Abstract
We show how the recently proposed XCone jet algorithm smoothly interpolates between resolved and boosted kinematics. When using standard jet algorithms to reconstruct the decays of hadronic resonances like top quarks and Higgs bosons, one typically needs separate analysis strategies to handle the resolved regime of well-separated jets and the boosted regime of fat jets with substructure. XCone, by contrast, is an exclusive cone jet algorithm that always returns a fixed number of jets, so jet regions remain resolved even when (sub)jets are overlapping in the boosted regime. In this paper, we perform three LHC case studies---dijet resonances, Higgs decays to bottom quarks, and all-hadronic top pairs---that demonstrate the physics applications of XCone over a wide kinematic range.
Highlights
MistagZ + jets Mistag for N = 10.5 m ∈[100,150] GeV0 200 300 400 500 600 700 800 900 1000 p (GeV)mass
When using standard jet algorithms to reconstruct the decays of hadronic resonances like top quarks and Higgs bosons, one typically needs separate analysis strategies to handle the resolved regime of well-separated jets and the boosted regime of fat jets with substructure
While it is possible to combine XCone with jet shapes like N -subjettiness [19, 20] for improved performance in the highly boosted limit, we find in preliminary studies that there is no real advantage to using N = 6 over a more traditional fat jet analysis with N = 2
Summary
For our first case study, we compare the performance of XCone to anti-kT in the resolved regime of well-separated jets. As shown in figures 4a and 4b, both anti-kT and XCone give a good reconstruction of the resonance peak, and they largely agree on the mjj value on an event-by-event basis, without much of an asymmetry in the majjnti-kT − mXjjCone distribution. While the overall area distributions are not so dissimilar ( in the β = 2 case), on an eventby-event basis, there is a population of events where the third XCone jet has substantially smaller jet area, indicative of jet overlap This is the flip side of the area distributions for N = 1, where anti-kT jets could grow larger in size by incorporating a neighboring subjet. In the XCone case, that subjet is separately identified as its own jet for N = 3 Despite these differences, the overall jet reconstruction is still rather similar between XCone and anti-kT. It to handle extreme kinematic circumstances where anti-kT reconstruction inevitability leads to jet merging
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