Light hyperon physics at the BESIII experiment

TL;DR

The BESIII experiment has collected extensive data on hyperons, enabling new tests of CP violation through hyperon polarization measurements and decay analyses at the J/psi and psi' resonances.

Contribution

This paper reports on the recent hyperon polarization observations at BESIII, introducing new methods for CP violation tests in hyperon pair decays at electron-positron colliders.

Findings

Observation of hyperon polarizations at BESIII

Potential for CP violation tests in hyperon decays

Multiple independent CP tests possible in Xi- decay

Abstract

The BESIII experiment at the electron-positron collider BEPCII in Beijing (China) is successfully operating since 2008 and has collected large data samples in the tau-mass region, including the world's largest data samples at the $J/\psi$ and $\psi'$ resonances. The recent observations of hyperon polarizations at BESIII opens a new window for testing CP violation, as it allows for simultaneous production and detection of hyperon and anti-hyperon pair two-body weak decays. The CP-symmetry tests can be performed in processes like e.g. $J/\psi\to\Lambda\bar{\Lambda}$, $J/\psi,\psi'\to\Sigma^+\bar{\Sigma}^-$ and $J/\psi\to\Xi^-\bar{\Xi}^+$. For the $\Xi^-\to\Lambda\pi^-$ decay it is possible to perform three independent CP tests and determine the strong phase and weak phase difference.