Determination of the wrong sign decay rate D 0 → K + π − and the sensitivity to D 0 −

The D0 meson can decay to the wrong sign K+ π state either through a doubly Cabibbo suppressed decay or via mixing to the D0 state followed by the Cabibbo favoured decay D0 → K+π−. We measure the rate of wrong sign decays relative to the Cabibbo favoured decay to (0.383 ± 0.044 ± 0.022)% and give our sensitivity to a mixing signal. Contributed to the Proceedings of the International Europhysics Conference on HEP, 12—18 July 2001, Budapest, Hungary Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309 Work supported in part by Department of Energy contract DE-AC03-76SF00515.