BACKGAMMON: A Scheme for Compton Backscattered Photoproduction at the International Linear Collider

We propose to investigate the possibility of Compton backscattering low energy laser pulses off the spent electron and positron beams at the International Linear Collider. The hot backscattered photons would then scatter off fixed targets for a rich variety of physics studies in a scheme dubbed BACKGAMMON, for BACKscattered GAMMas On Nucleons. The first objective would be to operate a heavy quark factory, since the cross sections for charm and bottom quark production would be favorable for producing large numbers of these flavors. Secondly, if the incident laser pulses are circularly polarized, the backscattered photons would be circularly polarized as well, allowing the possibility of producing polarized τ pairs on fixed targets. Also, BACKGAMMON’s polarized hot photons could scatter off polarized targets and play an important role in elucidating the spin structure of nucleons. Finally, there is the possibility of studying the photon structure function for the spent electron beam scattering off laser photons.