New FOCUS results on charm mixing and CP violation

Abstract

We present a summary of recent results on CP violation and mixing in the charm quark sector based on a high-statistics sample collected by photoproduction experiment FOCUS (E831 at Fermilab). We have measured the difference in lifetimes for the D 0 decays: D 0 → K −π + and D 0 → K − K +. This translates into a measurement of the y CP mixing parameter in the D 0 D 0 system, under the assumptions that K − K + is an equal mixture of CP odd and CP even eigenstates, and CP violation is negligible in the neutral charm meson system. We verified the latter assumption by searching for CP violating asymmetry in the Cabibbo suppressed decay modes D + → K − K +π +, D 0 → K − K + and D 0 → π −π +. We report preliminary results on a measurement of the branching ratio Γ( D *+ → π +( K +π −))/Γ( D *+ → π +( K −π +)).