Weak Radiative Hyperon Decays: Questioning the Basics

TL;DR

This paper reviews theoretical approaches to weak radiative hyperon decays, emphasizing the importance of asymmetry measurements in understanding fundamental symmetries and potential violations like Hara's theorem.

Contribution

It highlights the significance of asymmetry measurements in hyperon decays for testing the validity of Hara's theorem and exploring SU(3) symmetry breaking.

Findings

Asymmetry in Xi^0 --> Lambda gamma decay is key to understanding decay mechanisms.

Large negative asymmetry alpha in Sigma^+ --> p gamma challenges existing theories.

Violation of Hara's theorem may be a natural feature of particle physics.

Abstract

Main theoretical approaches to weak radiative hyperon decays are briefly reviewed. It is emphasized that only approaches with great predictive power should be seriously considered when seeking a resolution of the puzzle presented by observed large negative asymmetry alpha (Sigma ^+ --> p gamma). In such cases, asymmetry in the Xi ^0 --> Lambda gamma decay is always large while its sign is positive (negative) if Hara's theorem is violated (satisfied). Measuring this asymmetry is therefore crucial for determining whether the large value of alpha (Sigma ^+ --> p gamma) is due to large SU(3) breaking or to some deeper reason. Some arguments suggesting that violation of Hara's theorem might be a feature of Nature, and hints as to its possible origin are also given.