Measurement of then−pSpin-Correlation ParameterAyyat 50 MeV

The neutron-proton spin-correlation parameter, $A_{\mathrm{yy}}$, has been measured at four angles using a 50-MeV polarized neutron beam and polarized proton target. The measured values have been included in new phase-shift analyses of the 50-63-MeV data, producing for the first time (at these energies) a definite and positive value 2.6°±1.0° for ${\overline{\epsilon }}_1$, the important $3S_1-3\mathrm{}{D}_1$ phase-shift mixing parameter of the $n-p$ system.