Exclusive J/psi and Upsilon photoproduction and the low x gluon
  We discuss the potential to constrain the small-$x$ PDFs using the exclusive production of heavy vector mesons. The calculation of $J/\psi$ and $\Upsilon$ photoproduction at NLO in collinear factorisation is described. The different behaviour of the NLO corrections for $J/\psi$ and $\Upsilon$ is highlighted and we outline what might be expected from the inclusion of these processes in a PDF fit. 
S. P. Jones, A. D. Martin, M. G. Ryskin and T. Teubner
hep-ph