XCone: N-jettiness as an Exclusive Cone Jet Algorithm

TL;DR

XCone is a novel jet algorithm based on N-jettiness that provides an exclusive, fixed-number jet reconstruction method with smooth transition capabilities between resolved and boosted regimes, avoiding split/merge issues.

Contribution

The paper introduces XCone, a new jet algorithm utilizing N-jettiness with a conical geometric measure, enabling fixed-number jet identification and improved handling of overlapping jets.

Findings

XCone effectively reconstructs jets in both resolved and boosted regimes.

The algorithm avoids split/merge criteria used in traditional cone algorithms.

N-jettiness provides a quality measure for jet-like event topology.

Abstract

We introduce a new jet algorithm called XCone, for eXclusive Cone, which is based on minimizing the event shape N-jettiness. Because N-jettiness partitions every event into N jet regions and a beam region, XCone is an exclusive jet algorithm that always returns a fixed number of jets. We use a new "conical geometric" measure for which well-separated jets are bounded by circles of radius R in the rapidity-azimuth plane, while overlapping jet regions automatically form nearest-neighbor "clover jets". This avoids the split/merge criteria needed in inclusive cone algorithms. A key feature of XCone is that it smoothly transitions between the resolved regime where the N signal jets of interest are well separated and the boosted regime where they overlap. The returned value of N-jettiness also provides a quality criterion of how N-jet-like the event looks. We also discuss the N-jettiness factorization theorems that occur for various jet measures, which can be used to compute the associated exclusive N-jet cross sections. In a companion paper, the physics potential of XCone is demonstrated using the examples of dijet resonances, Higgs decays to bottom quarks, and all-hadronic top pairs.