Analyzing-Power Measurements for the 2 H(n, pn)n Reaction at 187 MeV

Abstract

Analyzing-power measurements were performed for the 2 H(n, n)2 H and 2 H(n, pn)n reactions at 189 MeV at the Indiana University Cyclotron Facility. A polarized neutron beam was obtained using polarized protons incident upon a liquid deuterium target. Neutrons emitted at 10° were collimated into a beam 5 cm wide by 7 cm high, with a polarization of ~ 0.55 and an intensity of ~107/s. The neutron beam was incident upon a second liquid deuterium target to study the reactions of interest. Charged particles were detected in an array of plastic scintillator and wire chambers and neutrons were detected in an array of six segmented, mean-timed plastic scintillators, each 10 cm by 10 cm by 1 m, at a flight path of 2 m. The overall energy resolutions were about 10 to 15 MeV. The analyzing powers from the 2 H(n, n)2 H reaction agree well with measurements from 2 H(p, p)2 H at nearby energies, indicating no significant Coulomb effects in the latter at these energies. The 2 H(n, pn)n reaction was studied in two geometries; a quasifree scattering (QFS) geometry and a final-state interaction (FSI) geometry. The QFS geometry is not expected to be sensitive to 3-body forces while the FSI geometry is predicted to have a strong sensitivity to such forces. We find that the analyzing powers from the QFS geometry generally agree with those from free 1 H(n, n)1 H scattering as expected and that the analyzing powers from the FSI geometry may indicate the presence of 3-body forces in the nuclear interaction.