Very low $x$ gluon density determined by LHCb exclusive $J/\psi$ data

Chris A. Flett, Alan D. Martin, Misha G. Ryskin +1

The low $x$ behaviour of the gluon density $xg(x,{\mu }^2)$ at scale ${\mu }^2=2.4$ GeV${}^2$ is determined using exclusive $J/\psi$ production data from HERA and LHCb within the framework of col…