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

Summary, in English

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. A dedicated treatment attempting to tag the τ-lepton pair as a single object is required. 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 Zγ 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 139fb-1. The resulting data-to-simulation scale factors are close to unity with uncertainties ranging from 26 to 37%. © The Author(s) 2025.

• Author: G. Aad; T.P.A. Åkesson; K.S.V. Astrand; C. Doglioni; P.A. Ekman; V. Hedberg; H. Herde; B. Konya; E. Lytken; R. Poettgen; O. Smirnova; E.J. Wallin; L. Zwalinski
• Department/s: Particle and nuclear physics; eSSENCE: The e-Science Collaboration; Department of Physics
• Publishing year: 2025
• Language: English
• Publication/Series: European Physical Journal C
• Volume: 85
• Issue: 5
• Links: http://dx.doi.org/10.1140/epjc/s10052-025-14075-3
• Document type: Journal article
• Publisher: Springer Nature
• Topic: Subatomic Physics
• Keywords: ATLAS detectors; Boosted decision trees; Decay products; Identification algorithms; Lepton pairs; Performance; QCD jets; Reconstruction algorithms; Single object; Transverse momenta; Colliding beam accelerators
• Status: Published
• ISBN/ISSN/Other: ISSN: 1434-6044