Resonances in radiative hyperon decays

TL;DR

This paper investigates how baryon resonances influence radiative hyperon decays using chiral perturbation theory, revealing significant effects on decay amplitudes and matching experimental asymmetry measurements.

Contribution

It introduces low lying baryon resonances into the effective chiral theory to compute tree-level decay contributions, providing new insights into decay asymmetries.

Findings

Significant contributions to decay amplitudes from resonances

Large negative asymmetry parameter in Sigma+ decay

Agreement with experimental asymmetry measurement

Abstract

The importance of resonances for the radiative hyperon decays is examined in the framework of chiral perturbation theory. Low lying baryon resonances are included into the effective theory and tree contributions to these decays are calculated. We find significant contributions to both the parity-conserving and parity-violating decay amplitudes and a large negative value for the asymmetry parameter in polarized Sigma^+ -> p gamma is found, in agreement with the experimental result alpha(p Sigma^+) = -0.76 +/- 0.08.