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arXiv:2605.01233

Probing Quantum Entanglement in $τ^+τ^-$ Pairs via the $ππ$ Channel at STCF

Xiaokang Li, Chentao Bao, Hai Chen, Mingyi Liu, Dayong Wang

hep-exhep-phquant-phSubmitted May 2, 2026• Announced May 5, 2026• Revised Jun 2, 2026 (v2)
v1 · May 2, 2026v2 · Jun 2, 2026
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Abstract

Quantum entanglement and Bell-inequality violation in $τ^+τ^-$ pairs provide a sensitive probe of quantum correlations in high-energy interactions. We present a feasibility study of $e^+e^- \to τ^+τ^-$ at the proposed Super Tau-Charm Facility based on full Monte Carlo simulation at $\sqrt{s} = 7$ GeV, focusing on the $ππ$ channel ($τ^\pm \to π^\pmν$), which offers the maximal spin-analyzing power $|κ| = 1$ 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 $ρρ$ channel is also briefly reported. These results demonstrate that the STCF can provide a competitive platform for precision studies of quantum correlations in $τ$-lepton pairs.

DOI
10.1142/S0217751X26450028
Comments
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

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