Abstract

This paper describes a study of techniques for identifying Higgs bosons at high transverse momenta decaying into bottom-quark pairs, H rightarrow bbar{b}, for proton–proton collision data collected by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy sqrt{s}=13 text {TeV}. These decays are reconstructed from calorimeter jets found with the anti-k_{t}R = 1.0 jet algorithm. To tag Higgs bosons, a combination of requirements is used: b-tagging of R = 0.2 track-jets matched to the large-R calorimeter jet, and requirements on the jet mass and other jet substructure variables. The Higgs boson tagging efficiency and corresponding multijet and hadronic top-quark background rejections are evaluated using Monte Carlo simulation. Several benchmark tagging selections are defined for different signal efficiency targets. The modelling of the relevant input distributions used to tag Higgs bosons is studied in 36 fb^{-1} of data collected in 2015 and 2016 using grightarrow bbar{b} and Z(rightarrow bbar{b})gamma event selections in data. Both processes are found to be well modelled within the statistical and systematic uncertainties.

Highlights

  • In order to identify, or tag, boosted Higgs bosons it is paramount to understand the details of b-hadron identification and the internal structure of jets, or jet substructure, in sinucthhiasnpaepnveririosnbmuielnt to[n1s1t]u.dTiehsefarpopmroLaHchCtorutnagsgaitn√gspr=ese7natnedd and for discrimination of Z bosons from W bosons [15].Gluon splitting into has been studied at b√-qs ua=rk 1p3aiTrseVat small opening angles by ATLAS [16]

  • Different working point (WP) (60%, 70%, 77% and 85%) are studied in the analyses presented in this paper and jets satisfying a particular MV2c10 criterion WP are referred to as ‘b-tagged jets’

  • Techniques to identify Higgs bosons at high transverse momenta decaying into bottom-quark pairs are described in this paper

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Summary

Introduction

Tag, boosted Higgs bosons it is paramount to understand the details of b-hadron identification and the internal structure of jets, or jet substructure, in sinucthhiasnpaepnveririosnbmuielnt to[n1s1t]u.dTiehsefarpopmroLaHchCtorutnagsgaitn√gspr=ese7natnedd. The identification of Higgs bosons at high transverse momenta through the use of jet substructure has been studied by the CMS Collaboration and their techniques are described in. The Higgs boson tagging efficiency and background rejection for the two most common background processes, the multijet and hadronic top-quark backgrounds, are evaluated using Monte Carlo simulation. In particular the modelling of relevant Higgs-jet properties in Monte Carlo simulation is compared with data. 2 and of the data and simulated samples, the object reconstruction, selection and labelling is discussed in Sect. 6. Sections 7 and 8 discuss a comparison between relevant distributions in data control samples dominated by g → bband Z (→ bb)γ and the corresponding simulated events, respectively.

ATLAS detector
Data and simulated event samples
Calorimeter jets
Truth jets
Track-jets
Jet flavour labelling
Track-jet ghost association
Jet labelling
4.10 Large-R jet mass
Large-R jets
Flavour tagging
Higgs-jet tagger
Two-step sample reweighting
Flavour-tagging working points
Mass window optimisation
Jet substructure
Event selection
Flavour fraction corrections
Jet substructure results
Background estimate
Findings
Conclusions
Full Text
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