Improved reconstruction of highly boosted τ -lepton pairs in the ττ RIGHTWARDS ARROW (μνμντ )(hadrons + ντ ) decay channels with the ATLAS detector

Abstract

This paper presents a new τ -lepton reconstructionand identification procedure at theATLASdetector at theLargeHadron Collider,which leads to significantly improvedperformance in the case of physics processes where a highlyboosted pair of τ -leptons is produced and one τ -leptondecays into a muon and two neutrinos (τμ), and the otherdecays into hadrons and one neutrino (τhad). By removing themuon information from the signals used for reconstructionand identification of the τhad candidate in the boosted pair,the efficiency is raised to the level expected for an isolatedτhad. The new procedure is validated by selecting a sample ofhighly boosted Z RIGHTWARDS ARROW τμτhad candidates from the data sampleof 140 fb-1 of proton-proton collisions at 13 TeV recordedwith the ATLAS detector. Good agreement is found betweendata and simulation predictions in both the Z RIGHTWARDS ARROW τμτhad signalregion and in a background validation region. The resultspresented in this paper demonstrate the effectiveness of theτhad reconstruction with muon removal in enhancing the signalsensitivity of the boosted τμτhad channel at the ATLAS detector.