Search for the decay D0+-

Using a silicon-microstrip detector array to identify secondary vertices occurring downstream of a short platinum target, we have searched for the decay D0+-. Normalized relative to the J/+- signal observed in the same data sample, for a 3.25-mm minimum decay distance our branching-ratio sensitivity is (4.81.4)×10-6 per event, and after background subtraction we observe -4.14.8 events. Using the statistical approach advocated by the Particle Data Group, we obtain a limit B(D0+-)<3.1×10-5 at 90% confidence, confirming with a different technique the limit previously obtained by Louis et al. The interpretation of the upper limit involves complex statistical issues; we present another approach which is more suitable for combining the results of different experiments.