PHOTON-INDUCED EMISSION OF PIONS AND PROTONS FROM VARIOUS NUCLEI IN THE DELTA-RESONANCE REGION

Double differential cross sections for the photon induced emission of pi-, pi+ and protons from Be, C, O, Ti, and Pb have been measured in the photon energy range k = 220-450 MeV using the tagged photon beam of the Bonn 500 MeV synchrotron. The hadron detector consists of a magnetic spectrometer and a large acceptance scintillation counter array. For Be, the single-arm energy distributions show clear structures from quasi-free pion production and quasi-deuteron photodisintegration. These structures disappear with increasing target size. The dependence of the differential cross section on the nuclear size S at THETA-lab = 52-degrees can be described by the power law d-sigma/d-OMEGA proportional-to S-alpha, where S is the number of protons or neutrons, respectively. The exponent is alpha-pi almost-equal-to 0.6 for pi- and pi+ and alpha-p almost-equal-to 1.15 for protons. Data for pn, pp, and p-pi coincidences are presented. The results are compared to intranuclear cascade codes (PICA and PIKI) and to microscopic calculations.