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T: Fachverband Teilchenphysik

T 65: Top quarks: differential cross sections

T 65.3: Vortrag

Mittwoch, 1. April 2020, 17:00–17:15, H-HS VIII

Measurements of observables sensitive to color reconnection in tt dilepton events — •Shayma Wahdan¹, Dominic Hirschbühl¹, Wolfgang Wagner¹, Thorsten Kuhl², Andrea Knue³, Frederic Deliot⁴, Tetiana Moskalets⁴, and Clement Helsens⁵ — ¹Wuppertal — ²DESY — ³Freiburg — ⁴Saclay CEA — ⁵CERN

The color reconnection (CR) modelling uncertainty could become one of the dominant sources of systematic uncertainties in the top mass determination. Ongoing top-quark mass analyses use the PYTHIA 8 MC generator for parton showering and hadronization. PYTHIA 8 comes with several alternative CR models which should be explored to estimate the CR modelling uncertainty. At the same time, the models should be confronted with collision data to test their validity. Only models which are in agreement with data in general are suitable to define the corresponding modelling uncertainty. An investigation to find the most discriminating observable between these models has been done in tt dilepton events. The sensitive observables use tracks associated to the vertex of the hard scattering (primary vertex). The selected tracks are still diluted with pile-up tracks and tracks of secondary particles. Therefore, a pile-up model is developed to subtract the pile-up contribution. The observables are then unfolded to the particle level.