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: $D^0 \to K^-π^+$ and $D^0 \to K^-K^+$. This translates into a measurement of the $y_{CP}$ mixing parameter in the $\d0d0$ 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 a CP violating asymmetry in the Cabibbo suppressed decay modes $D^+ \to K^-K^+π^+$, $D^0 \to K^-K^+$ and $D^0 \to π^-π^+$. We show preliminary results on a measurement of the branching ratio $Γ(D^{*+}\to π^+ (K^+π^-))/Γ(D^{*+}\to π^+ (K^-π^+))$.