Cross-sections for the photoproduction of positive pions in hydrogen have been measured at the 1.1 GeV Frascati electron synchrotron for photon energiesE γ between 500 and 800 MeV and for π+ c.m. angles of θ=30o, 90o. The cross-sections exhibit a smooth behavior as a function of energy forE γ=(500÷600) MeV. No immediate evidence is found of a contribution of theP 11 resonance.
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Pions from the reaction γ + p → π + + n were analysed in the backward direction by a magnetic spectrometer. The photon energy region of 0.394 GeV to 1.397 GeV was covered by 19 different momentum settings. Data reduction resulted in 74 measured differential cross sections with statistical uncertainties typically from 4% to 8%. The systematic uncertainty was estimated to be ±5%. The data are compared to other recent experiments and predictions of phenomenological analyses.
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