This award supports Dr. R. S. Hicks and others of the Medium Energy Nuclear Physics Group of the University of Massachusetts to collaborate with physicists from Sweden, the Netherlands and the United Kingdom in an experiment to be carried out using the continuous photon beam produced by the University of Lund accelerator facility. Comparable beams of known-energy photons are currently not available in the United States. The main European collaborators are Dr. G. van der Steenhoven, principal spokesperson of a Dutch group primarily from the National Institute for Nuclear and High Energy Physics, D. Branford and D.G. Ireland of Edinburgh University, and B. Schroeder of the Photonuclear Reactions Group, University of Lund. The primary objective of this nuclear physics experiment is to improve the understanding of mechanisms by which nucleons are ejected from the nucleus as a result of an electromagnetic interaction with an incident electron or gamma ray. Specifically, the cooperating scientists will measure the momentum vectors of protons ejected from the nucleus as a result of the absorption by the nucleus of photons of known energy. This study should give fresh insights into reaction mechanisms for single-nucleon knockout in the kinematic region where meson exchange currents and short-range interactions are important. Such an understanding is required in order to correctly interpret certain reactions to obtain comprehensive and detailed information on the distributions of single nucleons inside nuclei.
