A new method to distinguish hadronically decaying boostedZbosons fromWbosons using the ATLAS detector

摘要

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' ightarrow WZ) for bosons in the transverse momentum range 200?GeV?(_ ext {T}<)?400?GeV in (sqrt{s}=8) TeV pp collisions with the ATLAS detector at the LHC. For Z-boson tagging efficiencies of (epsilon _Z=90), 50, and (10,%), one can achieve (W^+)-boson tagging rejection factors ((1/epsilon _{W^+})) 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 (p_ ext {T}), hadronically decaying Z bosons. However, the modelling of the tagger inputs for boosted W bosons is studied in data using a (tar{t})-enriched sample of events in 20.3 fb({}^{-1}) of data at (sqrt{s}=8) TeV. The inputs are well modelled within uncertainties, which builds confidence in the expected tagger performance.