Photoproduction of Pion Pairs in Hydrogen

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The multiple photoproduction of pions has been observed by detecting, in a magnetic spectrometer, the negative pions which emerged at 60[degrees] and at 120[degrees] from a high-density hydrogen gas target in the bremsstrahlung beam of the electron synchrotron at the California Institute of Technology. The yields of negative pions "per equivalent quantum" were measured for several values of pion energy and bremsstrahlung cut-off energy. From the variations of the yields with bremsstrahlung cut-cuff energy, the cross-section for multiple production of pions was obtained. The cross-section shows no large dependence on the angle of emission of the pion from 90[degrees] to 150[degrees] in the C.M. system. The integral of the cross-section over pion energy is consistent with a constant value [...] = 4 x 10[...] cm[...]/ster. for all photon energies between 600 and 1100 Mev. No theoretical prediction is yet available at the photon energies considered in this experiment. The observed dependence of the cross-section on pion energy has been compared to some phenomenological models