Quark-diagram analysis of hyperon radiative decays. General formulation

We calculate hyperon radiative decays using quark-diagram analysis taking both weak and electromagnetic interactions to be short-distance processes. The second-quantized quark fields are expanded in terms of MIT bag modes, so as to be consistent with quark confinement. In this paper, we present the general formulation of the quark-diagram calculation and use the ${\Sigma }^{+}\to p\gamma$ process to illustrate the procedure. We rederive traditional baryon-pole-model results. The calculation indicates the need of some nonleptonic weak interaction with chiral structure different from $\mathrm{}(V-A)\mathrm{}\otimes \mathrm{}(V-A)\mathrm{}$.