165We thank Professor L. Alvarez for making the bubble chamber available. Professor E. Segre provided valuable support and encouragement continuously and we express our gratitude to him. W. Gage, B. Douglass, and Miss M. Corey contributed invaluably to the programming efforts and the scanning and measuring personnel contributed with their usual skill and industry.The polarization of the proton produced by the photodisintegration of the deuteron has been measured at several angles for photon energies between 170 and 450 MeV. The polarization is found to be around -0.20 (Basel convention) for 90° cm. and photon energies between 200 and 300 MeV. This is in reasonable agreement with a calculation by D. George based upon the Austern model. However, the calculation fails to explain the strong increase in polarization with increasing photon energies. At a photon energy of 450 MeV and 90° cm. the proton polarization is as large as -0.60.
to be published. For an exposition of the Hartree-FockWe have measured the photoproduction of the rf meson in the region from threshold to -940 MeV. The differential cross section near 90° in the center of mass is characterized by a rapid rise near threshold reaching a maximum value of -1 lib/sr approximately 40 MeV above threshold. The cross section then decreases to a value of 0.3 jub/sr at a laboratory photon energy of -900 MeV. Several different angles have been measured at a laboratory photon energy of 790 MeV and the angular distribution is consistent with isotropy. This implies either an S or P wave with T = - §, J = | near threshold. Recent phase-shift analyses of pion-nucleon scattering suggest that the rf production near threshold is to be identified with the iV 1/2 *(1550 MeV) S u state.Photoproduction cross-section measurements of the eta, a pseudoscalar meson with positive G parity and mass 548.6±0.4 MeV, have previously been obtained at higher photon energies than the range covered by this experiment. 1 More recently, the Frascati group has extended its measurements to lower energies and there is thus some overlap between the present experiment and the Frascati results. 2 In addition, there are new data in the region from 950-1100 MeV from Heusch et al. 3 However, all these previous experiments measure the rf production for decay into a specific channel, viz., rf -+Y + y. Comparison with the present results thus requires a knowledge of ^yy/^total' the branching ratio for the two-photon decay mode as compared with all other channels.Observation of rf photoproduction in the re-method see M.
The polarization of recoiling protons from the photoproduction of 7r° mesons on liquid hydrogen has been measured for primary photon energies between 500 and 1000 MeV over a range of 7r° cm. angles from 55° to 130°. The results show structure not observed previously in experiments of less precision. In particular, the polarization at 90° cm. is close to zero at a primary photon energy of 900 MeV. Also, a strong dependence of polarization on x° cm. angle between 600 and 900 MeV was observed. A subsidiary measurement of the polarization of the recoil protons from elastic e-p scattering at 900 MeV and q 2 = 10 F~~2 gave a value (1.3db2.0)%.
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