Coincidence Electroproduction and Scaling in the Regge Region

We consider the coincidence electroproduction process $l+p\to l^{\prime }+p^{\prime }+\mathrm{anything}$. With the momentum transfer between $p$ and $p^{\prime }$ held fixed, a single trajectory in the $p{\overline{p}}^{\prime }$ channel dominates as the laboratory energy of the virtual photon becomes large. (It is known that the onset of single-trajectory dominance may be ascertained by observing the azimuthal angular distribution of the detected hadron.) In the region of large virtual photon mass and missing mass (with their ratio fixed) the process may be picturesquely described as "deep-inelastic scattering of a lepton on a Reggeon target." We implement the assumed Regge behavior in the language of van Hove. The scaling behavior of the various structure functions is then determined by the "canonical" light-cone commutator (taken between spin-$J$ states), if certain smoothness assumptions are granted. Relations of the Callan-Gross type are also derived. The experimental features corresponding to our results are relatively easy to observe. The kinematics of coincidence electroproduction (with a polarized beam) is discussed in some detail.