Associated J/psi+gamma production through double pomeron exchange: the nature of the pomeron and hard diffractive factorization breaking

We present a study of associated J/psi + gamma production through double po meron exchange at energies reached st the Fermilab Tevatron and CERN LHC ba sed on the Ingelman-Schlein model for hard diffractive scattering and the f actorization formalism of nonrelativistic QCD for quarkonia production. We find that the process p + (p) over bar --> p + (p) over bar + J/psi + gamma + X can be used to probe the gluon content of the pomeron and study the na ture of hard diffractive factorization breaking.