Energy dependence of analyzing power Ay and cross section for p+d scattering below 18 MeV.

The vector analyzing power ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}) of the $^{2}\mathrm{H}$(p\ensuremath{\rightarrow},p${)}^{2}$H scattering has been measured at ${\mathit{E}}_{\mathit{p}}$=5, 6, 6.5, 7, 8, 8.5, 9, 10, 12, 14, 16, and 18 MeV with a typical statistical accuracy of 0.0009 and an uncertainty in the beam polarization of less than 0.7%. The differential cross section \ensuremath{\sigma}(\ensuremath{\theta}) of the $^{2}\mathrm{H}$(p,p${)}^{2}$H scattering has also been measured with a typical uncertainty of 0.8% using unpolarized beams of the same energies and of 2, 2.5, 3, and 4 MeV. A large discrepancy of about 25% between the experiment and the Faddeev calculation with the Paris NN potential is observed at the maximum of ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}) around ${\mathrm{\ensuremath{\theta}}}_{\mathrm{c}.\mathrm{m}.}$=120\ifmmode^\circ\else\textdegree\fi{}. This discrepancy is shown to be reduced by modifying LS force in the NN potential, though a discrepancy still remains in the energy dependence of the ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}) maximum. At the minimum of \ensuremath{\sigma}(\ensuremath{\theta}) around ${\mathrm{\ensuremath{\theta}}}_{\mathrm{c}.\mathrm{m}.}$=120\ifmmode^\circ\else\textdegree\fi{}, a large discrepancy ranging from -19% at 2 MeV to +24% at 18 MeV is observed between the experiment and the calculations with either of the original and the LS-modified NN potentials. This indicates that an improvement is also necessary in the scalar part of the potential. The difference in the ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}) maximum between the p\ensuremath{\rightarrow}+d and the n\ensuremath{\rightarrow}+d scatterings is discussed.