Search for D0-D¯0 Mixing and a Measurement of the Doubly Cabibbo-Suppressed Decay Rate in D0→Kπ Decays

We present results of a search for D⁰-D¯⁰ mixing and a measurement of R_D, the ratio of doubly Cabibbo-suppressed decays to Cabibbo-favored decays, using D⁰→K⁺π^- decays from 57.1 fb^-1 of data collected near (s)=10.6 GeV with the BABAR detector at the PEP-II collider. At the 95% confidence level, allowing for CP violation, we find the mixing parameters x^'2<0.0022 and -0.056<y'<0.039, and the mixing rate R_M<0.16%. In the limit of no mixing, R_D=[0.357±0.022(stat)±0.027(syst)]% and the CP-violating asymmetry A_D=0.095±0.061(stat)±0.083(syst).