Testing Bell inequality through h→ττ at CEPC

The decay of Higgs boson into two spin-1/2 particles provides an ideal system to reveal quantum entanglement and Bell-nonlocality. Future e(+)e(-) 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 h ->tau tau at Circular Electron Positron Collider (CEPC). Two realistic methods of testing Bell inequality are investigated, i.e., Tornqvist'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 e(+)e(-)-> Zh. Necessary reconstruction approaches are described to measure quantum entanglement between tau(+) and tau(-). Finally, we show the sensitivity of CEPC to Bell inequality violation for the two methods.