Spin Dependence in Low-Energy Neutron-Proton Scattering

The analyzing power in neutron-proton scattering at 25 MeV neutron energy has been measured to an accuracy of typically ± 0.002 for c.m. scattering angles between 50° and 165°. Contrary to the conclusions reached from earlier precision measurements at 16.9 MeV, the contributions to partial waves with $l\ge 3$ are consistent with predictions based on one-pion exchange. The new data are well described by the Paris potential and by a recent global phase-shift analysis.