Schrodinger handbag model

The excitation of a nonrelativistic composite system, by a weakly interacting probe, is considered in the style of the properly covariant parton model. It is hoped in particular thereby to illuminated the handbag approximation. It is found that even for a confining potential such an approximation can sensibly be defined, and then describes correctly the poorly resolved deep inelastic scattering. The approximation is significantly improved (subasymptotically) by the suppression of the off-mass-shell displacement of the initial parton. (5 refs).