Search for D0--anti-D0 Mixing and Branching-Ratio Measurement in the Decay D0 --> K+ pi- pi0

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--anti-D0 mixing using regions of phase space in the decay D0 --> K+ pi- pi0. We measure the time-integrated mixing rate R_M = (0.023 +0.018/-0.014(stat.) +/- 0.004(syst.))%, and R_M < 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+ pi- pi0 relative to D0 --> K- pi+ pi0 to be (0.214 +/- 0.008(stat.) +/- 0.008(syst.))%.