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


Zwalinski L., Zou W., Zormpa O., Zorbas T., Zoch K., Zoccoli A., ...More

European Physical Journal C, vol.85, no.5, 2025 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 85 Issue: 5
  • Publication Date: 2025
  • Doi Number: 10.1140/epjc/s10052-025-14075-3
  • Journal Name: European Physical Journal C
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Chemical Abstracts Core, Communication Abstracts, INSPEC, zbMATH, Directory of Open Access Journals, Nature Index
  • Istanbul University Affiliated: Yes

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. 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%.