Journal of High Energy Physics

, 2018:64 | Cite as

The Lund jet plane

  • Frédéric A. Dreyer
  • Gavin P. Salam
  • Grégory SoyezEmail author
Open Access
Regular Article - Theoretical Physics


Lund diagrams, a theoretical representation of the phase space within jets, have long been used in discussing parton showers and resummations. We point out that they can be created for individual jets through repeated Cambridge/Aachen declustering, providing a powerful visual representation of the radiation within any given jet. Concentrating here on the primary Lund plane, we outline some of its analytical properties, highlight its scope for constraining Monte Carlo simulations and comment on its relation with existing observables such as the zg variable and the iterated soft-drop multiplicity. We then examine its use for boosted electroweak boson tagging at high momenta. It provides good performance when used as an input to machine learning. Much of this performance can be reproduced also within a transparent log-likelihood method, whose underlying assumption is that different regions of the primary Lund plane are largely decorrelated. This suggests a potential for unique insight and experimental validation of the features being used by machine-learning approaches.


Jets QCD Phenomenology 


Open Access

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Copyright information

© The Author(s) 2018

Authors and Affiliations

  • Frédéric A. Dreyer
    • 1
    • 2
  • Gavin P. Salam
    • 3
    • 2
    • 4
  • Grégory Soyez
    • 5
    Email author
  1. 1.Center for Theoretical Physics, Massachusetts Institute of TechnologyCambridgeU.S.A.
  2. 2.Rudolf Peierls Centre for Theoretical Physics, Clarendon LaboratoryOxfordU.K.
  3. 3.CERN, Theoretical Physics DepartmentGeneva 23Switzerland
  4. 4.All Souls CollegeOxfordU.K.
  5. 5.IPhT, Université Paris-Saclay, CNRS UMR 3681, CEA SaclayGif-sur-YvetteFrance

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