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T: Fachverband Teilchenphysik

T 88: Top Physics IV

T 88.2: Vortrag

Freitag, 20. März 2026, 09:15–09:30, KH 00.011

Quantum entanglement in top-quark pairs using events with large transverse momentum with the ATLAS detector — •Chiara Deponte and Andrea Knue — Technische Universität Dortmund, Deutschland

Quantum entanglement of top-quark pairs is studied by measuring the full spin density matrix using data recorded with the ATLAS experiment in Run 2. Since top quarks have a very short lifetime, their spin information is transferred to its decay products. The angular distributions of these particles in a helicity-based coordinate system in the t t rest frame are then used to measure the entries of the spin density matrix. After the reconstruction of the full t t event, Profile Likelihood Unfolding is performed to remove detector and reconstruction effects. Entanglement is predicted at the t t production threshold and for high M_{t t}. The presented analysis is performed in a phase-space region with high top-quark velocities and production angles. In this region the expected number of events is low so the analysis is statistically limited. Therefore, the single-lepton channel is used to find a balance between statistical and systematic uncertainties. This talk focuses on studies regarding the size of the jet-related systematic uncertainties.

Keywords: ttbar; lepton+jets; spin correlation; quantum entanglement; jet systematic uncertainties