Über die Berechnung der Photoerzeugung von π0 aus Streudaten
The cross section forπ0-production is calculated from the results of the dispersion relation approach ofChew, Goldberger, Low andNambu and compared with the experimental data. The predictions are made using the measured values of all scattering phase shifts. A fit of the theoretical result toσ(90‡) between 260 and 370 MeV givesf2=0,082. There is no systematic deviation from the predictions forσ (90‡) up toEγ=450 MeV. The general behavior of the asymmetry coefficientB is correct. A quantitative comparison which would show the contribution of the unknown electric dipole termN(+) ofChew et al. is only reasonable after the calculation ofB and the measurements have been improved.C/A depends strongly on the small phases up to 240 MeV. The effects of the small phases are pretty large forσ(l50‡) but there is no discrepancy similar to the results forπ+-production above 290 MeV.The formula for the cross section does not reduce to the results of the phenomenological theories ofBrueckner-Watson, Sachs et al. andFeld, if the simplifications made by these authors are taken into account. The origin of the differences is discussed.