We have measured the shape of thep+p cross section at five energies from 6-10 MeV (lab) using solid targets. Our results resolve discrepancies in values of the shape-sensitive central p-wave parameter \ obtained from the gas-target data of other groups. We agree particulary well with data which had suggested difficulties in reconciling both high-and low-energy data with one-boson-exchange models of the nucleon-nucleon interaction.The study of thep + p interaction to elucidate the fundamental properties of the nucleon-nucleon force has had a long history. This force proves to be exceedingly complex, and it is necessary to obtain precise experimental measurements of nucleon-nucleon scattering over a wide range of energy in order to determine its general phenomenology. Although considerable progress has been made in developing a field theory for the interaction, this goal is far from having been achieved, and it is likely that detailed experimental information will provide an essential guide to theorists for some time to come.It was in this context that we studied the situation at energies near 10 MeV, where there remain disturbing discrepancies in the experimental data. Discussions of the status of our understanding of the£ + p interaction in this low-energy region include the work of Sher, Signell, and Sher, 1 Holdeman, Signell, and Sher, 2 Jarmie et al., 3 Slobodrian, 4 Imai et al., 5 and Naisse. 6 The reported 1 ' 2 * 5 disagreements in angular shape of the experimental p+p differential cross sections are of particular interest for the present work and appear as discrepancies in the extracted central/)-wave parameter A c . An example is a recent 5 comparison of A c values extracted from four different data sets 3 ' 5 ' 7 ' 8 in the 5-10-MeV energy range, which showed little agreement among the sets. We feel that such a situation is intolerable for an interaction of such fundamental importance to nuclear physics. Furthermore, the energy region near 10 MeV is particularly important because, 5 according to field-theoretic ideas, A c in this energy range is sensitive to the competition between the repulsive (£-wave) force due to one-pion exchange, and the attractive force due to correlated (scalar, isoscalar meson) or uncorrelated two-pion exchange.The emphasis in the present work was to mea-sure accurate angular shapes of thep +p differential cross section. This was accomplished by using solid targets (polystyrene, which contains C and H), good detector geometry, and monitor detectors. The main purpose was to perform an experiment of high accuracy which would not have sources of angle-dependent errors identical to those of the other (gas-target) experiments in this energy region. Our method did not yield an accurate absolute normalization; however, we chose to take measurements at lab energies (known to about 5 keV) of 5. 957, 6.968, 8.030, 9.690, and 9.918 MeV at which gas-target data exist, 3f5 ' 7 ' 9 and for the purpose of performing phase-shift analyses, we normalized our results by using the gas-target data ...
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