Data-driven estimation of fake τ background in Higgs searches in ATLAS

In the ATLAS experiment at the LHC, analyses using reconstructed τ leptons, estimation of backgrounds arising for jets misidentified as hadronically decaying τs becomes a crucial issue. This paper presents two methods, the fully data-driven fake factor method and the semi-data- driven fake rate method. Example of fake factor method in the background modelling of H ± → τν analysis and the fake rate method applied to the search for high mass resonances decaying to ττ, in the τ had τ had channel, are presented. The systematics associated with the methods are also discussed.