Jets and Photons

TL;DR

This paper extends jet concepts to include photons and leptons, integrating jet substructure techniques to improve photon and photon-jet identification and reduce background fakes in high-energy physics analyses.

Contribution

It introduces a unified jet framework encompassing photons, electrons, and unconventional objects like photon-jets, enhancing identification methods with substructure techniques.

Findings

Jet substructure techniques reduce QCD-jet fake rate by factors of 2.5 to 4.

Photon-jet fakes are reduced by factors of 10 to 10^3 at 80% photon ID efficiency.

The approach unifies traditional and unconventional objects within a single jet-based analysis.

Abstract

This Letter applies the concept of `jets', as constructed from calorimeter cell four-vectors, to jets composed (primarily) of photons (or leptons). Thus jets become a superset of both traditional objects such as QCD-jets, photons, and electrons, and more unconventional objects such as photon-jets and electron-jets, defined as collinear photons and electrons, respectively. Since standard objects such as single photons become a subset of jets in this approach, standard jet substructure techniques are incorporated into the photon finder toolbox. We demonstrate that, for a single photon identification efficiency of 80% or above, the use of jet substructure techniques reduces the number of QCD-jets faking photons by factors of 2.5 to 4. Depending on the topology of the photon-jets, the substructure variables reduce the number of photon-jets faking single photons by factors of 10 to 10^3 at a single photon identification efficiency of 80%.