Probing Quantum Entanglement in $\ddot{I}{„}^{+}\ddot{I}{„}^{-}$ Pairs via the $\ddot{I}€\ddot{I}€$ Channel at STCF

Abstract

Quantum entanglement and Bell-inequality violation in $\ddot{I}{„}^{+}\ddot{I}{„}^{-}$ pairs provide a sensitive probe of quantum correlations in high-energy interactions. We present a feasibility study of $e^{+}{e}^{-}\to \ddot{I}{„}^{+}\ddot{I}{„}^{-}$ at the proposed Super Tau-Charm Facility based on full Monte Carlo simulation at $\sqrt{s}=7$ GeV, focusing on the $\ddot{I}€\ddot{I}€$ channel ($\ddot{I}{„}^{\pm }\to \ddot{I}{€}^{\pm }\hat{I}½$), which offers the maximal spin-analyzing power $|\hat{I}º|=1$ and the simplest final-state topology for validating the quantum-tomography framework. We establish a consistency chain from the tree-level QED prediction through truth-level and detector-level reconstruction, yielding a reconstructed concurrence of $0.279\pm 0.007$ with the good-solution approach. A complementary full-simulation study of the $\ddot{I}\ddot{I}$ channel is also briefly reported. These results demonstrate that the STCF can provide a competitive platform for precision studies of quantum correlations in $\ddot{I}„$-lepton pairs.

6 pages, 2 figures. Contribution to the proceedings of the 7th International Workshop on Future Tau-Charm Facilities in hosted by Huangshan University, in Huangshan, China, in Nov. 23 - 27, 2025