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The momentum spectrum of the recoil protons in the reaction γ + p → p + anything is measured in the incident energy range from 710 MeV to 950 MeV. A tagged photon beam is used as an incident photon. From this measurement the cross sections of the reactions, γ + p → p + π+ + π− and γ + p → p + π0 + π0, are obtained as functions of the energy of the incident photon. The observed ratio of these two reactions ( p + π 0 + π 0 ) ( p + π + + π − ) is about 0.2 in the incident energy region investigated, and is consistent with the excitation of the isospin - 1 2 intermediate state in the s-channel. No serious deviations from the phase space are observed in the missing-mass spectrum of protons.

The differential cross sections for γp→π+n from hydrogen and the π − π + ratios from deuterium were measured at nine c.m. angles between 30° and 150° for laboratory photon energies between 260 and 800 MeV. A magnetic spectrometer with three layers of scintillation hodoscope was used to detect charged π mesons. The cross section for γn→π−p was obtained as a product of d σ d Ω (γ p →π + n ) and the π − π + ratio. The overall features in the cross sections of the two reactions, γp→π+n and γn→π−p, and in the ratios, π − π + , agree with predictions by Moorhouse, Oberlack and Rosenfeld, and Metcalf and Walker. An investigation of the possible existence of an isotensor current was made and a negative result was found. In detailed balance comparison with the new results on the inverse reaction π−p→γn, no apparent violation of time-reversal invariance was observed.

The experiment is performed to measure the total pair production cross sections of photons for hydrogen in the energy range from 330 MeV to 910 MeV. The experimental cross sections obtained are in good agreement with the theoretical cross sections by Jost, Luttinger and Slotnick.

The differential cross sections for the reaction γ + n → π 0 + n have been measured at pions angles of 45°, 60°, 105°, 120° and 140° in the c.m.s. for photon energies of 500–900 MeV. Both π 0 meson and recoil neutron from a liquid deuterium target were detected with a pair of Cerenkov counters combined with lead spark chambers and a hodoscope consisting of 16 modules of plastic scintillation counters. The experimental results were compared with the recent phenomenological partial-wave analysis, and indicate that the ratio of the isoscalar part to the isovector part of the resonant amplitude of B 2 _(N′(1520)(D 13 )) is only about 0.2, and that in the γ + n → π 0 + n reaction there is no remarkable enhancement due to the N′(1470)(P 11 ) resonance.