We report the first observation of diffractive J/psi(-> mu+
mu-) production in p anti-p collisions at s**(1/2) = 1.8 TeV. Diffractive
events are identified by their rapidity gap signature. In a sample of
events with two muons of transverse momentum pmu_T > 2 GeV/c within the
pseudorapidity region |eta| < 1.0, the ratio of diffractive to total J/psi
production rates is found to be R_j/psi = [1.45 +/- 0.25]%. The ratio
R_j/psi(x) is presented as a function of x-Bjorken. By combining it with
our previously measured corresponding ratio R_jj(x) for diffractive dijet
production, we extract a value of 0.59 +/- 0.15 for the gluon fraction of
the diffractive structure function of the proton.
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Updated: Tuesday, 2002 January 08 15:45:29 CST automatically from input from Carol Picciolo