Evidence for SU(3) breaking in Cabibbo-type fits of semileptonic hyperon decay

Abstract

We analyze recent precision experiments involving semileptonic hyperon decay and demonstrate that there exists definite evidence for SU(3) breaking. The type of breaking observed is a difference in the $\frac{D}{\mathrm{}(F+D)\mathrm{}}$ ratios in the $\Delta S=0\mathrm{}$ and $\Delta S=1\mathrm{}$ sectors, which is at variance with the simplest quark-model expectations. We comment on the relevance of symmetry breaking to the determination of weak mixing angles.