Measurements of Indirect CP Violation in Charm at LHCb

UoM administered thesis: Phd

  • Authors:
  • Mark Smith


This thesis describes two pieces of work. The first is a study of the resolution of the LHCb vertex locator throughout Run 1. The second comprises analyses to measure the charm mixing and CP violation observables A_{Gamma} and y_{CP}.An estimate of the resolution of the LHCb vertex locator is required for use in the track fits. A method to measure the resolution with collision data has been developed and tested. The performance of the sub-detector throughout Run 1 of the LHC has been assessed. A significant degrading of the resolution has been seen. The effects of this on the track reconstruction has been examined with little change in the measured quantities being observed.The measurement of indirect CP violation in neutral D meson transitions has been measured through the observables A_{Gamma} and y_{CP}, using 1fb^{-1} of pp collisions with a centre of mass energy 7TeV, collected by the LHCb detector in 2011.A_{Gamma} describes the CP asymmetry of the lifetime of the D^0 decaying to a CP eigenstate (KK or pipi). The analysis documented here yields A_{Gamma} = (-0.17+-0.54)x10^{-3} when the measurements are combined. This is the world's best measurement and represented a factor of four improvement over the previous best result.The observable y_{CP} compares the effective lifetimes of the Cabibbo favoured decay D^0->Kpi and the transition to a CP eigenstate (KK or pipi). The unblinded result obtained in this document, averaged over both final states is y_{CP} = (5.61+-1.56)x10^{-3}. This result is commensurate with the world average central value within 1.25 standard deviations and has significance of 3.6 standard deviations relative to zero.


Original languageEnglish
Awarding Institution
Award date1 Aug 2016