CHARMONIUM PRODUCTION VIA FRAGMENTATION AT DESY HERA

The cross section for the photoproduction of large-p(T) J/psi mesons a t DESY HERA is calculated at next-to-leading order. adopting a perturb ative approach to describe the fragmentation of charm quarks and gluon s into J/psi mesons. We treat the charm quark according to the massles s factorization scheme, where it is assumed to be one of the active fl avors inside the proton and the resolved photon. We present inclusive distributions in transverse momentum and rapidity, including the contr ibutions due to direct and resolved photons. The importance of the col or-octet components of the J/psi wave function, which contribute to th e fragmentation process, is emphasized. In addition to prompt J/psi pr oduction, we consider also the production of chi(cJ) states followed b y radiative decays to J/psi mesons, both in the color-singlet and colo r-octet channels.