Studies of the internal properties of jets and jet substructure with the ATLAS Detector

TL;DR

This paper investigates the internal structure of jets at the LHC using the ATLAS detector, measuring various substructure observables, comparing them to simulations, and exploring applications like W boson and top quark identification.

Contribution

It presents the first measurements of filtered jet mass at the LHC and applies new substructure techniques to identify boosted W bosons and top quarks.

Findings

Jet substructure observables agree with Monte Carlo predictions.

First measurement of filtered jet mass at the LHC.

Observation of a W boson mass peak in jet invariant mass spectrum.

Abstract

The internal structure of jets produced in pp collisions at the LHC is measured using the ATLAS detector in an inclusive jet sample corresponding to 35pb-1 of pp collisions at sqrt(s) = 7 TeV. Classical jet shape and energy flow measurements are complemented with measurements of new substructure observables with comparisons made to several leading order parton shower Monte Carlo programs. The jet invariant mass and \kt splitting scale are measured for anti-kt jets with a distance parameter of R=1.0 and Cambridge-Aachen jets with R=1.2. Furthermore, a splitting and filtering procedure is applied to the Cambridge-Aachen jets. These tools are then utilized for the first measurements of the filtered jet mass at the LHC in the inclusive jet sample as well the W+1 jet sample, in which a hadronic W mass peak is observed in the jet invariant mass spectrum. A sample of candidate boosted top quark events is also analyzed in detail for the jet substructure properties of hadronic "top-jets" in the final state.