Weak nonleptonic hyperon decays and hadronic loops.

Abstract

The influence of hadronic-loop effects on the SU(3) structure of the soft-pion contribution to the {ital S}-wave weak nonleptonic hyperon decays is studied in the framework of the unitarized quark model. The effects considered originate from the interference of strong and weak amplitudes of the {ital P}-wave hyperon decays. When the baryon-pole model is used to describe the latter it is found that the quark sea generated by hadronic loops renormalizes the sizes of the two independent SU(3) amplitudes from their naive quark model ratio of {ital f}/{ital d}={minus}1 to {ital f}/{ital d}{approx}{minus}1.6. This is in remarkably good agreement with the phenomenological estimate of the soft-pion contribution performed by Pham who, after subtracting the terms violating the modified Lee-Sugawara relation, obtained ({ital f}/{ital d}){sub soft} pion={minus}1.5. A brief discussion of the uncertainties resulting from our poor knowledge of the meson-pole contribution is also included.