We compare the cross section for exclusive J/ψ photoproduction calculated at NLO in the collinear factorization approach with HERA and LHCb data. Using the optimum scale formalism together with the subtraction of the low kt<Q0 contribution from the NLO coefficient function to avoid double counting we show that the existing global parton distribution functions (PDFs) are consistent with the data within their uncertainties. However, at low x the uncertainties of the present global PDFs are large. On the other hand, the accuracy of the LHCb data are rather good. Therefore, these data provide the possibility to directly measure the gluon PDF over the very large interval of x, 10−6<x<10−2, at a fixed low scale.
@article{arxiv.1908.08398,
title = {How to include exclusive $J/\psi$ production data in global PDF analyses},
author = {Chris A. Flett and Stephen P. Jones and Alan D. Martin and Misha G. Ryskin and Thomas Teubner},
journal= {arXiv preprint arXiv:1908.08398},
year = {2020}
}
Comments
16 pages, 6 figures, text improved, references added