Measurement Of The Gamma P -> Pi(+)N Reaction Near Threshold

Differential cross sections for the gamma p --> pi(+)n reaction have been measured at photon energies 1 to 2 MeV above threshold using tagged-photon beams. The electric dipole amplitude E0+ deduced at threshold is compared to recent predictions from chiral perturbation theory. Constraints on the value of the pi N coupling constant are inferred by combining theory and experiment.