In this paper we review the present status of the πNNN-NNN problem. In particular, we reconsider the chain-labeled approach recently proposed by us, and identify a class of graphs, previously overlooked, which prevents the kernel of the corresponding πNNN-NNN equations from being connected. We propose some approximate schemes, yielding connected-kernel equations. A generalization of the residue method allows us to relate the transition amplitudes for the coupled πNNN-NNN system to the chain-labeled formalism. The quasiparticle approach is extended to the present situation, where emission/absorption of particles is allowed. The open problems for the πNNN-NNN system in light of the present and of previous approaches are finally discussed.

The pion--NNN--NNN problem: Connectedness, transition amplitudes, and quasiparticle approximation

CATTAPAN, GIORGIO;
1997

Abstract

In this paper we review the present status of the πNNN-NNN problem. In particular, we reconsider the chain-labeled approach recently proposed by us, and identify a class of graphs, previously overlooked, which prevents the kernel of the corresponding πNNN-NNN equations from being connected. We propose some approximate schemes, yielding connected-kernel equations. A generalization of the residue method allows us to relate the transition amplitudes for the coupled πNNN-NNN system to the chain-labeled formalism. The quasiparticle approach is extended to the present situation, where emission/absorption of particles is allowed. The open problems for the πNNN-NNN system in light of the present and of previous approaches are finally discussed.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/116403
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