Medium-energy theory group. Progress report, July 1, 1976--June 30, 1977

Research carried out during the contract period by R. A. Bryan, principal investigator, and associates R. B. Clark and B. J. VerWest is reported. Most of the work has centered on the nucleon-nucleon interaction at low to intermediate energies and has ranged from purely theoretical studies, such as the behavior of two-pion-exchange Feynman amplitudes at far off-shell initial and final nucleon momenta, to the more practical work of phase-shift analyzing nucleon-nucleon data. One has also investigated the possibility that the NN interaction is not invariant under time-reversal and have provided predictions for some relevant experimental observables for the case where such time-irreversibility is due to short-range processes. Finally, research on topics which fall in the domain of elementary-particle physics but which are felt can lend guidance in trying to determine the NN force at very short distances is completed; this is the current frontier in nucleon-nucleon research. A list of publications is included