Testing Bell inequality through $h\to\tau\tau$ at CEPC

TL;DR

This paper explores the potential of the Circular Electron Positron Collider (CEPC) to test Bell inequality violations through Higgs boson decays into tau lepton pairs, using realistic simulation methods.

Contribution

It demonstrates the feasibility of testing Bell inequality at CEPC via $h o au au$ decay using two different methods, accounting for detector effects and reconstruction techniques.

Findings

CEPC can potentially observe Bell inequality violation in Higgs decays.

Two methods, T"{o}rnqvist's and CHSH, are effective for testing quantum entanglement.

Simulation shows measurable sensitivity to Bell inequality violation at CEPC.

Abstract

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 $h\to \tau\tau$ at Circular Electron Positron Collider (CEPC). Two realistic methods of testing Bell inequality are investigated, i.e., T\"{o}rnqvist's method and Clauser-Home-Shimony-Holt (CHSH) inequality. In the simulation, we take into account the detector effects of CEPC including uncertainties for tracks and jets from $Z$ boson in the production of $e^+e^-\to Zh$. Necessary reconstruction approaches are described to measure quantum entanglement between $\tau^+$ and $\tau^-$. Finally, we show the sensitivity of CEPC to the Bell inequality violation for the two methods.