CP violation in hyperon nonleptonic decays within the standard model

We calculate the CP-violating asymmetries A(Λ _- ⁰) and A(Ξ _- ^-) in nonleptonic hyperon decay within the standard model using the framework of heavy-baryon chiral perturbation theory ( _χPT). We identify those terms that correspond to previous calculations and discover several errors in the existing literature. We present a new result for the lowest-order (in _χPT) contribution of the penguin operator to these asymmetries, as well as an estimate for the uncertainty of our result that is based on the calculation of the leading nonanalytic corrections.