Scattering of 262-keV Polarized Neutrons byHe4

Abstract

The analyzing power of ${\mathrm{He}}^4$ for 262-keV polarized neutrons has been measured at a scattering angle of 89° c.m. Neutrons of known polarization were obtained from a radioactive ${\mathrm{Na}}^{24}$-D photoneutron source. The left-right asymmetry in the scattering from a liquid helium target was observed. Neutron spins were inverted by precession in a solenoid. The result, $P=+0.21\mathrm{}\pm 0.06$, is slightly higher than, but consistent with, new phase shifts calculated by Roper from available $n-{\mathrm{He}}^4$ data.