Heidelberg 2022 – scientific programme
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T: Fachverband Teilchenphysik
T 7: Top Quarks: Properties 1
T 7.6: Talk
Monday, March 21, 2022, 17:30–17:45, T-H20
Measurement of top-quark pair spin correlation in the ℓ + jets channel using the ATLAS experiment — •Oleksandr Burlayenko, Andrea Knue, and Zuzana Rurikova — Albert-Ludwigs Universität Freiburg, Experimentelle Teilchenphysik AG Herten
The top quark is the heaviest known fundamental particle and has a lifetime on the order of 10−25 s. This lifetime is shorter than the quantum chromodynamic (QCD) hadronization time scale 1 / ΛQCD ≈ 10−24 s, and much shorter than the spin decorrelation time scale mt / ΛQCD2 ≈ 10−21 s. This gives an opportunity to study the spin properties of a bare quark, as top-quark spin information is preserved in the angular distribution of its decay products.
The Standard Model predicts the tt pairs to have correlated spins. The degree of the this correlation is sensitive to the production mechanism of the top quark. The ATLAS collaboration measured it at 13 TeV in the dilepton channel. In this measurement, a discrepancy between the predicted and observed results was found.
This work presents ongoing studies of the tt spin correlation in the lepton + jet channel at √s=13 TeV. While this channel provides a larger dataset to study, the analyzing power is reduced compared to the dilepton channel. In this talk, first studies will be presented including different event selections and different observables for this final state.