# CP symmetry tests in the cascade-anticascade decay of charmonium

## TL;DR

This paper proposes a method to test CP symmetry in charmonium decays to strange baryons by analyzing angular distributions, enabling separate determination of decay parameters without requiring transverse polarization measurements.

## Contribution

It introduces a novel approach to measure decay parameters and test CP symmetry in charmonium decays to $\Xiar ext{ extLambda}$, utilizing spin correlations in decay chains.

## Key findings

- All decay parameters can be determined separately in vector and scalar charmonia decays.
- Transverse polarization is unnecessary for these measurements.
- The method provides a sensitive test of CP symmetry in the strange baryon sector.

## Abstract

We analyze joint angular distributions of a charmonium decay to the $\Xi\bar\Xi$ pair using the $\Xi\to\Lambda\pi\to p\pi^-\pi$ weak decay chain for the cascade and the charge conjugated mode for the anticascade. The decays allow a direct comparison of the baryon and antibaryon decay properties and a sensitive test of CP symmetry in the strange baryon sector. We show that all involved decay parameters can be determined separately in vector and (pseudo)scalar charmonia decays into $\Xi\bar\Xi$ due to the spin correlations between the weak decay chains. Contrary to the recently measured $e^+e^-\to J/\psi\to \Lambda\bar\Lambda$ process, the transverse polarization of the cascade is not needed and has almost no impact on the uncertainties of the decay parameters.