Analyzing Power of 3He(n, n)3He Between 1.60 and 5.54 MeV

We report the measurements of the analyzing power Ay(θ) of n-³He elastic scattering with unprecedented accuracy and angular coverage at five incident neutron energies between 1.60 and 5.54 MeV. To this end, we employed the polarization-transfer reactions ³H(p, n)³He and ²H(d, n)³He at 0° for neutron generation and a recently developed high-pressure ³He gas scintillator as an active target, enabling neutron-time-of-flight and ³He recoil-energy determinations. We obtained simultaneously the neutron polarization with a ⁴He-based polarimeter, capitalizing on the well-known n-⁴He Ay(θ). Our n-³He Ay(θ) data are compared to rigorous four-nucleon calculations using high-precision nucleon-nucleon potential models. The agreement between data and calculations is fair at the lower energies and becomes less satisfactory with increasing neutron energy. However, in comparison to the pure isotriplet p-³He system in the same energy region, the agreement between measured and calculated Ay is much better for the mixed (isotriplet and isosinglet) n-³He system, indicating large and somewhat counterintuitive isospin effects. We note that the incorporation of a Δ-mediated three-nucleon force in calculations of n-³He scattering was found to affect A y(θ) negligibly, suggesting the need for the reconsideration of fundamental interactions in resolving the four-nucleon analyzing power puzzle first established about a decade ago in p-³He scattering. © 2013 Springer-Verlag Wien.

Duke Scholars

Author Werner Tornow Physics