6533b7d1fe1ef96bd125d622

RESEARCH PRODUCT

Formal theory for two-particle channels

subject

description

The general formalism has been developed over many years by various authors. One starting point is the work of de Swart (DSw 59) who has considered electric multipoles in the long-wave-length limit using the Siegert theorem and as magnetic contribution only the dipole spin-flip transition. The T-matrix is then expanded in terms of reduced multipole amplitudes. This approach has been generalized by Donnachie (Don 62a) and Partovi (Par 64) by including higher electric and magnetic multipoles. Furthermore, the electric multipoles are not restricted to the long-wave-length limit and the additional terms besides the Siegert operators (see section 4.1) are included. Using techniques from angular momentum algebra Cambi, Mosconi and Ricci (CaM 82a) have considerably simplified the expressions for differential cross section, photon asymmetry and nucleon polarization expressing them in terms of Legendre polynomials or functions, respectively. That has subsequently been generalized to all polarization observables in Are 88a.