Performance of jet substructure techniques for large-R jets in proton-proton collisions at sqrt(s) = 7 TeV using the ATLAS detector

TL;DR

This ATLAS study systematically evaluates jet substructure tools for large-R jets at 7 TeV using 2011 data. By comparing anti-$k_T$, Cambridge–Aachen, and $k_T$ clustering with grooming methods mass-drop filtering, trimming, and pruning, the work demonstrates improved jet mass resolution, reduced pile-up sensitivity, and enhanced discrimination between boosted hadronic decays (W/Z/top) and QCD backgrounds. The HEPTopTagger is validated for boosted top quarks, and extensive data–MC comparisons confirm the robustness of calibrations, track-based JMS validations, and subjet energy scale assessments across a wide kinematic range. The results guide configuration choices, highlighting trimming with $p_T$-fraction cut and filtering with mass-drop parameters as reliable options for boosted object analyses in high-luminosity environments.

Abstract

This paper presents the application of a variety of techniques to study jet substructure. The performance of various modified jet algorithms, or jet grooming techniques, for several jet types and event topologies is investigated for jets with transverse momentum larger than 300 GeV. Properties of jets subjected to the mass-drop filtering, trimming, and pruning algorithms are found to have reduced sensitivity to multiple proton-proton interactions, are more stable at high luminosity and improve the physics potential of searches for heavy boosted objects. Studies of the expected discrimination power of jet mass and jet substructure observables in searches for new physics are also presented. Event samples enriched in boosted W and Z bosons and top-quark pairs are used to study both the individual jet invariant mass scales and the efficacy of algorithms to tag boosted hadronic objects. The analyses presented use the full 2011 ATLAS dataset, corresponding to an integrated luminosity of 4.7 +/- 0.1 /fb from proton-proton collisions produced by the Large Hadron Collider at a center-of-mass energy of sqrt(s) = 7 TeV.

Figures (54)

• Figure 1: \ref{['fig:intro:TopptdrWb']} The angular separation between the $W$ boson and $b$-quark in top decays, $t \rightarrow Wb$, as a function of the top-quark transverse momentum ($p_{\rm T}\xspace^{\rm t}$) in simulated PYTHIApythia$Z'\rightarrow t\bar{t}$ ($m_{Z^\prime}\xspace=1.6$ TeV) events. \ref{['fig:intro:Wptdrqq']} The angular distance between the light quark and anti-quark from $t \rightarrow Wb$ decays as a function of the $p_{\rm T}$ of the $W$ boson ($p_{\rm T}\xspace^{W}$). Both distributions are at the generator level and do not include effects due to initial and final-state radiation, or the underlying event.
• Figure 2: Single-jet invariant mass distribution for Cambridge--Aachen ($\mathrm{C/A}$) $R=1.2$ jets in simulated events containing highly boosted hadronically decaying $Z$ bosons before and after the application of a grooming procedure referred to as mass-drop filtering. The technical details of this figure are explained in section \ref{['sec:intro:definitions']}. The normalization of the groomed distribution includes the efficiency of mass-drop filtering with respect to the ungroomed large-$R$ jets for comparison. The local cluster weighting (LCW) calibration scheme is described in section \ref{['sec:recocalib:mccalib']}.
• Figure 3: Diagram depicting the two stages of the mass-drop filtering procedure.
• Figure 4: Diagram depicting the jet trimming procedure.
• Figure 5: Diagram illustrating the pruning procedure.