******** 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.