Karlsruhe 2011 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 36: Top-Produktion I

T 36.2: Vortrag

Montag, 28. März 2011, 17:00–17:15, 30.22: 130

Muon trigger efficiency and scale factors for semi-leptonic tt decays — •Valentina Ferrara — Humboldt University, Berlin, Germany

The fist step towards measuring the tt production cross-section is the selection of good signal candidates. The total efficiency of this selection is the combination of reconstruction. identification and trigger efficiencies. These have to be measured with the smallest possible uncertainty. For the selection of semi-leptonic tt events decaying in the muon channel we are relying on muon triggers. The trigger efficiency is the fraction of triggered events with respect to all events satisfying the trigger requirements and can be calculated from simulation. To measure muon trigger efficiencies directly from data, ATLAS has adopted the data-driven Tag&Probe method that makes use of double-object final states, such as Z→µµ. Then, the ratio between the trigger efficiency measured with data and Monte Carlo is performed. The resulting scale factor is the final correction factor used to scale the Monte Carlo trigger efficiency to make it fit the data. Studies concerning the calculation of the scale factors as a function of different parameters for various ATLAS muon triggers and their extrapolation to tt events are presented.