n−pTriple Scattering ParameterRtat 203 MeV

The neutron-proton interaction has been studied by bombarding deuterons with 203-MeV polarized protons and observing high-energy neutrons recoiling into forward angles. The triple-scattering parameter $R_t$ was measured at neutron laboratory angles between 0° and 20°, using a spin-analyzing scatterer of liquid hydrogen, and detecting charge-exchange scattered protons therefrom. The measurements are related to the free $n-p$ scattering amplitudes by means of an impulse-approximation calculation which includes the $s$-wave final-state interaction between the incident proton and the proton in the deuteron. The measured values of $R_t$ are compared with the phase-shift solutions YLAN of Breit and collaborators, and the energy-independent solution of Arndt and MacGregor. Solutions YLAN 0, 1, 2, $2M$, and 3 do not agree with the date. Solutions YLAN 3M and 4M and the Arndt-MacGregor solution fit the data quite well.