Measurement of Neutron-Proton Polarization at 126 MeV

The $n-p$ polarization at 126 MeV has been measured between 33 and 82° c.m. by scattering a 41% polarized neutron beam from liquid hydrogen. The energy threshold and angle of scattering were determined by a range-threshold neutron counter. By the use of a conjugate counter to detect the recoil protons in coincidence with the scattered neutrons, the background rate was held to about 10%. Many systematic errors were eliminated by the use of precession magnets to reverse the sign of the neutron polarization. The maximum polarization was found to be 0.580±0.040 at 56° c.m. This maximum is higher than that obtained in any of the Yale phase-shift predictions.