High-Energy Photoproduction of Charged Pions at Backward Angles

Measurements on large-angle photoproduction of π⁺ mesons from hydrogen have been made at the Stanford Linear Accelerator Center for photon energies between 5 and 15.5 GeV and u values from +0.05 to -1.8 (GeV/c)². The measured cross section decreased with energy approximately as k^-3, showing no shrinkage in this range of u values. Furthermore, it had a smooth u dependence with no sign of a dip at u-0.15 (GeV/c)² as would be expected from nucleon exchange. π^-Δ⁺⁺ production was measured at 5 GeV and shows a rapid decrease with increasing $|u|$.