Charm Physics in the LHCb Experiment, First Evidence for CP Violation in Charm Decays

摘要

A search for the time integrated CP violation in the D⁰ightarrow h^-h⁺ (h=K,pi ) decays is presented using 0.62 {fb^-1} of data collected by the LHCb experiment in 2011. The flavour of the charm meson is determined by the charge of the slow pion in the D^*+ightarrow D⁰pi ⁺ and the D^*-ightarrow ar {D}⁰pi ^- decays chain. The difference in CP asymmetry between the D⁰ightarrow K^-K⁺ and the D⁰ightarrow pi ^-pi ⁺, Delta A_CPequiv A_CP(K^-K⁺)-A_CP(pi ^-pi ⁺), is measured to be [-0.82±0.21{(stat)}±0.11{(syst)}]%. This differs from the hypothesis of CP conservation by 3.5 standard deviations. An additional search for the time integrated CP violation in the Cabibbo suppressed decay D⁺ightarrow K^-K⁺pi ⁺ is also presented. Here no evidence for CP asymmetry is found using a model independent method. The data used here was collected by the LHCb experiment in 2010 and corresponds to an integrated luminosity of 35 pb^-1. The normalized Dalitz plot distributions for the D⁺ and the D^- are compared using two different binning schemes that are sensitive to different manifestations of CP violation.