The scattering amplitude for NN → NΔ is decomposed into sixteen independent spin-space operators Oi, where the corresponding coefficients Ai only depend on scattering angle, incoming energy, and the Δ -mass. In addition to the commonly used vector spin-transition matrix, it is necessary to also employ a tensor spin-transition matrix. The Oi can be chosen in two ways, either to facilitate discussion of underlying dynamical mechanisms or to simplify the antisymmetrization with respect to the initial nucleons. Relations between the Ai(θ) and the (LSJ) partial-wave amplitudes are given. We evaluate the Ai using partial-wave amplitudes calculated elsewhere in a unitary three-body model with one-pion-exchange driving terms. Many amplitudes are of competing importance after antisymmetrization, and they are strongly dependent upon incident energy and Δ invariant mass.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics