Exclusive vector meson production at an electron-ion collider

Coherent exclusive vector meson electroproduction is a key physics channel at an electron-ion collider. It probes the gluon structure of nuclei over a wide range of Q², and can be used to measure nuclear shadowing and to search for gluon saturation and/or the colored glass condensate. In this paper, we present calculations of the kinematic distributions for a variety of exclusive vector meson final states: the ρ , ϕ , J /ψ , ψ^', and the Υ states. The cross sections for light and c c ¯ mesons are large, while Υ states should be produced in moderate numbers at a medium energy electron-ion collider (EIC)—i.e., one corresponding to the proposed U.S. designs—and in large numbers at the CERN Large Hadron Electron Collider (LHeC). We investigate the acceptances for these states, as a function of detector rapidity coverage. A large-acceptance detector is needed to cover the full range photon-nucleon collision energies produced at an EIC; a forward detector is required to observe vector mesons from the most energetic photon interactions, and thereby probe gluons at the lowest possible Bjorken-x values.