Power Counting to Better Jet Observables

Abstract

Optimized jet substructure observables for identifying boosted topologies will play an essential role in maximizing the physics reach of the Large Hadron Collider. Ideally, the design of discriminating variables would be informed by analytic calculations in perturbative QCD. Unfortunately, explicit calculations are often not feasible due to the complexity of the observables used for discrimination, and so many validation studies rely heavily, and solely, on Monte Carlo. In this paper we show how methods based on the parametric power counting of the dynamics of QCD, familiar from effective theory analyses, can be used to design, understand, and make robust predictions for the behavior of jet substructure variables. As a concrete example, we apply power counting for discriminating boosted Z bosons from massive QCD jets using observables formed from the n-point energy correlation functions. We show that power counting alone gives a definite prediction for the observable that optimally separates the background-rich from the signal-rich regions of phase space. Power counting can also be used to understand effects of phase space cuts and the effect of contamination from pile-up, which we discuss. As these arguments rely only on the parametric scaling of QCD, the predictions from power counting must be reproduced by any Monte Carlo, which we verify using Pythia8 and Herwig++. We also use the example of quark versus gluon discrimination to demonstrate the limits of the power counting technique.

35 pages, 15 figures

References in corpus (12)

• PYTHIA 6.4 Physics and Manual
• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• Herwig++ Physics and Manual
• Jet substructure as a new Higgs search channel at the LHC
• Pileup Per Particle Identification
• Boosted objects: a probe of beyond the Standard Model physics
• Jet mass and substructure of inclusive jets in sqrt(s) = 7 TeV pp collisions with the ATLAS experiment
• Pileup subtraction for jet shapes
• Resummation of heavy jet mass and comparison to LEP data
• On jet mass distributions in Z+jet and dijet processes at the LHC
• Particle-level pileup subtraction for jets and jet shapes
• Precision Jet Substructure from Boosted Event Shapes

Cited by in corpus (18)

• New Angles on Energy Correlation Functions
• The Collinear Limit of the Energy-Energy Correlator
• Parton Shower Uncertainties in Jet Substructure Analyses with Deep Neural Networks
• Resummation of Double-Differential Cross Sections and Fully-Unintegrated Parton Distribution Functions
• Search for diboson resonances with boson-tagged jets in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Quark-Gluon tagging with Shower Deconstruction: Unearthing dark matter and Higgs couplings
• Soft evolution of multi-jet final states
• Search for heavy resonances decaying to a $W$ or $Z$ boson and a Higgs boson in the $q{\bar{q}}^{(\prime )}b\bar{b}$ final state in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• The Analytic Structure of Non-Global Logarithms: Convergence of the Dressed Gluon Expansion
• Search for dark matter produced in association with a hadronically decaying vector boson in pp collisions at $\sqrt{s}$=13 TeV with the ATLAS detector
• Towards Machine Learning Analytics for Jet Substructure
• Collinear expansion for color singlet cross sections
• An Optimal Observable for Color Singlet Identification
• Cutting Multiparticle Correlators Down to Size
• The importance of calorimetry for highly-boosted jet substructure
• On Statistical Aspects of Qjets
• Perspectives and Outlook from HEP Window on the Universe
• Traces of a triboson resonance