| Angular distributions of cross sections and complete sets of analyzing powers have been measured for d-p scattering at a center-of-mass energy of 667 +/- 1 keV. This set of high-precision data was compared to the most recent variational calculations with the nucleon- nucleon potential AV18 alone and with AV18 plus the UR three-nucleon potential. The calculations have the best agreement with the cross-section data while the comparison with the tensor analyzing powers showed good agreement. However, a comparison between the vector analyzing powers revealed differences of approximately 40% in the maxima of the angular distributions. These NAP discrepancies have been observed at Ec.m. ≥ 2.0 MeV as well as in the n-d scattering case. After the n-d experiments, the problem has been labelled the " Ay Puzzle". A chi2/datum analysis was performed with the lowest values achieved by the inclusion of a three-nucleon force in the theoretical calculations. This fact provides more credence for the existence of three-nucleon forces. However, the chi2/datum for the VAPs remained approximately 100. To investigate the root of the problem in addition to other differences between the theory and the data, a single-energy phase shift analysis (PSA) was performed. The best fits to the NAP data displayed an ≈20% increase in the mixing parameter e32- and an increase in the splitting between 4 PJ phase shifts from the variational calculations with the AV18+UR potentials. |
