Probing CP Violation with Hyperon EDMs at BESIII

TL;DR

This paper reviews recent progress in searching for hyperon electric dipole moments (EDMs) at BESIII, highlighting a significant three-order-of-magnitude improvement in the upper limit for the Lambda hyperon EDM, which probes CP violation beyond the Standard Model.

Contribution

It introduces a novel angular analysis method for entangled hyperon-antihyperon pairs and reports a new, more stringent upper limit on the Lambda hyperon EDM from BESIII data.

Findings

BESIII set a three-order-of-magnitude improved upper limit on Lambda EDM.

The paper develops a formalism linking EDM form factors to angular distributions.

A new modular angular analysis technique enhances sensitivity to hyperon EDMs.

Abstract

The prevalence of matter over antimatter in the observable universe remains one of the most profound puzzles in modern physics, necessitating sources of charge-parity (CP) symmetry violation beyond those incorporated in the Standard Model. While electric dipole moments (EDMs) of elementary particles serve as sensitive probes for such new physics, the hyperon sector has historically remained a largely unexplored territory. This review synthesizes recent advancements in the search for hyperon EDMs, focusing on the novel modular angular analysis of entangled baryon-antibaryon pairs produced in $J/\psi$ decays at electron-positron colliders. We discuss the theoretical formalism connecting the electric dipole form factor to full angular distributions and highlight the recent milestone achieved by the BESIII experiment, which established an improved upper limit on the $\Lambda$ EDM. This result represents a three-order-of-magnitude improvement over historical measurements.