-8e7c-6b6fddd73abb