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

ATLAS Collaboration

doi:10.1140/epjc/s10052-025-14075-3

paper

Reconstruction and identification of pairs of collimated $τ$ -leptons decaying hadronically using $s = 13$ TeV $pp$ collision data with the ATLAS detector

arXiv:2411.09357 · doi:10.1140/epjc/s10052-025-14075-3

Abstract

This paper describes an algorithm for reconstructing and identifying a highly collimated hadronically decaying $τ$ -lepton pair with low transverse momentum. When two $τ$ -leptons are highly collimated, their visible decay products might overlap, degrading the reconstruction performance for each of the $τ$ -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 $τ^{+} τ^{-}$ systems and those arising from QCD jets. The efficiency of the identification algorithm is measured in $Z γ$ events using proton-proton collision data at $s = 13$ 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%.

arXiv comment49 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/

Reconstruction and identification of pairs of collimated τ-leptons decaying hadronically using s​=13 TeV pp collision data with the ATLAS detector

Abstract

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Reconstruction and identification of pairs of collimated $τ$ -leptons decaying hadronically using $s = 13$ TeV $pp$ collision data with the ATLAS detector