Discovered over fifty years ago, the tau lepton is one of the more peculiar elementary particles of the Standard Model. As a third-generation fermion, the tau often has enhanced interactions with beyond the Standard Model physics; additionally, its high mass of 1.7 GeV makes it a key Higgs decay channel. Hadronic decays of the tau lepton occur almost twice as often as leptonic ones and experimentally carry more information about the properties of the particle the tau lepton originates from. As such, the hadronic tau leptons play an important role in the ATLAS physics program. In this talk, I will discuss the strategy employed by the ATLAS experiment to detect, characterize and calibrate hadronic tau leptons. I will review the modern machine learning algorithms employed to distinguish them from QCD jets and identify the various decay modes and discuss the usage of these algorithms in selected ATLAS data analyses. Finally, I will review the challenges of hadronic tau signatures in the ATLAS trigger system.
Quentin Buat is a postdoctoral research fellow at Stony Brook University, working on the ATLAS experiment at CERN. He completed his PhD in 2013 at the Université de Grenoble, France where he searched for physics beyond the Standard Model in high-mass diphoton events at the LHC. Since 2013, Buat has been a research fellow first at Simon Fraser University and then at CERN, where he led the ATLAS group studying Higgs boson couplings to leptons. His current research focuses on measuring the properties of the Higgs boson couplings to leptons as well as leading the ATLAS group responsible for the detection and characterization of hadronically-decaying tau leptons.