The first calculation of fractional jets
Author(s)
Bertolini, Daniele; Thaler, Jesse; Walsh, Jonathan R.
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In collider physics, jet algorithms are a ubiquitous tool for clustering particles into discrete jet objects. Event shapes offer an alternative way to characterize jets, and one can define a jet multiplicity event shape, which can take on fractional values, using the framework of “jets without jets”. In this paper, we perform the first analytic studies of fractional jet multiplicity Ñ [subscript jet] in the context of e [superscript +] e [superscript −] collisions. We use fixed-order QCD to understand the Ñ [subscript jet] cross section at order α [2 over s], and we introduce a candidate factorization theorem to capture certain higher-order effects. The resulting distributions have a hybrid jet algorithm/event shape behavior which agrees with parton shower Monte Carlo generators. The Ñ [subscript jet] observable does not satisfy ordinary soft-collinear factorization, and the Ñ [subscript jet] cross section exhibits a number of unique features, including the absence of collinear logarithms and the presence of soft logarithms that are purely non-global. Additionally, we find novel divergences connected to the energy sharing between emissions, which are reminiscent of rapidity divergences encountered in other applications. Given these interesting properties of fractional jet multiplicity, we advocate for future measurements and calculations of Ñ [subscript jet] at hadron colliders like the LHC.
Date issued
2015-05Department
Massachusetts Institute of Technology. Center for Theoretical Physics; Massachusetts Institute of Technology. Department of PhysicsJournal
Journal of High Energy Physics
Publisher
Springer-Verlag
Citation
Bertolini, Daniele, Jesse Thaler, and Jonathan R. Walsh. “The First Calculation of Fractional Jets.” J. High Energ. Phys. 2015, no. 5 (May 2015).
Version: Final published version
ISSN
1029-8479
1126-6708