Phenomenological Chiral Model for Nonleptonic Hyperon Decays

Abstract

The $S$- and $P$-wave nonleptonic hyperon decay amplitudes are calculated using a chiral-invariant effective Lagrangian. This reproduces the current-algebra results in a very simple way, the baryon pole diagram arising without any ambiguity whatsoever. As is well known, this leaves us with the wrong ratio of $S$- to $P$-wave amplitudes. It is noted that one way out of this dilemma is to add another term to the effective Lagrangian which vanishes in the limit of zero pion four-momentum, and hence contributes to the physical answer without contributing to the current-algebra result. The addition of the ${K}^{*}$ pole diagram leaves us with a rough three-parameter fit to all the amplitudes plus the $K\ensuremath{\rightarrow}2\ensuremath{\pi}$ amplitudes.