Threshold Upsilon-meson Photoproduction at EIC and EicC

Abstract

High-accuracy ${\rm Y}$-meson photoproduction data from EIC and EicC experiments will allow the measurement of the near-threshold total cross section of the reaction $\gamma p\to {\rm Y}p$, from which the absolute value of the ${\rm Y}p$ scattering length, $|{\alpha }_{{\rm Y}p}|$, can be extracted using a Vector-Meson Dominance model. For this evaluation, we used ${\rm Y}$-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 $|{\alpha }_{{\rm Y}p}|$ with the recently determined scattering lengths for $\omega p$, $\varphi p$, and $J/\psi p$ using the A2, CLAS, and GlueX experimental data are performed. The role of the "young" vector-meson effect is evaluated.

Comments: 6 pages, 6 figures, 3 tables