Relativistic corrections to photoproduction of J/#psi#

We consider various models for photoproduction of J/#psi# on protons, based on the well-known photon-gluon fusion mechanism. We show that relativistic corrections to the J/#psi# bound state lead to a better description of the EMC and NMC data, especially in the high z region (z > 0.8) where the naive (nonrelativistic) colour singlet model breaks down (z is E_J_/_#psi#/E_#gamma# in the proton rest frame). As most of the events are expected in this domain, these corrections are important for extracting the gluon distribution function from the data. We also discuss diffractive J/#psi# production and a heuristic model for elastic production. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(93-072) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Double J/#psi# production: a probe of gluon polarization?

We consider the process of direct simultaneous production of two J/#psi# particles and discuss the possibility that it can be used as a tool to measure the gluon polarization in the colliding particles. (orig.)Available from TIB Hannover: RA 2999(93-048) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Gluon extraction from charm and bottom production at LEP/LHC

SIGLETIB: RA 2999(90-160) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman