Schematic model for narrow Delta(1232) resonances bound in a nucleus - art. no. 064605

A schematic model explaining the recent evidence for bound states of the De lta (1232) resonance in C-12 With a width of about 5 MeV found in the C-12( e,e' p pi (-))C-11(g.s.) is suggested. It interprets the observed narrow re sonances as coherent bound states enforcing a fixed phase relation for the rescattering of the decay pi 's in the nucleus. The coherent summing of the rescattering diagrams results in a cancellation of the tails of the resona nce and a constructive interference in the maximum of the resonance leading to the observed narrow states at the maximum of the Delta (1232) shifted b y the binding energy. The same mechanism may contribute to narrow Sigma hyp ernuclear states and explains their successful and failed observation, resp ectively.