High-twist production of prompt single photons at large transverse momentum

Quantitative predictions are presented for a specific hard-scattering reaction πN→γX in which both the incident meson and the produced prompt photon couple directly in the QCD amplitude. The process leads to a highly constrained class of events at large pT in which the photon momentum is balanced by that of a recoil quark jet, with no spectator jet of final-state particles emerging along the beam axis. Normalized absolutely in terms of the electromagnetic form factor of the pion, F_π(Q²), the cross section provides a lower bound on the total pT^-6 high-twist contribution to the inclusive prompt photon yield.