LargeP T photoproduction in the hard scattering expansion

Largep _T photoproduction is studied in the hard scattering expansion, including both three- and four-jet processes. The higher twist corrections (∝p _T ^?6 andp _T ^?8 ) to the basic QCD hard scattering process (∝p _T ^?4 ) are estimated using the constituent interchange model and the various terms compared. Both single jet inclusive cross sections and single particle inclusive π⁰ cross sections are evaluated, the latter using scale violating fragmentation functions. We find that the higher twist terms are significant at present energies, particularly for three-jet events, though the four-jet anomalous photon contribution can be measured. Three-jet QCD processes require considerably higher energies to provide a significant contribution to the cross section. Methods of separating the different processes experimentally are discussed.