Research Papers in Physics and Astronomy


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Published by American Physical Society. PPhys. Rev. Lett. 87, 241802 (2001). Copyright © 2001 American Physical Society. Permission to use.


We report the first observation of diffractive J/ψ(→μ+μ-) production in p̅p collisions at √s= 1.8 TeV. Diffractive events are identified by their rapidity gap signature. In a sample of events with two muons of transverse momentum pT,/sub> μ> 2 GeV/c within the pseudorapidity region |η| J/ψ production rates is found to be RJ=[1.45 ± 0.25]%. The ratio RJ(x) is presented as a function of x-Bjorken. By combining it with our previously measured corresponding ratio Rjj(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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