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

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Article number238
<mark>Journal publication date</mark>05/2016
<mark>Journal</mark>European Physical Journal C: Particles and Fields
Issue number5
Volume76
Number of pages33
<mark>State</mark>Published
<mark>Original language</mark>English

Abstract

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′→WZ for bosons in the transverse momentum range 200 GeV <pT<<pT< 400 GeV in √s=8 TeV pp collisions with the ATLAS detector at the LHC. For Z-boson tagging efficiencies of ϵZ=90, 50, and 10%, one can achieve W+ -boson tagging rejection factors (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 pT, hadronically decaying Z bosons. However, the modelling of the tagger inputs for boosted W bosons is studied in data using a tt¯-enriched sample of events in 20.3 fb−1 of data at √s=8 TeV. The inputs are well modelled within uncertainties, which builds confidence in the expected tagger performance.