J/$psi$p Scattering Length from GlueX Threshold Measurements

The quality of the recent GlueX $J/psi $ photoproduction data from Hall~D at Jefferson Laboratory, and the proximity of the data to the energy threshold, gives access to a variety of interesting physics aspects. As an example, an estimation of the $J/psi$-nucleon scattering length $alpha_{J/psi p}$ is provided within the vector meson dominance model. It results in $|alpha_{J/psi p}| = (3.08pm 0.55 ({rm stat.}) pm 0.45 ({rm syst.}))$~mfm.