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

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 $W^{\prime }\to WZ$ for bosons in the transverse momentum range 200 GeV $<p_T<$ 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 $p_T$, hadronically decaying $Z$ bosons. However, the modelling of the tagger inputs for boosted $W$ bosons is studied in data using a $t\bar{t}$-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.

32 pages plus author list (49 pages total), 19 figures, published version, all figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/PERF-2015-02/

References in corpus (14)

• PYTHIA 6.4 Physics and Manual
• Big-Bang Nucleosynthesis
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• New parton distributions for collider physics
• Herwig++ Physics and Manual
• Single-top hadroproduction in association with a W boson
• The Catchment Area of Jets
• Colour reconnections in Herwig++
• Jet mass and substructure of inclusive jets in sqrt(s) = 7 TeV pp collisions with the ATLAS experiment
• Light-quark and gluon jet discrimination in pp collisions at $\sqrt{s}$ = 7 TeV with the ATLAS detector
• Identification techniques for highly boosted W bosons that decay into hadrons
• Measurements of normalized differential cross-sections for ttbar production in pp collisions at sqrt(s) = 7 TeV using the ATLAS detector
• Measurement of the $WW+WZ$ cross section and limits on anomalous triple gauge couplings using final states with one lepton, missing transverse momentum, and two jets with the ATLAS detector at $\sqrt{\mathrm{s}}=7$ TeV
• Jet Charge with the ATLAS Detector using $\sqrt{s}=8$ TeV $pp$ Collision Data

Cited by in corpus (13)

• Jet Substructure at the Large Hadron Collider: A Review of Recent Advances in Theory and Machine Learning
• Jet Substructure at the Large Hadron Collider: Experimental Review
• Performance of top-quark and $W$-boson tagging with ATLAS in Run 2 of the LHC
• Jet Substructure Studies with CMS Open Data
• Boosted $W/Z$ Tagging with Jet Charge and Deep Learning
• Identification of boosted Higgs bosons decaying into $b$-quark pairs with the ATLAS detector at 13 TeV
• Identification of high transverse momentum top quarks in $pp$ collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector
• Maximum performance of strange-jet tagging at hadron colliders
• Identifying the Quantum Properties of Hadronic Resonances using Machine Learning
• Boosted and semi-boosted all-hadronic $t\bar{t}$ reconstruction performance on kinematic variables for selected BSM models using a 2D extesion of the BumpHunter algorithm
• Study of semi-boosted top quark reconstruction performance on the line shape of a $t\bar{t}$ resonance
• Experimental Impact of Jet Fragmentation Reference Frames At Particle Colliders
• Application of Deep Learning to Jet Charge Discrimination