Two-gluon form factor of the nucleon and $J/\psi$ photoproduction

Abstract

We argue that the t-dependence of the two-gluon form factor of the nucleon should be given by $\Gamma(t)=(1-t/m_{2g}^2)^{-2}$ with $m_{2g}^2\approx 1 GeV^2$. We demonstrate that this form provides a good description of the t-dependence of the cross section of the elastic photoproduction of $J/\psi$-mesons between the threshold region of $E_{\gamma}=11 GeV$ (Cornell), $E_{\gamma}=19 GeV$ (SLAC) and $E_{\gamma}=100 GeV$ (FNAL) including the strong energy dependence of the t-slope. It is also well matched with the recent HERA data. The same assumption explains also the t-dependence of $\phi$-meson electroproduction near threshold at $W=2.3 GeV, Q^2=1.0 GeV^2$.