Karlsruhe 2024 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 23: Top physics 1
T 23.3: Vortrag
Montag, 4. März 2024, 16:30–16:45, Geb. 30.95: Audimax
Measurements of Top-quark Pair Spin Correlation in the ℓ + Jets Channel Using the ATLAS Experiment — •Oleksandr Burlayenko1, Andrea Knue2, and Zuzana Rurikova1 — 1University of Freiburg — 2TU Dortmund
The top quark, the heaviest known fundamental particle exhibits a lifetime of O(10−25s), which is shorter than both the quantum chromodynamic (QCD) hadronization time scale 1/ΛQCD≈ 10−24s and the spin decorrelation time scale mt/ΛQCD2≈10−21s. This allows studying the spin properties of a bare quark, as the angular distribution of its decay products preserves its spin information.
Within the Standard Model (SM), tt pairs have correlated spins, with the degree of correlation being sensitive to the production mechanism. The most recent measurement performed by ATLAS uses 13 TeV data in the dilepton channel.
This work presents ongoing studies of the tt spin correlation in the ℓ + jet channel at √s=13 TeV. While this channel provides a larger dataset, the analyzing power is reduced compared to the dilepton channel.
To improve event reconstruction, machine learning techniques are employed. Combined with an optimization study, these techniques exhibit high performance in eliminating non-reconstructable events. Furthermore, the measurement of SM-like spin correlation in a blinded Asimov profile likelihood template fit will be presented, considering the full impact of systematic uncertainties and various spin correlation sensitive observables.
Keywords: top quark; spin correlation; tt pair; 13 TeV