Possibility of Non-Octet Axial-Vector Currents

Abstract

Three models of axial-vector currents which contain both octet and non-octet components are examined. The first model is based upon the $\ensuremath{\Delta}U=\frac{1}{2}$ rule, and it forbids decays with $\ensuremath{\Delta}S=\ensuremath{-}\ensuremath{\Delta}Q$ and $\ensuremath{\Delta}S=2$. The second model conserves a "weak hypercharge," and introduces $\ensuremath{\Delta}S=\ensuremath{-}\ensuremath{\Delta}Q$ and $\ensuremath{\Delta}S=2$ terms in a specific way. The third model assumes that the usual $\ensuremath{\Delta}T=1$ and $\ensuremath{\Delta}T=\frac{1}{2}$ rules are valid even when the octet rule is not. Although present data on semileptonic hyperon decay are not accurate enough to determine the precise admixture of non-octet components, they seem to indicate that such currents are restricted to the 27 representation, and that they may form about 10% of the total current. Throughout the discussion the conserved-vector-current hypothesis is assumed to hold. Some of the general theoretical consequences that would follow from the existence of non-octet axial-vector currents are also considered.