J/psi plus jet diffractive production in the direct photon process at HERA

We present a study of the J/psi + jet diffractive production in direct phot on processes at HERA based on the factorization theorem for lepton-induced hard diffractive scattering and the factorization formalism of the non-rela tivistic QCD (NRQCD) for quarkonia production. Using the diffractive gluon distribution function extracted from HERA data on diffractive deep inelasti c scattering and diffractive dijet photon production, we demonstrate that t his process is measurable at DESY HERA. The experimental study of this proc ess can give valuable insight in the diffractive production mechanism and t est the color-octet mechanism for heavy quarkonia production in a new envir onment.