Near threshold $J/\psi$ and ${\rm Y}$ photo-production at JLab and RHIC

Abstract

We update our previous calculation of $J/\psi$ photo-production near threshold \cite{Hatta:2018ina} by incorporating the recent developments in theory and the new experimental data from the GlueX collaboration at Jefferson Lab \cite{Ali:2019lzf}. We then propose to study the near threshold production of ${\rm Y}$ and $J/\psi$ in ultraperipheral $pA$ collisions at RHIC. These processes are sensitive to the gluon condensate in the proton which is related to the QCD trace anomaly. Our result emphasizes the role of gluons as the origin of the proton mass.

Comments: 10 pages, 9 figures