The rates for forward electroproduction of single charged pions from deutrium have been measured in the resonance region, at a virtual photon mass squared ≈−0.5( GeV/ c 2 ) 2 . Results are presented in the form of a π − to π + cross-section ratio.
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Employing a neutral kaon beam at the Argonne Zero Gradient Synchrotron, a high-resolution magnetic spectrometer, and a neutron detector, differential cross sections have been obtained in the forward direction [0.045<|t|<0.18 (GeV/c)2] for the reaction KL0p→K+n. Previous studies of the time-reversed process in deuterium, K+d→K0p(p), have not yielded direct cross-section measurements in the forward direction because there is an inhibition of the non-spin-flip process in deuterium due to the Pauli exclusion principle. Nevertheless, our data are in agreement with the extracted free-neutron cross sections of deuterium studies as determined from the impulse and closure approximations.
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The reaction e − + p → e − + p + π 0 has been studied in the region of the Δ (1236) resonance at a four-momentum transfer of the virtual photon of 0.3 (GeV/ c ) 2 . Angles and momenta of the secondary electron and of the outgoing proton were measured in coincidence to obtain the angular dependence of the differential cross section. The angular distribution for s- and p-waves of the pion in the πN cm-system was fitted to the cross section for three W -bins around the maximum of the resonance. The contribution of the resonant multipoles M 1+ , E 1+ and S 1+ to the cross section as well as the contribution of the background amplitudes M 1− , E 0+ and S 0+ are given.
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The reaction e − + p → e − + p + η has been studied in the region of the S 11 (1535)-resonance by detecting the recoil proton in coincidence with the scattered electron. The reaction has been observed at three four-momentum transfers of the virtual photon: q 2 = 0.2, 0.28 and 0.4 (GeV/ c ). First results of the differential cross section measurements are given and compared with quark model calculations.
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The reaction γ+p→π0+p has been studied in three adjacent 100-Mev energy intervals between 900 and 1200 Mev and at pion center-of-mass angles of 47°, 90°, and 125°. The reaction was observed as a coincidence between the recoil proton and one of the photons from the meson's decay. The kinematics were determined by the energy of the incident photon and the angle of the recoil proton. The differential cross sections at the forward and backward angles show pronounced maxima near 1050 Mev, while the 90° cross sections decrease slowly with energy. The estimated total cross sections suggest a narrow maximum near 1050 Mev. These features are consistent with the previously proposed existence of a resonant state in the pion-nucleon system of total angular momentum 52.
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This paper reports measurements of the total cross section from 150 to 240 Mev of incident photon energy and measurements of the 135° differential cross section from 180 to 215 Mev. A Monte Carlo evaluation of the γ-ray telescope efficiency by means of an electronic digital computer is outlined. The combined results indicate that a small but finite amount of S-state production occurs and that the angular distribution becomes flatter as the energy decreases. The latter effect is associated with production in unenhanced P-states and with a lack of electric quadrupole production. Good agreement with the Chew-Low theory is demonstrated by a comparison between the photoproduction and scattering of π0-mesons, where the scattering cross sections are derived from those for charged mesons by charge independence.
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