A method to include exclusive heavy vector-meson production data at small x in global parton analyses

We propose a method which allows the inclusion of exclusive heavy vector-meson production data at low <i>x</i> in future global parton analyses. As an example we perform a study within xFitter to determine the gluon parton distribution function (PDF) at next-to-leading order (NLO) at moderate-to-low <i>x</i> using the measurements of exclusive <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>J</mml:mi> <mml:mo>/</mml:mo> <mml:mi>ψ</mml:mi></mml:mrow> </mml:math> production in <i>ep</i> and <i>pp</i> collisions from HERA and LHC. We further study the constraints from the corresponding <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Υ</mml:mi></mml:math> production process. We finish by discussing the possible effects at next-to-next-to-leading order (NNLO) through incorporation of a <i>K</i> factor for the exclusive heavy vector-meson coefficient function at NLO.