Abstract
This article gives an overview of the steps taken in ATLAS to identify hadronically decaying tau leptons and to validate the performance. The tau trigger, the reconstruction and identification algorithms, and the energy calibration are described. The performance is tested with Z→ττ events, collected in 2012 at 8 TeV center-of-mass energy of the LHC. Identification efficiencies are determined both in real data and simulation and differences are expressed in terms of correction factors, with uncertainties below 6%. The uncertainty on the energy scale is measured with two independent methods and found to be less than 4%. All algorithms show good stability against a varying number of simultaneous proton-proton collisions.
Highlights
Tau leptons play an important role in the ATLAS [1] physics program at the LHC [2]
A typical 50 GeV tau lepton travels ≈ 2 mm and decays before it even reaches the first layer of the ATLAS detector
The ATLAS τhad identification methods based on Boosted Decision Trees are working well and provide good discrimination against jets and electrons
Summary
Tau leptons play an important role in the ATLAS [1] physics program at the LHC [2]. Examples are Standard Model analyses, ranging from cross section to polarization measurements [3, 4, 5, 6], and searches for physics beyond the Standard Model [7, 8, 9]. A typical 50 GeV tau lepton travels ≈ 2 mm and decays before it even reaches the first layer of the ATLAS detector. It can only be identified by its decay products. The visible part of the tau lepton decay is composed of one or three charged pions and zero to two neutral pions. This leads to a specific signature used to distinguish the hadronic τ decay from other objects in the detector
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