Mainz 2014 – scientific programme

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T: Fachverband Teilchenphysik

T 63: Top-Quarks: Paarproduktion

T 63.7: Talk

Tuesday, March 25, 2014, 18:15–18:30, P104

Observables to distinguish BSM Z'->ttbar signal vs QCD/W+jets in leptonic top decay at ATLAS — •Madalina Stanescu-Bellu — DESY, Zeuthen, Deutschland

Searching for new physics in ttbar events requires efficient reconstruction of the top quarks, on a large ttbar mass spectrum. For tops produced at low energies, the decay products are well separated (resolved). The tops produced through a heavy resonance are boosted in pT and their decay products are collimated in a narrow cone, forming a mono-jet topology with substructure. The main challenge is to distinguish the top mono-jets from SM background, such as QCD di-jets and W+jets: hadronically decaying tops (q+q'+b) by the jet substructure; leptonically decaying tops (l+b+nu) by the lepton embedded in a leptonic top mono-jet. Some observables distinguish as well events with prompt (good) muons vs decay muons within the same Z'->ttbar signal samples. Also the energy corrections are investigated, that are needed to ballance the leptonic top mono-jet with the hadronic top mono-jet.