E2/M1 Mixing Ratio of $Δ\to Nγ$ and Hyperon Resonance Radiative Decay

Abstract

We compute the leading contribution to the E2/M1 mixing ratio of the decay $Δ\rightarrow Nγ$ in heavy baryon chiral perturbation theory. We find the mixing ratio to be $4\% \ltap |δ_{\rm E2/M1}| \ltap 11\%$, much larger than estimates based on the quark model and other hadronic models. We also compute the mixing ratio for the radiative decay of the hyperon resonances. The decays $Σ^{*+}\rightarrowΣ^+γ$ and $Ξ^{*-}\rightarrowΞ^-γ$ provide a particularly sensitive probe of deviations from heavy baryon spin-flavour SU(6).