SEARCH FOR THE DECAY D0[-MU+MU-

Using a silicon-microstrip detector array to identify secondary vertic es occurring downstream of a short platinum target, we have searched f or the decay D0-->mu+mu-. Normalized relative to the j/psi-->mu+mu- si gnal observed in the same data sample, for a 3.25-mm minimum decay dis tance our branching-ratio sensitivity is (4.8 +/- 1.4)X 10(-6) per eve nt, and after background subtraction we observe -4.1 +/- 4.8 events. U sing the statistical approach advocated by the Particle Data Group, we obtain a limit B(D0-->mu+mu-)<3.1 X 10(-5) at 90% confidence, confirm ing with a different technique the limit previously obtained by Louis et al. The interpretation of the upper limit involves complex statisti cal issues; we present another approach which is more suitable for com bining the results of different experiments.