Zero-crossing Angle of the N-P Analyzing Power.

The angles at which the n-p elastic scattering neutron analyzing power A(00n0) crosses zero were measured with precision at four TRIUMF energies below 300 MeV. The mean interaction energies are also measured with greater precision than in previous experiments. The results are E(n)=175.26+/-0.23 MeV, theta=98.48 degrees+/-0.28 degrees; E(n)=203.15+/-0.20 MeV, theta(zx)=91.31 degrees+/-0.18 degrees; E(n)=217.24+/-0.19 MeV, theta(zx)=87.64 degrees+/-0.18 degrees; and E(n)=261.00+/-0.16 MeV, theta(zx)=80.18 degrees+/-0.19 degrees. After correction for charge symmetry breaking effects, the energy where the averaged neutron-proton analyzing power crosses zero at theta(zx)=90 degrees is found to be E(n)=206.8+/-0.6 MeV.