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Estimation of backgrounds from jets misidentified as τ-leptons using the Universal Fake Factor method with the ATLAS detector

Aad, G. ; Åkesson, T.P.A. LU orcid ; Astrand, K.S.V. LU ; Doglioni, C. LU ; Ekman, P.A. LU orcid ; Hedberg, V. LU ; Herde, H. LU orcid ; Konya, B. LU ; Lytken, E. LU orcid and Poettgen, R. LU orcid , et al. (2025) In European Physical Journal C 85(12).
Abstract
Processes with τ-leptons in the final state are important for Standard Model measurements and searches for physics beyond the Standard Model. The ATLAS experiment at the Large Hadron Collider observes τ-leptons produced in proton–proton collisions only through their decay products. Data analyses involving hadronically decaying τ-leptons face challenges due to backgrounds from jets misidentified as τ-leptons that are not modelled reliably by Monte Carlo simulations. Data-driven methods such as the fake-factor method allow such misidentified backgrounds to be predicted by measuring transfer factors, known as fake factors, in data from dedicated regions. This paper describes a refined technique for determining the fake factors, the Universal... (More)
Processes with τ-leptons in the final state are important for Standard Model measurements and searches for physics beyond the Standard Model. The ATLAS experiment at the Large Hadron Collider observes τ-leptons produced in proton–proton collisions only through their decay products. Data analyses involving hadronically decaying τ-leptons face challenges due to backgrounds from jets misidentified as τ-leptons that are not modelled reliably by Monte Carlo simulations. Data-driven methods such as the fake-factor method allow such misidentified backgrounds to be predicted by measuring transfer factors, known as fake factors, in data from dedicated regions. This paper describes a refined technique for determining the fake factors, the Universal Fake Factor method. It evaluates the fake factors for a signal region by using fake factors from samples enriched in different sources of jets misidentified as τ-leptons (light-quark, gluon, b-quark, and pile-up jets). Each fake factor is calculated as a linear combination of fake factors measured in these different enriched samples. For the full Run 2 data set, the systematic uncertainty of the calculated fake factors, evaluated using W(μν) enriched event sample, ranges from 15 to 35% depending on the τ-lepton’s transverse momentum and charged-particle decay multiplicity. © CERN for the benefit of the ATLAS Collaboration 2025. (Less)
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type
Contribution to journal
publication status
published
subject
keywords
Bosons, Charged particles, Colliding beam accelerators, Fighter aircraft, Microstrip devices, Monte Carlo methods, ATLAS detectors, ATLAS experiment, Factor methods, Final state, Large Hadron Collider, Large-hadron colliders, Model measurements, Model search, Standard model, The standard model, Intelligent systems, Piles
in
European Physical Journal C
volume
85
issue
12
article number
1441
publisher
Springer Nature
external identifiers
  • scopus:105026654190
ISSN
1434-6044
DOI
10.1140/epjc/s10052-025-14916-1
language
English
LU publication?
yes
id
80204474-3fc4-4598-8c96-64645d8e204a
date added to LUP
2026-04-08 10:36:48
date last changed
2026-04-08 10:37:21
@article{80204474-3fc4-4598-8c96-64645d8e204a,
  abstract     = {{Processes with τ-leptons in the final state are important for Standard Model measurements and searches for physics beyond the Standard Model. The ATLAS experiment at the Large Hadron Collider observes τ-leptons produced in proton–proton collisions only through their decay products. Data analyses involving hadronically decaying τ-leptons face challenges due to backgrounds from jets misidentified as τ-leptons that are not modelled reliably by Monte Carlo simulations. Data-driven methods such as the fake-factor method allow such misidentified backgrounds to be predicted by measuring transfer factors, known as fake factors, in data from dedicated regions. This paper describes a refined technique for determining the fake factors, the Universal Fake Factor method. It evaluates the fake factors for a signal region by using fake factors from samples enriched in different sources of jets misidentified as τ-leptons (light-quark, gluon, b-quark, and pile-up jets). Each fake factor is calculated as a linear combination of fake factors measured in these different enriched samples. For the full Run 2 data set, the systematic uncertainty of the calculated fake factors, evaluated using W(μν) enriched event sample, ranges from 15 to 35% depending on the τ-lepton’s transverse momentum and charged-particle decay multiplicity. © CERN for the benefit of the ATLAS Collaboration 2025.}},
  author       = {{Aad, G. and Åkesson, T.P.A. and Astrand, K.S.V. and Doglioni, C. and Ekman, P.A. and Hedberg, V. and Herde, H. and Konya, B. and Lytken, E. and Poettgen, R. and Smirnova, O. and Wallin, E.J. and Zwalinski, L.}},
  issn         = {{1434-6044}},
  keywords     = {{Bosons; Charged particles; Colliding beam accelerators; Fighter aircraft; Microstrip devices; Monte Carlo methods; ATLAS detectors; ATLAS experiment; Factor methods; Final state; Large Hadron Collider; Large-hadron colliders; Model measurements; Model search; Standard model; The standard model; Intelligent systems; Piles}},
  language     = {{eng}},
  number       = {{12}},
  publisher    = {{Springer Nature}},
  series       = {{European Physical Journal C}},
  title        = {{Estimation of backgrounds from jets misidentified as τ-leptons using the Universal Fake Factor method with the ATLAS detector}},
  url          = {{http://dx.doi.org/10.1140/epjc/s10052-025-14916-1}},
  doi          = {{10.1140/epjc/s10052-025-14916-1}},
  volume       = {{85}},
  year         = {{2025}},
}