Abstract

These proceedings describe the reconstruction and identification of tau leptons in the ATLAS experiment at the LHC. Tau leptons play an important role in the measurement of Standard Model processes, in the search for new physics (Supersymmetry, heavy resonances) and in the measurement of Higgs boson properties. Hadronic tau lepton decays are reconstructed calorimeter based and separation against QCD-induced jets is done relying on shapes of energy depositions in the calorimeter as well as tracking based variables. The energy scale of tau leptons is obtained by scaling the measured momentum to the simulated one and is cross-checked in data. The tau trigger makes use of the collimated nature of tau decays and relies on a combination of objects (e.g. tau + muon) to reduce the rates and thresholds. An outlook to the improved tau reconstruction to be used in the next data-taking period of ATLAS concludes the proceedings.

Highlights

  • Tau leptons play an important role in the physics programme of the ATLAS experiment [1] at the LHC [2]

  • In addition to separation against jets, the identification separates hadronic taus from electrons and from muons (by vetoing tau candidates (a) in analyses that overlap with muons and (b) with very high or low electromagnetic fractions) [7]

  • The first level relies on so-called trigger towers, which are the sums of calorimeter cells across layers, such that their size is about ∆η×∆φ = 0.1×0.1

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Summary

Introduction

Tau leptons play an important role in the physics programme of the ATLAS experiment [1] at the LHC [2]. The tau lepton decays hadronically (≈ 65%) and leptonically (≈ 35%). Hadronic decays are considered in the tau reconstruction. Hadronic tau decays are classified into 1prong and 3-prong decays, which contain one and three charged particles, respectively. Every tau decay contains a tau neutrino, so that only the visible tau energy can be measured and the true energy is not accessible. All decay products are collimated, due to the boost of the tau lepton. The main background to tau leptons are QCD induced jets. In contrast to hadronic tau decays, their particle multiplicity increases with the energy of the jet and they are typically wider.

Reconstruction and Identification of Tau Leptons
Tau Energy Scale
Trigger
Prospects for 2015 and beyond
Findings
20 GeV tau trigger
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