|ΔI|=3/2 decays of the Ω− in chiral perturbation theory

We study the decays Ω−→Ξπ using heavy-baryon chiral perturbation theory to quantify the |ΔI|=1/2 rule in these decay modes. The ratio of |ΔI|=3/2 to |ΔI|=1/2 amplitudes is somewhat larger in these decays than it is in other hyperon decays. At leading order there are two operators responsible for the |ΔI|=3/2 parts of the Ω− decays which also contribute at one loop to other hyperon decays. These one-loop contributions are sufficiently large to indicate (albeit not definitely) that the measured ratio Γ(Ω−→Ξ0π−)/Γ(Ω−→Ξ−π0)≈2.7 may be too large.