Improved reconstruction of highly boosted $$\tau $$-lepton pairs in the $$\tau \tau \rightarrow (\mu \nu _{\mu }\nu _{\tau })(\text {hadrons}+\nu _{\tau })$$ decay channels with the ATLAS detector

UNSPECIFIED (2025) Improved reconstruction of highly boosted $$\tau $$-lepton pairs in the $$\tau \tau \rightarrow (\mu \nu _{\mu }\nu _{\tau })(\text {hadrons}+\nu _{\tau })$$ decay channels with the ATLAS detector. European Physical Journal C: Particles and Fields, 85 (6): 706. ISSN 1434-6044

Abstract

This paper presents a new $$\tau $$ τ -lepton reconstruction and identification procedure at the ATLAS detector at the Large Hadron Collider, which leads to significantly improved performance in the case of physics processes where a highly boosted pair of $$\tau $$ τ -leptons is produced and one $$\tau $$ τ -lepton decays into a muon and two neutrinos ( $$\tau _\mathrm {\mu }$$ τ μ ), and the other decays into hadrons and one neutrino ( $$\tau _\textrm{had}$$ τ had ). By removing the muon information from the signals used for reconstruction and identification of the $$\tau _\textrm{had}$$ τ had candidate in the boosted pair, the efficiency is raised to the level expected for an isolated $$\tau _\textrm{had}$$ τ had . The new procedure is validated by selecting a sample of highly boosted $$Z\rightarrow \tau _\mathrm {\mu }\tau _\textrm{had}$$ Z → τ μ τ had candidates from the data sample of 140 $$\textrm{fb}^{-1}$$ fb - 1 of proton–proton collisions at 13 TeV recorded with the ATLAS detector. Good agreement is found between data and simulation predictions in both the $$Z\rightarrow \tau _\mathrm {\mu }\tau _\textrm{had}$$ Z → τ μ τ had signal region and in a background validation region. The results presented in this paper demonstrate the effectiveness of the $$\tau _\textrm{had}$$ τ had reconstruction with muon removal in enhancing the signal sensitivity of the boosted $$\tau _\mathrm {\mu }\tau _\textrm{had}$$ τ μ τ had channel at the ATLAS detector.