Neutron experiments at LAMPF

The problem of the nucleon-nucleon force is the most fundamental in nuclear physics and is basic to particle physics. However, in the energy range from pion production threshold to 1 GeV, the N-N interaction is rather poorly determined. In general, at these energies, there is no unique set of phase shifts and coupling parameters; the I = 1 parameters are known at least quantitatively, but the I = 0 parameters are not even known qualitatively. This is illustrated by the variation of 3S1 phase shift from -17 to 350 in the three solutions of the energy-independent nucleon-nucleon phase shift analysis of Glonti. In addition, these results are in considerable disagreement with the analyses of MacGregor. This is due to the paucity of the n-p scattering data including polarization and triple scattering parameters. Furthermore, as will be shown later, there is considerable disagreement between the results from different groups in the intermediate energy region of even so basic an observable as the n-p differential cross section. Therefore, a long range program was started for the definitive determination of the n-p interaction at LAMPF energies (300 to 800 MeV). This is an ambitious project which will ultimately require the performance of many experiments. Each successive set of measurements will clarify our understainding of the n-p system to some degree and simplify the problems of the subsequent measurements. In this communication a general description of the experimental setup and the various neutron experiments performed at LAMPF is given