Reconstruction and identification of pairs of collimated $\tau$-leptons decaying hadronically using $\sqrt{s}=13$ TeV $pp$ collision data with the ATLAS detector

Abstract

This paper describes an algorithm for reconstructing and identifying a highly collimated hadronically decaying $\tau$-lepton pair with low transverse momentum. When two $\tau$-leptons are highly collimated, their visible decay products might overlap, degrading the reconstruction performance for each of the $\tau$-leptons. This requires a dedicated treatment that attempts to tag it as a single object. The reconstruction algorithm is based on a large radius jet and its associated two leading subjets, and the identification uses a boosted decision tree to discriminate between signatures from ${\tau }^{+}{\tau }^{-}$ systems and those arising from QCD jets. The efficiency of the identification algorithm is measured in $Z\gamma$ events using proton-proton collision data at $\sqrt{s}=13$ TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 $\mbox{fb}^{-1}$. The resulting data-to-simulation scale factors are close to unity with uncertainties ranging from 26% to 37%.

49 pages in total, author list starting page 32, 10 figures, 5 tables, published in Eur. Phys. J. C 85 (2025) 561. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TAUP-2020-03/

References in corpus (10)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• New parton distributions for collider physics
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Singlet Higgs Phenomenology and the Electroweak Phase Transition
• Collider Probes of Axion-Like Particles
• A Renormalizable Model for the Galactic Center Gamma Ray Excess from Dark Matter Annihilation
• Nonstandard Higgs Boson Decays
• Search for a light pseudoscalar Higgs boson in the boosted $\mu \mu \tau \tau$ final state in proton-proton collisions at $\sqrt{s}=$ 13 TeV