Exposing the dead cone effect with jet substructure techniques

Maltoni, Fabio; Selvaggi, M.; Thaler, Jesse

doi:10.1103/physrevd.94.054015

Cited by 30 publications

(28 citation statements)

References 45 publications

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“…It is this quantum mechanical feature that goes beyond the classic picture of an unambiguous top quark "particle" whose total energy could be determined in the direct mass measurements. Since the parton showers in all state-of-the-art MC generators account for the dead cone effect [51], it appears obvious that the meaning of m MC t should naturally have a linear dependence on the shower cut Q 0 restricting the ultra-collinear radiation -unless there is a mechanism that leads to a power suppressed effect of order Q 2 0 or higher which we may then safely neglect for the case of the top quark. Therefore, to examine the intrinsic field theoretical meaning of the MC top quark mass parameter m MC t it is essential to start with a careful examination of the production of the top quarks and the ultra-collinear gluons.…”

Section: About This Workmentioning

confidence: 99%

On the cutoff dependence of the quark mass parameter in angular ordered parton showers

Hoang

Plätzer

Samitz

2018

J. High Energ. Phys.

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We show that the presence of an infrared cutoff Q 0 in the parton shower (PS) evolution for massive quarks implies that the generator quark mass corresponds to a Q 0 -dependent short-distance mass scheme and is therefore not the pole mass. Our analysis considers an angular ordered parton shower based on the coherent branching formalism for quasi-collinear stable heavy quarks and splitting functions at next-to-leading logarithmic (NLL) order, and it is based on the analysis of the peak of hemisphere jet mass distributions. We show that NLL shower evolution is sufficient to describe the peak jet mass at full next-to-leading order (NLO). We determine the relation of this short-distance mass to the pole mass at NLO. We also show that the shower cut Q 0 affects soft radiation in a universal way for massless and quasi-collinear massive quark production. The basis of our analysis is (i) an analytic solution of the PS evolution based on the coherent branching formalism, (ii) an implementation of the infrared cut Q 0 of the angular ordered shower into factorized analytic calculations in the framework of Soft-Collinear-Effective-Theory (SCET) and (iii) the dependence of the peak of the jet mass distribution on the shower cut. Numerical comparisons to simulations with the Herwig 7 event generator confirm our findings. Our analysis provides an important step towards a full understanding concerning the interpretation of top quark mass measurements based on direct reconstruction. arXiv:1807.06617v2 [hep-ph]

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Section: About This Workmentioning

confidence: 99%

On the cutoff dependence of the quark mass parameter in angular ordered parton showers

Hoang

Plätzer

Samitz

2018

J. High Energ. Phys.

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“…As a final remark we note that our method was tested only against Pythia8 and thus the exact magnitude of the dead-cone related effects and their onset rely on the specific Pythia8 implementation, which is done via matrix element corrections. However, parton shower generators feature the dead cone effect quite universally with better than 10% agreement wit NLO calcuations [3].…”

Section: Iterative Declustering Of Heavy Flavor-tagged Jetsmentioning

confidence: 85%

“…Recently new ideas were proposed to measure the dead cone using Soft Drop grooming techniques and boosted top quarks at the Large Hadron Collider [3].…”

Section: Introductionmentioning

confidence: 99%

Searching for the dead cone effects with iterative declustering of heavy-flavor jets

Cunqueiro

Płoskoń

2019

Phys. Rev. D

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We present a new method to expose the dead cone effect at colliders using iterative declustering techniques. Iterative declustering allows to unwind the jet clustering and to access the subjets or branches at different depths of the jet tree. Our method consists on declustering the heavy flavourtagged jet using Cambridge-Achen algorithm following the branch containing the heavy flavour at each step and registering the kinematics of the complementary untagged prong. The kinematics of the complementary untagged prong fill a Lund map representing the gluon radiation off the heavy flavour quark at each step of the vacuum shower.Using Pythia8 MC, we show that a simple cut on the Lund plane introduced by log(kT ) > 0, suppresses hadronisation effects and the angular separation between the jet prongs becomes very sensitive to flavour effects. A clear suppression for heavy flavour jets relative to inclusive jets in the region of splitting angles delimited by the relation θ < mQ/E is observed, where mQ is the mass of the heavy quark and E is the energy of the radiator or splitting prong.

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“…[12], the kinematics of the two resulting subjets match the famous Altarelli-Parisi 1 → 2 splitting functions for massless QCD [13]. SoftDrop has been used by CMS [14] and STAR [15] in the context of heavy-ion collisions, and a related strategy was proposed to test the dead cone effect for boosted top quarks [16]. Here, we extend the analysis to QCD with heavy-flavor quarks, exploiting the ability to flavor-tag subjets to test the splitting kinematics of Q → Qg and g → QQ.…”

Section: Introductionmentioning

confidence: 99%

Disentangling heavy flavor at colliders

et al. 2017

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We propose two new analysis strategies for studying charm and beauty quarks at colliders. The first strategy is aimed at testing the kinematics of heavy-flavor quarks within an identified jet. Here, we use the SoftDrop jet-declustering algorithm to identify two subjets within a large-radius jet, using subjet flavor tagging to test the heavy-quark splitting functions of QCD. For subjets containing a J=ψ or ϒ, this declustering technique can also help probe the mechanism for quarkonium production. The second strategy is aimed at isolating heavy-flavor production from gluon splitting. Here, we introduce a new FlavorCone algorithm, which smoothly interpolates from well-separated heavy-quark jets to the gluon-splitting regime where jets overlap. Because of its excellent ability to identify charm and beauty hadrons, the LHCb detector is ideally suited to pursue these strategies, though similar measurements should also be possible at ATLAS and CMS. Together, these SoftDrop and FlavorCone studies should clarify a number of aspects of heavyflavor physics at colliders, and provide crucial information needed to improve heavy-flavor modeling in parton-shower generators.

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Exposing the dead cone effect with jet substructure techniques

Cited by 30 publications

References 45 publications

On the cutoff dependence of the quark mass parameter in angular ordered parton showers

On the cutoff dependence of the quark mass parameter in angular ordered parton showers

Searching for the dead cone effects with iterative declustering of heavy-flavor jets

Disentangling heavy flavor at colliders

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