Threshold Upsilon-meson Photoproduction at EIC and EicC

High-accuracy Upsilon-meson photoproduction data from the EIC and EicC experiments will allow measurement of the near-threshold total cross section of the reaction gpàUpsilon p, from which the absolute value of the Upsilon p scattering length, |alpha(Upsilon p)|, can be extracted using a VMD model. For this evaluation, we used Upsilon-meson photoproduction quasi-data from the QCD approach (the production amplitude can be factorized in terms of gluonic generalized parton distributions and the quarkonium distribution amplitude). A comparative analysis of |alpha(Upsilon p)|$ with the recently determined scattering lengths for omega-p, phi-P, and J/psi-P using the A2, CLAS, and GlueX experimental data are performed. The role of the ``young'' vector-meson effect is evaluated.