E2/M1 Mixing Ratio of $\Delta \to N\gamma$ and Hyperon Resonance Radiative Decay

Abstract

We compute the leading contribution to the E2/M1 mixing ratio of the decay $\Delta \to N\gamma$ in heavy baryon chiral perturbation theory. We find the mixing ratio to be $4\%\text{ltap}|{\delta }_{E2/M1}|\text{ltap}11\%$, 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 ${\Sigma }^{\ast +}\to {\Sigma }^{+}\gamma$ and ${\Xi }^{\ast -}\to {\Xi }^{-}\gamma$ provide a particularly sensitive probe of deviations from heavy baryon spin-flavour SU(6).

Comments: Uses harvmac.tex. 9 pages with 2 PostScript figures, packed and included using uufiles and figure. UCSD/PTH 93-04, QUSTH-93-01, Duke-TH-93-47