XYZ spectroscopy at electron-hadron facilities: Exclusive processes

Abstract

The next generation of electron-hadron facilities has the potential for significantly improving our understanding of exotic hadrons. The X Y Z states have not been seen in photon-induced reactions so far. Their observation in such processes would provide an independent confirmation of their existence and offer new insights into their internal structure. Based on the known experimental data and the well-established quarkonium and Regge phenomenology, we give estimates for the exclusive cross sections of several X Y Z states. For energies near threshold we expect cross sections of few nanobarns for the Z c ( 3900 ) + and upwards of tens of nanobarns for the X ( 3872 ) , which are well within reach of new facilities.