CP violation in the hyperon decays Σ→ Nπ

The study of $CP$ violation in hyperon transitions has a long history. In the early 2000s the HyperCP experiment made a major effort to seek $CP$-odd signals in the decay sequence Ξ⁻→Λπ⁻ and Λ→ pπ⁻, which motivated more searches. Most recently the BESIII and LHCb Collaborations have acquired or improved the upper bounds on $CP$ violation in a variety of hyperon nonleptonic processes, including Σ⁺→ nπ⁺ and Σ⁺→ pπ⁰. These measurements have not reached the standard-model level yet, but have stimulated a renewed interest in $CP$-violating new physics in strange-quark decay beyond what is constrained by the parameters ε and ε^ from the kaon sector. In this paper, after updating the standard-model expectations for $CP$-odd observables in the modes Σ^±→ Nπ, we revisit new-physics scenarios that could enhance the corresponding quantities in Λ→ Nπ and Ξ→Λπ and apply them to the Σ^± modes. We find that the $CP$ asymmetries in the latter can be significantly increased over the standard-model expectations, at levels which may be tested in the ongoing BESIII experiment and in future endeavors such as PANDA and the Super Tau Charm Facility.