Status of Experimental Photonuclear Results

The absolute majority of data on photoneutron reaction cross sections have been obtained in experiments with bremsstrahlung radiation and quasi-monoenergetic photons produced during the in-flight annihilation of relativistic positrons. There are significant disagreements between the results of these two types of experiments in both the absolute value and shape of the cross sections in the energy range of the giant dipole resonance (GDR). For instance, in cross sections obtained using bremsstrahlung -radiation beams, distinct structural features are observed, which are practically absent in the corresponding cross sections obtained with annihilation photon beams. The disagreements in absolute value are obviously systematic: they directly depend on method of data obtaining and significantly exceed the statistical uncertainties achieved in the experiments. Significant disagreements are also observed between the results of experiments of the same type. In joint systematic studies of a large amount of data on cross sections of various photonuclear (primarily photoneutron) reactions, both total and partial, obtained in different experiments, possible reasons for the disagreements in photonuclear experiment results have been identified, their status, methods for accounting, and eliminating the observed disagreements are discussed.