Two-Flavor Chiral Perturbation Theory for Hyperons

TL;DR

This paper develops a two-flavor chiral perturbation theory for hyperons, improving convergence by reducing kaon and eta loop effects, and applies it to baryon masses and axial charges, with potential for lattice QCD analysis.

Contribution

It introduces a reorganized two-flavor chiral expansion for hyperons that addresses convergence issues and incorporates effects of strangeness-changing thresholds.

Findings

Two-flavor theory captures essential hyperon physics with analytic pion mass dependence.

Loop contributions are perturbatively manageable in the two-flavor framework.

Applicable to analyzing pion mass dependence in lattice QCD hyperon data.

Abstract

The three-flavor chiral expansion for octet baryons has well-known problems with convergence. We show that this three-flavor chiral expansion can be reorganized into a two-flavor expansion thereby eliminating large kaon and eta loop contributions. Issues of the underlying formulation are addressed by considering the effect of strangeness changing thresholds on hyperon masses. While the spin-3/2 hyperon resonances are considerably more sensitive to these thresholds compared to the spin-1/2 hyperons, we demonstrate that in both cases the essential physics can be captured in the two-flavor effective theory by terms that are analytic in the pion mass squared, but non-analytic in the strange quark mass. Using the two-flavor theory of hyperons, baryon masses and axial charges are investigated. Loop contributions in the two-flavor theory appear to be perturbatively under control. A natural application for our development is to study the pion mass dependence of lattice QCD data on hyperon properties.