Karlsruhe 2011 – scientific programme

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T: Fachverband Teilchenphysik

T 36: Top-Produktion I

T 36.3: Talk

Monday, March 28, 2011, 17:15–17:30, 30.22: 130

Estimation of the W+jets background for a tt cross-section measurement in the µ+jets channel with ATLAS detector — Markus Cristinziani, Sara Ghasemi, Gia Khoriauli, •Agnieszka Leyko, Ralph Schäfer, Tatevik Poghosyan, Kirika Uchida, and Kaven Yau — Physikalisches Institut Universität Bonn

W-bosons decaying to muons and neutrinos, together with associated production of jets are the major source of background for the tt cross-section measurement in the µ+jets channel. However it is difficult to model it in Monte-Carlo simulation accurately. Therefore it is of great importance to estimate the rate of this background process directly from data. For this purpose several methods are proposed, such as Berends-Giele scaling or a comparison of the number of W and Z events for different jet multiplicities. These methods are based on the fact that the ratio of cross sections of production of vector boson together with n and n+1 jets is expected to be constant, σ(V+n  jets)/ σ(V+(n+1)  jets)=const.
In this talk different methods for W+jets background estimation will be compared using the full data sample collected by the ATLAS detector in 2010.