SINGLE-PI+- AND -K+ PHOTOPRODUCTION FROM COMPLEX NUCLEI AT 8-GEV AND 16-GEV

The reactions γA→π±A* have been studied at four-momentum transfers -t<~0.5 GeV2 for seven elements ranging from hydrogen to lead. Exclusion-principle suppression is clearly visible at small-momentum transfer. Neither the A dependence nor the energy dependence of the cross sections agrees with the predictions of the vector-dominance model. The ratio of π-π+ production requires equal spatial distributions for the protons and neutrons in nuclei. Some K+ data are also presented. © 1969 The American Physical Society.