A new method to distinguish hadronically decaying boosted Z bosons from W bosons using the ATLAS detector

The ATLAS Collaboration

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The distribution of particles inside hadronic jets produced in the decay of boosted W and Z bosons can be used to discriminate such jets from the continuum background. Given that a jet has been identified as likely resulting from the hadronic decay of a boosted W or Z boson, this paper presents a technique for further differentiating Z bosons from W bosons. The variables used are jet mass, jet charge, and a b-tagging discriminant. A likelihood tagger is constructed from these variables and tested in the simulation of W′→WZW′→WZ for bosons in the transverse momentum range 200 GeV <pT<<pT< 400 GeV in s√=8s=8 TeV pp collisions with the ATLAS detector at the LHC. For Z-boson tagging efficiencies of ϵZ=90ϵZ=90 , 50, and 10%10% , one can achieve W+W+ -boson tagging rejection factors ( 1/ϵW+1/ϵW+ ) of 1.7, 8.3 and 1000, respectively. It is not possible to measure these efficiencies in the data due to the lack of a pure sample of high pTpT , hadronically decaying Z bosons. However, the modelling of the tagger inputs for boosted W bosons is studied in data using a tt¯tt¯ -enriched sample of events in 20.3 fb −1−1 of data at s√=8s=8 TeV. The inputs are well modelled within uncertainties, which builds confidence in the expected tagger performance.
Original languageEnglish
Article number238
Pages (from-to)1-33
Number of pages33
JournalEuropean Physical Journal C: Particles and Fields
Early online date28 Apr 2016
Publication statusPublished - May 2016

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