Abstract

We study the link between parton dynamics in the collinear limit and the logarithmically enhanced terms of the groomed jet mass distribution, for jets groomed with the modified mass-drop tagger (mMDT). While the leading-logarithmic (LL) result is linked to collinear evolution with leading-order splitting kernels, here we derive the NLL structure directly from triple-collinear splitting kernels. The calculation we present is a fixed-order calculation in the triple-collinear limit, independent of resummation ingredients and methods. It therefore constitutes a powerful cross-check of the NLL results previously derived using the SCET formalism and provides much of the insight needed for resummation within the traditional QCD approach.

Highlights

  • The study of the substructure of jets is an established and highly active component of LHC phenomenology

  • These developments mean that theoretical calculations for jet observables with modified mass-drop tagger (mMDT)/SoftDrop grooming can be carried out to high precision and accurate comparisons can be made to LHC data, which is a program that has already been successfully established with several recent theoretical studies, experimental measurements and phenomenology [15,16,17,18,19,20,21,22,23,24,25,26,27,28]

  • Previous NLL results have entirely been within the framework of Soft-Collinear Effective Theory (SCET) and our work represents an approach which provides strong independent confirmation of the main results involved in the NLL resummation [15,19,30,31]

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Summary

Introduction

The study of the substructure of jets is an established and highly active component of LHC phenomenology. We show that the expected leadinglogarithmic terms emerge from our calculations along with recovering the proper argument of the running coupling in the soft limit and the constant K related to the emergence of the CMW or “physical” coupling [42,43,44] Apart from these standard ingredients we derive the collinear NLL terms finding agreement with the SCET results [15,19,24]. Given our derivation directly from the QCD matrix-elements and independent of any previous SCET work, this constitutes a strong completely independent check on the main results involved in the NLL resummation for mMDT jet mass. We compute separately the contributions from gluon emission with a

Observable definition and leading-log resummation
Leading order calculation and expansion of LL result
Leading-order calculation
LL result at order αs2
NLL at O αs2 : the triple-collinear limit
Gluon emission contribution
Emissions in opposite hemispheres
Emissions in the same hemisphere
Virtual corrections and combined result
CF TRn f contribution
Analytic calculation using web variables
Structure of NLL results
Conclusions
Full Text
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