Measurement of a mixed spin-spin correlation parameter fornpelastic scattering

The mixed spin-spin correlation parameter $C_{\sigma \sigma }\approx 0.5C_{\mathrm{SS}}-0.8\mathrm{}{C}_{\mathrm{SL}}$ for $\mathrm{np}$ elastic scattering was measured for incident-neutron-beam kinetic energies of 484, 634, and 788 MeV over the center-of-mass angular range 75°-180°. These $C_{\sigma \sigma }$ data are important for determining the $I=0\mathrm{}$ nucleon-nucleon amplitudes and provide strong constraints on the phase-shift solutions. It was found that the ${}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$, ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$, and ${}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ isospin-0 partial waves are most strongly affected.