Wuppertal 2015 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
T: Fachverband Teilchenphysik
T 21: Top: tt+2 Photonen, tt+Z
T 21.4: Vortrag
Montag, 9. März 2015, 17:30–17:45, L.09.31 (HS 11)
Studies on ttZ→ 4 ℓ production in 8 TeV proton-proton collisions with the ATLAS detector — Volker Büscher1, Markus Cristinziani2, Evan Machefer2, Carsten Meyer1, Liza Mijović2, Alexandra Schulte1, and •Kaven Yau Wong2 — 1JGU Mainz — 2Physikalisches Institut, Universität Bonn
The associated production of a top-quark pair and a Z boson is a rare process which can be used to directly measure the tZ coupling. With a theoretical cross section at NLO of 0.206 pb, around 4200 events are expected to have been produced from the proton-proton collisions at a center-of-mass energy of 8 TeV at LHC in 2012. The data collected by the ATLAS detector amount to 20.3 fb−1. The final state with four leptons (4ℓ) has a small branching ratio, with only 20 events expected to have been produced in the whole 2012 run, but this small branching ratio is compensated by the high event purity that can be achieved due to its rare signature.
This talk will present the event selection and the estimation of the contribution from events with at least one fake lepton. The event selection used is a compromise between high purity and a reasonable number of expected events. This is achieved using five different signal regions based on the number of b-tagged jets and lepton flavour composition. The contribution from events with at least one fake lepton is estimated using data-driven methods, more specifically, using an ABCD method.
Other details of this analysis will be discussed in the talk by Alexandra Schulte.