Search for D0-D¯0 Mixing and Branching-Ratio Measurement in the Decay D0→K+π-π0

We analyze 230.4  fb-1 of data collected with the BABAR detector at the PEP-II e+e- collider at SLAC to search for evidence of D0-D̅ 0 mixing using regions of phase space in the decay D0→K+π-π0. We measure the time-integrated mixing rate RM=(0.023-0.014+0.018(stat.)±0.004(syst.))%, and RM<0.054% at the 95% confidence level, assuming CP invariance. The data are consistent with no mixing at the 4.5% confidence level. We also measure the branching ratio for D0→K+π-π0 relative to D0→K-π+π0 to be (0.214±0.008(stat.)±0.008(syst.))%.