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.

Estimation of backgrounds from jets misidentified as $$\tau $$-leptons using the Universal Fake Factor method with the ATLAS detector / Aad, G., Aakvaag, E., Abbott, B., Abdelhameed, S., Abeling, K., Abicht, N.J., Abidi, S.H., Aboelela, M., Aboulhorma, A., Abramowicz, H., Abulaiti, Y., Acharya, B.S., Ackermann, A., Adam Bourdarios, C., Adamczyk, L., Addepalli, S.V., Addison, M.J., Adelman, J., Adiguzel, A., Adye, T., et al.. - In: EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6052. - 85:12(2025). [10.1140/epjc/s10052-025-14916-1]

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

Aloisio, A.;Alviggi, M.;Canale, V.;Cirotto, F.;D'Avanzo, A.;Della Pietra, M.;Massarotti, P.;Rossi, E.;
2025

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.
2025
Estimation of backgrounds from jets misidentified as $$\tau $$-leptons using the Universal Fake Factor method with the ATLAS detector / Aad, G., Aakvaag, E., Abbott, B., Abdelhameed, S., Abeling, K., Abicht, N.J., Abidi, S.H., Aboelela, M., Aboulhorma, A., Abramowicz, H., Abulaiti, Y., Acharya, B.S., Ackermann, A., Adam Bourdarios, C., Adamczyk, L., Addepalli, S.V., Addison, M.J., Adelman, J., Adiguzel, A., Adye, T., et al.. - In: EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6052. - 85:12(2025). [10.1140/epjc/s10052-025-14916-1]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/1047694
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