Analysis of D0 -> K+ pi- pi0 Decays: Search for D0-D0bar Mixing, and Measurements of the Doubly Cabibbo-Suppressed Decay Rate and Resonance Contributions

Analyzing D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} decays, herein are presented the methods and results of a search for D{sup 0}-{bar D}{sup 0} mixing, a measurement of the branching ratio R {equivalent_to} {Lambda}(D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0})/{Lambda}(D{sup 0} {yields} K{sup -}{pi}{sup +}{pi}{sup 0}), and measurements of the contributions from D{sup 0} {yields} K{sup +}{rho}{sup -}, K*{sup +}{pi}{sup -}, K*{sup 0}{pi}{sup 0}; 230.4 fb{sup -1} of data collected from the BABAR detector at the PEP-II collider during 2000-2004 (Runs 1-4) are analyzed. An event-level tagging technique is developed, which facilitates the accurate determination of doubly Cabibbo-suppressed resonance contributions by suppressing background from Cabibbo-favored decays. The branching ratio is measured as R = (0.214 {+-} 0.008 (stat) {+-} 0.008 (syst))%, with (46.1 {+-} 3.3 (stat) {+-} 2.9 (syst))% of D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} decays proceeding through the channel D{sup 0} {yields} K*{sup +}{pi}{sup -}. The data are consistent with the null-D-mixing hypothesis at a confidence level of 10%, and the expected value of {+-} {radical}(x{sup 2} + y{sup 2}) is measured as -0.013 {+-} 0.010 (stat), indicating negative interference between mixing and doubly Cabibbo-suppressed decay. The expected value of the integrated mixing rate is (x{sup 2} + y{sup 2})/2 = (0.013 {+-} 0.013 (stat))%