Applications of chiral perturbation theory: Mass formulas and the decay 3

Several new results on the breaking of chiral SU(3) × SU(3) are presented within the theoretical framework of chiral perturbation theory. (a) The leading-order corrections to the Gell-Mann-Okubo formula for the baryon octet are shown to be of order 32, where is a chiral symmetry breaking parameter. An explicit exact expression is given for the leading-order corrections, which provides a new development in understanding why this formula works so well. Similarly the corrections to the Gell-Mann-Okubo formula for the ground-state pseudoscalar octet are shown to be of order 2ln (including - mixing). On the basis of these exact results it is argued that SU(3) × SU(3) symmetry is as good as SU(3) symmetry 30% except when one considers electromagnetic interactions. (b) We examine the 3 decay on the assumption that it is regulated by a nonelectromagnetic isospinviolating term of the type 3u3 with u3 a member of 3333. The strength 3 of this term is related to the experimental rate including all leading-order chiral-symmetry corrections. This estimate of 3 leads to I=1 hadron level shifts about a factor of 2 or 3 too large, although our estimate of 3 depends sensitively on the experimental details. (c) Octet enhancement, an exact formalism to describe - mixing, and other topics are discussed.