Four-quark operators in hyperon radiative decays and Hara's theorem

Abstract

We demonstrate that in the effective Hamiltonian for the process $s+u\ensuremath{\rightarrow}u+d+\ensuremath{\gamma}$, one can identify two types of local four-quark operators; type I operators violate Hara's theorem and type II respect it. By an explicit calculation we demonstrate that the quark-quark bremsstrahlung process generates both types of operators but only type I survive in the SU(3) limit.