Photoproduction of Positive Pions from Hydrogen in the 600 to 1000 Mev Region

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. A magnetic spectrometer and scintillation counter system was used to detect pions from the reaction [...] + P ---->[...] + N initiated in a liquid hydrogen target by the bremsstrahlung beam of the Caltech Synchrotron. Observations were made at five mean laboratory photon energies, k = 600, 700, 800, 900, and 1000 Mev. At each energy measurements were made in the angular range [...] to [...] in the center-of-momentum system to provide differential cross sections at eleven angles. The results are presented in the form of angular distributions in the c. m. system for each value of k. These differential cross sections have been integrated to provide total cross sections, whose variation with energy gives a peak at 700 Mevo. Also, the 1000 Mev value is slightly above the 900 Mev total cross section and the 1000 Mev angular distribution indicates the strong influence of a higher angular momentum state thought to be J = 5/2. The peak at 700 Mev and the behavior at 1000 Mev are interpreted to be effects of two resonances in the pion-nucleon system. The "second resonance" near 700 Mev is consistent with an isotopic spin and angular momentum I = 1/2 and J = 3/2, respectively, and the "third resonance" is presumed due to an I = 1/2 and J = 5/2 state. Arguments to support an assignment of [...] for the second resonance and [...] or [...] for the third resonance at 1050 to 1100 Mev are offered