Safe use of jet pull
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Springer
Received: November 15, Revised: December 22, Accepted: January 6, Published: January 17,
2019 2019 2020 2020
Andrew Larkoski,a Simone Marzanib and Chang Wub a
Physics Department, Reed College, 3203 Southeast Woodstock Boulevard, Portland, OR 97202, U.S.A. b Dipartimento di Fisica, Universit` a di Genova and INFN, Sezione di Genova, Via Dodecaneso 33, 16146 Genoa, Italy
E-mail: [email protected], [email protected], [email protected] Abstract: Jet pull is an observable designed to probe colour flow between jets. Thus far, a particular projection of the pull vector, the pull angle, has been employed to distinguish colour flow between jets produced by a colour singlet or an octet decay. This is of particular importance in order to separate the decay of a Higgs boson to a pair of bottom quarks from the QCD background. However, the pull angle is not infra-red and collinear (IRC) safe. In this paper we introduce IRC safe projections of the pull vector that exhibit good sensitivity to colour flow, while maintaining calculability. We calculate these distributions to next-toleading logarithmic accuracy, in the context of the hadronic decay of a Higgs boson, and compare these results to Monte Carlo simulations. This study allows us to define an IRC safe version of the pull angle in terms of asymmetry distributions. Furthermore, because of their sensitivity to wide-angle soft radiation, we anticipate that these asymmetries can play an important role in assessing subleading colour correlations and their modelling in general-purpose Monte Carlo parton showers. Keywords: Jets, QCD Phenomenology ArXiv ePrint: 1911.05090
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP01(2020)104
JHEP01(2020)104
Safe use of jet pull
Contents 1 Introduction
1
2 Jet pull
3 5 5 6 9 11
4 Towards phenomenology 4.1 Non-perturbative corrections 4.2 Numerical studies
12 12 14
5 Asymmetries
17
6 Conclusions and outlook
19
1
Introduction
During this long shutdown phase, the experiments of the CERN Large Hadron Collider (LHC) are gearing up for the third run of the accelerator. While the increase in centreof-mass energy will be modest, the path to discovery of new physics, which thus far has proven so elusive, will likely involve careful analyses of large dataset, in order to expose subtle deviations from Standard Model (SM) predictions. Together with the search for beyond the Standard Model (BSM) particles or interactions, careful studies of the Higgs sector will continue to constitute the second, but equally important, leg of the LHC physics program. In particular, pinning down the couplings of the Higgs boson to the fermions may lead to a deeper understanding of the flavour structure of the SM. In this context, both the ATLAS and CMS collaborations have reached the sought-for statistical significance for the decay of the Higgs into bottom quarks [1, 2] in Run II data. Typical events from proton-proton collisions at the LHC are filled with stronglyinteracting particles, the dynamic
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