Possibility of Non-Octet Axial-Vector Currents

Three models of axial-vector currents which contain both octet and non-octet components are examined. The first model is based upon the $\Delta U=\frac{1}{2}$ rule, and it forbids decays with $\Delta S=-\Delta Q$ and $\Delta S=2\mathrm{}$. The second model conserves a "weak hypercharge," and introduces $\Delta S=-\Delta Q$ and $\Delta S=2\mathrm{}$ terms in a specific way. The third model assumes that the usual $\Delta T=1\mathrm{}$ and $\Delta T=\frac{1}{2}$ 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.