Probes of the small x gluon via exclusive J/ψ and Υ production at HERA and the LHC

New, more precise data on diffractive J/psi photoproduction and on exclusive J/psi production in the process pp -> p + J/psi + p at the LHC allow a better constraint on the low-x gluon distribution in the domain of relatively low scales Q(2) similar to 2 - 6GeV(2). We account for the 'skewed' effect and for the real part of the amplitude, as well as for the absorptive corrections in the case of the exclusive process pp -> p+J/psi+p. The predictions for exclusive J/psi production at root s = 8 and 14 TeV and for exclusive Upsilon(1S) production at 7, 8 and 14 TeV are also given. We present results at leading and next-to-leading order.