Testing Bell inequality through at CEPC* *Tong Li is Supported by the National Natural Science Foundation of China (12375096, 12035008, 11975129), and "the Fundamental Research Funds for the Central Universities", Nankai University (63196013). Kai Ma was supported by the Natural Science Basic Research Program of Shaanxi Province, China (2023-JC-YB-041) and the Innovation Capability Support Program of Shaanxi Province, China (2021KJXX-47)

Abstract

The decay of Higgs boson into two spin-1/2 particles provides an ideal system to reveal quantum entanglement and Bell-nonlocality. Future colliders can improve the measurement accuracy of the spin correlation of tau lepton pairs from Higgs boson decay. We show the testability of Bell inequality through at Circular Electron Positron Collider (CEPC). Two realistic methods of testing Bell inequality are investigated, i.e., Törnqvist's method and Clauser-Home-Shimony-Holt (CHSH) inequality. In the simulation, we consider the detector effects of CEPC including uncertainties for tracks and jets from Z boson in the production of . Necessary reconstruction approaches are described to measure quantum entanglement between and . Finally, we show the sensitivity of CEPC to Bell inequality violation for the two methods.