Strong and weak $CP$ tests in sequential decays of polarized ${\Sigma }^0$ hyperons

Abstract

The $J/\psi ,\psi (3686)\to {\Sigma }^0{\bar{\Sigma }}^0$ processes and subsequent decays are studied using the world's largest $J/\psi$ and $\psi (3686)$ data samples collected with the BESIII detector. The strong-$CP$ symmetry is tested in the decays of the ${\Sigma }^0$ hyperons for the first time by measuring the decay parameters, ${\alpha }_{{\Sigma }^0}=-0.0017\pm 0.0021\pm 0.0018$ and ${\bar{\alpha }}_{{\Sigma }^0}=0.0021\pm 0.0020\pm 0.0022$. The weak-$CP$ test is performed in the subsequent decays of their daughter particles $\Lambda$ and $\bar{\Lambda }$. Also for the first time, the transverse polarizations of the ${\Sigma }^0$ hyperons in $J/\psi$ and $\psi (3686)$ decays are observed with opposite directions, and the ratios between the S-wave and D-wave contributions of the $J/\psi ,\psi (3686)\to {\Sigma }^0{\bar{\Sigma }}^0$ decays are obtained. These results are crucial to understand the decay dynamics of the charmonium states and the production mechanism of the ${\Sigma }^0-{\bar{\Sigma }}^0$ pairs.

References in corpus (4)

• Measurement of the permanent electric dipole moment of the neutron
• Observation of $CP$ violation in charm decays
• ${\Sigma }^{+}$ and ${\bar{\Sigma }}^{-}$ polarization in the $J/\psi$ and $\psi (3686)$ decays
• Spin asymmetries and correlations in lambda-pair production through the radiative return method

Cited by in corpus (1)

• Observation of the decay $\psi (3686)\to {\Sigma }^0{\bar{\Sigma }}^0\omega$