Ondes partielles et modèles d'échange dans les réactions πN → ππN

Abstract

We present a theoretical framework to be used in the analysis of the experimental data for the reaction πN → ππN in terms of partial wave amplitudes and amplitudes corresponding to peripheral production of N* and ρ. In this paper, we express the amplitudes in terms of Pauli spinors and matrices while a second paper will derive the results in terms of spherical harmonics and Clebsch-Gordan coefficients. Our final amplitude contains adjustable parameters corresponding to various admixtures of the partial wave and exchange amplitudes. We point out the presence of Minami-type ambiguities in πN → ππN partial wave analysis and finally we develop the partial wave expansion of exchange amplitudes.