Estimation of background for final states including tau leptons with the ATLAS experiment

Abstract

Processes with tau leptons in a final state are essential in many experi- ments studying products of proton collisions. Tau lepton most often decays hadronically; therefore jets misidentified as tau leptons can be a source of a significant part of the background of these events. A part of phase space where most reconstructed taus are misidentified jets is chosen. This part of phase space can be events with Z boson decaying into two muons. These events were studied, and distributions of several variables were compared with Monte Carlo simulation. A second part of the thesis presents studies based on a subsample of these events, consisting of events with an addi- tional jet passing specific loose tau lepton selection criteria. A data-driven method for estimating this type of background, fake factor, was studied on these events. 1