NEUTRON-DEUTERON ELASTIC SCATTERING ABOVE THE BREAKUP THRESHOLD

Abstract

This chapter discusses the three-nucleon scattering problem, with local two-nucleon potentials, using the method of complex coordinates to calculate scattering amplitudes. The method is similar in practice to use of a Kohn variational principle but avoids the need for including complicated asymptotic terms representing three free particles, the latter being required by a Kohn principle in the energy region above the deuteron-breakup threshold. The method provides an alternative to those that first calculate the two-nucleon t-matrix, often in a separable approximation, and then apply techniques based on the Faddeev equations. The basic equation of the complex coordinate method for elastic n–d scattering is a variational expression for the elastic amplitude. The chapter explains that quartet amplitudes are relatively insensitive to the form of the nucleon–nucleon interaction. Singlet repulsion is a necessary feature in three-body calculations. The two-nucleon potentials of local and separable types, although indistinguishable in reproducing two-nucleon scattering data, give different three-nucleon results.