Study of CP violation in hyperon decays at Super Charm-Tau Factories with a polarized electron beam

TL;DR

This paper explores how polarized electron beams at future super charm-tau factories can enhance the precision of CP violation tests in hyperon decays, providing a promising avenue for detecting standard model level CP violation.

Contribution

It introduces a novel approach using polarized electron beams and spin-entangled hyperon pairs to improve CP violation measurements in strange baryon decays.

Findings

Polarized beams significantly improve statistical precision of CP tests.

Spin correlations and polarization effects are crucial for accurate CP violation analysis.

Methodology is promising for observing CP violation at standard model levels.

Abstract

Non-leptonic two-body weak decays of baryons are an important tool to probe the combined charge-conjugation--parity symmetry (CP) violation. We explain why the decays of strange baryons provide complementary information to the decays of kaons. A model-independent parameterization of the non-leptonic decays of the $\Lambda$- and $\Xi$-baryons is reviewed, and the amplitudes are updated according to the latest experimental input. We demonstrate the potential of performing precision tests in strange baryon decays at the next generation electron-positron $J/\psi$ factories with luminosity of $10^{35}$ cm$^{-2}$s$^{-1}$. The copious production of spin-entangled hyperon-antihyperon pairs via the $J/\psi$ resonance allows for a direct comparison of the baryon and antibaryon decay properties. Using analytic approximations and numerical calculations, we study the quantitative impact of spin correlations and polarization in such CP tests. We show that by using a longitudinally-polarized electron beam, the statistical precision of the CP tests can be significantly improved compared to the experiments without polarized beams. Furthermore, we map out further directions for possible improvements, like analysis of incompletely reconstructed events or a combination of the isospin related processes. Altogether, these methods are promising for the observation of a statistically significant CP-violation signal with a strength corresponding to the standard model predictions. Our conclusions should encourage more detailed feasibility studies, including optimisation of the measurement methods and studies of systematic effects. Finally, our results call for an update of the theory predictions with increased precision.