Parton Model and Inelastic Processes with Two Photons

It is proposed that highly inelastic hadronic reactions involving two photons (Compton scattering, photoproduction of low-mass $\mu$ pairs, hadron-hadron $\gamma$-pair production, etc.) be studied to distinguish between two approaches to the parton model: the direct impulse approximation of Bjorken and Paschos, and the field-theoretic method of Drell, Levy, and Yan. Such a distinction may be possible since a field-theoretic justification of the free-parton approximation in such processes cannot be given except in a limited kinematic region.