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# A study of tau lepton production in tt events with ATLAS at the LHC

Collins, Neil J (2011)
Ph.D. thesis, University of Birmingham.

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## Abstract

A method is discussed for measuring the tt cross section from tau + jets events in early ATLAS data. Multivariant techniques were avoided in favour of simple cuts and the analysis was applied to 26.4pb$$^-$$$$^1$$of 2010 data. A cut and count technique was used to estimate the number of tt events in a window around the hadronic top mass peak. Subtraction of QCD background from data was performed by scaling events from a QCD enriched sample by the ratio of events in a sideband region. With the current dataset a statistical error is expected of the order of 400% and a measurement is not feasible at this stage. The systematic error on the tt selection eciency was estimated to be 50%. Simple luminosity scaling established that a measurement should become possible within the 2011-2013 LHC run. Once ATLAS has collected between 1 fb$$^-$$$$^1$$ and 3 fb$$^-$$$$^1$$ of data a fractional error of 20% on the expected number of signal events could be achieved. Suggestions are made for reducing the systematic uncertainty on the tt eciency.

Type of Work: Ph.D. thesis. Watson, Alan Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Physics and Astronomy QC Physics University of Birmingham 1746
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