Gluon Sivers Function and Single Spin Asymmetry in $e+p^\uparrow \rightarrow e+J/\psi + X$

Abstract

We propose measurement of transverse single spin asymmetry (SSA) in charmonium production as a probe of gluon Sivers function. We estimate SSA in low virtuality electroproduction of $J/\psi $ using color evaporation model of charmonium production and existing models of the gluon Sivers function and find sizable asymmetry at JLab, HERMES, COMPASS and eRHIC energies.