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T: Fachverband Teilchenphysik
T 36: Top-Quarks
T 36.1: Talk
Monday, March 24, 2014, 16:45–17:00, P102
A data-driven method for W+jets background estimation in tt events — •Arwa Bannoura — Bergische Universität Wuppertal
W +4 jets is the major background process for the tt semi-leptonic channel and other processes. In this ATLAS analysis a new data driven method to estimate the W+jets background process is introduced. The idea of the method is to use Z+jets events to model W+jets events since these events are similar. Z+jets events are converted by scaling the momentum of the two leptons and letting one lepton fake ETmiss. Event shapes are compared and chosen based on their separation power between W+jets and tt events and their similarity between W+jets and converted Z+jets events. A neural network is trained with tt as signal and converted Z+jets events as background. The neural network output distribution is applied to other backgrounds as well and fitted to data to estimate the number of W+jets events.