The gluonic radii of light nuclei; A threshold coherent electroproduction measurement of upsilon at and EIC

The fully exclusive elastic electroproduction of $\Upsilon$ on the proton, deuteron, $^3$He and $^4$He at an EIC is a powerful tool to extract their gluonic radii and examine the contribution of the trace anomaly to their mass. Only at energies and luminosity planned for a future US-based EIC that one can contemplate these challenging measurements to reach these goals. The full exclusivity of the process as well as the access of large $Q^2$ and low $t$ in the threshold region should allow to address both the reaction mechanism of electroproduction of $\Upsilon$ as well as the multiple gluonic exchange between the probe and the target in a region of virtual-photon target invariant mass ranging from a perturbative to a non-perturbative regime. We will discuss the motivation of such measurements and show projections of achievable precision in the determination of these gluonic radii using the TOPSiDE detector concept.