******** Special Seminar ********

Speaker ：Prof. Shih-Chieh Hsu (UW-Seattle)

Title ：Machine Learning Probes of τ⁺τ⁻ Entanglement at the LHC

Time ：10:30-12:30, Tuesday, 2026/1/6

Place ：P512, 5F, 3rd General Building, Nat'l Tsing Hua Univ.

Abstract:
The Large Hadron Collider (LHC) provides a unique arena for exploring quantum correlations in high-energy processes beyond traditional tests of the Standard Model. In this study, we investigate the quantum entanglement and Bell nonlocality of τ⁺τ⁻ pairs produced in proton-proton collisions. Leveraging detailed Monte Carlo simulations of the process pp → τ⁺τ⁻ X, we perform full quantum state tomography of the di-τ spin system. Reconstructing the neutrino momenta—typically the main experimental challenge in τ decays—using advanced machine learning algorithms enables precise determination of the τ⁺τ⁻ spin density matrix. This method significantly improves sensitivity to spin correlations and allows a direct test of Bell-type inequalities in the high-energy regime. Our results demonstrate a statistically significant ( > 5σ ) violation of Bell inequalities, establishing τ⁺τ⁻ as a promising system for probing quantum information phenomena within quantum field theory. The approach opens a pathway to studying entanglement, decoherence, and CP-violating effects in other heavy-flavor and electroweak processes. We propose that the τ⁺τ⁻ system should serve as a new benchmark for quantum information studies in collider environments, complementing the widely explored t t̄ channel and bridging quantum theory, particle phenomenology, and machine learning.