Abstract
This paper describes the trigger and offline reconstruction, identification and energy calibration algorithms for hadronic decays of tau leptons employed for the data collected from pp collisions in 2012 with the ATLAS detector at the LHC center-of-mass energy sqrt{mathrm {s}} = 8 ,hbox {TeV}. The performance of these algorithms is measured in most cases with Z decays to tau leptons using the full 2012 dataset, corresponding to an integrated luminosity of 20.3 fb^{-1}. An uncertainty on the offline reconstructed tau energy scale of 2–4 %, depending on transverse energy and pseudorapidity, is achieved using two independent methods. The offline tau identification efficiency is measured with a precision of 2.5 % for hadronically decaying tau leptons with one associated track, and of 4 % for the case of three associated tracks, inclusive in pseudorapidity and for a visible transverse energy greater than 20 ,hbox {GeV}. For hadronic tau lepton decays selected by offline algorithms, the tau trigger identification efficiency is measured with a precision of 2–8 %, depending on the transverse energy. The performance of the tau algorithms, both offline and at the trigger level, is found to be stable with respect to the number of concurrent proton–proton interactions and has supported a variety of physics results using hadronically decaying tau leptons at ATLAS.
Highlights
With a mass of 1.777 GeV and a proper decay length of 87 μm [1], tau leptons decay either leptonically
The efficiency of the identification and the energy scale are measured in dedicated studies using a Z → τ τ -enhanced event sample of collision data recorded by the ATLAS detector [20] at the LHC [21] in 2012 at a centre-of-mass energy of 8 TeV
In the fit to extract the efficiencies for real tau leptons passing different levels of identification, the ratio of jet to other τhad-vis candidates is determined in a preselection step and extrapolated to regions where identification is required by using jet misidentification rates determined in an independent data sample
Summary
With a mass of 1.777 GeV and a proper decay length of 87 μm [1], tau leptons decay either leptonically The main background to hadronic tau lepton decays is from jets of energetic hadrons produced via the fragmentation of quarks and gluons This background is already present at trigger level ( referred to as online in the following). 5. The efficiency of the identification and the energy scale are measured in dedicated studies using a Z → τ τ -enhanced event sample of collision data recorded by the ATLAS detector [20] at the LHC [21] in 2012 at a centre-of-mass energy of 8 TeV. The efficiency of the identification and the energy scale are measured in dedicated studies using a Z → τ τ -enhanced event sample of collision data recorded by the ATLAS detector [20] at the LHC [21] in 2012 at a centre-of-mass energy of 8 TeV
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