Measurement of the doubly Cabibbo suppressed decay D0→K+π− and a search for charm mixing

We present an analysis of the decay D0→K+π− based on FOCUS data. From a sample of 234 signal events, we find a branching ratio of Γ(D0→K+π−)Γ(D0→K−π+)=(0.429−0.061+0.063±0.027)% under the assumptions of no mixing and no CP violation. Allowing for CP violation, we find a branching ratio of (0.429±0.063±0.028)% and a CP asymmetry of 0.18±0.14±0.04. The branching ratio for the case of mixing with no CP violation is (0.381−0.163+0.167±0.092)%. We also present limits on charm mixing.