Small x gluon from exclusive J/ψ production

Exclusive J/psi production, gamma* p -> J/psi p, offers a unique opportunity to determine the gluon density of the proton in the small x domain. We use the available HERA data to determine the gluon distribution in the region 10(-4) less than or similar to x less than or similar to 10(-2) and 2 less than or similar to Q(2) less than or similar to 10 GeV2, where the uncertainty on the gluon extracted from the global parton analyses is large. The gluon density is found to be approximately flat at the lower scale; it is compared with those of recent global analyses. (C) 2008 Elsevier B.V. All rights reserved.