Gluon-Exchange Contributions to Nonleptonic Hyperon Decays

Abstract

Recently, it has been demonstrated by Itoh et al. 1) that the inequality of relative distances between quarks in a baryon plays a significant role in the electromagnetic mass differences (EMMD) of 1/2+ baryons and 0mesons. It has been argued that the effect of the spin-spin interactions in altering the relative spatial distribution of quarks in a baryon must be considered in a dynamical quark model. This produces a nice fit for the experimentally observed EMMD's and results in a negative value for neutron's charge-radius. In this paper, we extend the above considerations (i.e., consider a spatially dependent spin-spin interactions) to the nonleptonic hyperon decays and calculate one gluon-exchange effects. Since the spin-spin force is repulsive between quarks with parallel spins and attractive between quarks with anti-parallel spins, the quark pairs in a spin-1 state will be, on the average, farther apart than those in spin-O state. We assume that baryon-wavefunctions are gaussian and depend upon the different interquark distances. The basic interaction between quarks is taken to be of Fermi-Breit type.!),2) It is known 3 ) that in the current-current picture of weak Hamiltonian with (V ~ A) charged currents, the quark-quark scattering