Coherent Showers in Decays of Coloured Resonances

Research output: Contribution to journalArticleResearchpeer-review

Abstract

We present a new approach to coherent parton showers in the decays of colored resonances, based on the notion of “resonance-final” (RF) QCD antennae. A full set of mass- and helicity-dependent 2→3 antenna functions are defined, with the additional requirement of positivity over the respective branching phase spaces. Their singularity structure is identical to that of initial-final (IF) antennae in 2→N hard processes (once mass terms associated with the incoming legs are allowed for), but the phase-space factorizations are different. The consequent radiation patterns respect QCD coherence (at leading color) and reduce to Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and eikonal kernels in the respective collinear and soft limits. The main novelty in the phase-space factorization is that branchings in RF antennae impart a collective recoil to the other partons within the same decay system. An explicit implementation of these ideas, based on the Sudakov veto algorithm, is provided in the vincia antenna-shower plug-in to the pythia 8 Monte Carlo event generator. We apply our formalism, matched to next-to-leading order accuracy using powheg, to top quark production at the LHC, and investigate implications for direct measurement of the top quark mass. Finally, we make recommendations for assessing theoretical uncertainties arising from parton showers in this context.
Original languageEnglish
Article number076006
Number of pages24
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Volume100
Issue number7
DOIs
Publication statusPublished - 11 Oct 2019

Cite this

@article{2ff8d33b9c7e49b3a034eb03d45ee41c,
title = "Coherent Showers in Decays of Coloured Resonances",
abstract = "We present a new approach to coherent parton showers in the decays of colored resonances, based on the notion of “resonance-final” (RF) QCD antennae. A full set of mass- and helicity-dependent 2→3 antenna functions are defined, with the additional requirement of positivity over the respective branching phase spaces. Their singularity structure is identical to that of initial-final (IF) antennae in 2→N hard processes (once mass terms associated with the incoming legs are allowed for), but the phase-space factorizations are different. The consequent radiation patterns respect QCD coherence (at leading color) and reduce to Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and eikonal kernels in the respective collinear and soft limits. The main novelty in the phase-space factorization is that branchings in RF antennae impart a collective recoil to the other partons within the same decay system. An explicit implementation of these ideas, based on the Sudakov veto algorithm, is provided in the vincia antenna-shower plug-in to the pythia 8 Monte Carlo event generator. We apply our formalism, matched to next-to-leading order accuracy using powheg, to top quark production at the LHC, and investigate implications for direct measurement of the top quark mass. Finally, we make recommendations for assessing theoretical uncertainties arising from parton showers in this context.",
author = "Brooks, {Helen M.} and Peter Skands",
year = "2019",
month = "10",
day = "11",
doi = "10.1103/PhysRevD.100.076006",
language = "English",
volume = "100",
journal = "Physical Review D",
issn = "2470-0010",
publisher = "American Physical Society",
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Coherent Showers in Decays of Coloured Resonances. / Brooks, Helen M.; Skands, Peter.

In: Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol. 100, No. 7, 076006, 11.10.2019.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Coherent Showers in Decays of Coloured Resonances

AU - Brooks, Helen M.

AU - Skands, Peter

PY - 2019/10/11

Y1 - 2019/10/11

N2 - We present a new approach to coherent parton showers in the decays of colored resonances, based on the notion of “resonance-final” (RF) QCD antennae. A full set of mass- and helicity-dependent 2→3 antenna functions are defined, with the additional requirement of positivity over the respective branching phase spaces. Their singularity structure is identical to that of initial-final (IF) antennae in 2→N hard processes (once mass terms associated with the incoming legs are allowed for), but the phase-space factorizations are different. The consequent radiation patterns respect QCD coherence (at leading color) and reduce to Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and eikonal kernels in the respective collinear and soft limits. The main novelty in the phase-space factorization is that branchings in RF antennae impart a collective recoil to the other partons within the same decay system. An explicit implementation of these ideas, based on the Sudakov veto algorithm, is provided in the vincia antenna-shower plug-in to the pythia 8 Monte Carlo event generator. We apply our formalism, matched to next-to-leading order accuracy using powheg, to top quark production at the LHC, and investigate implications for direct measurement of the top quark mass. Finally, we make recommendations for assessing theoretical uncertainties arising from parton showers in this context.

AB - We present a new approach to coherent parton showers in the decays of colored resonances, based on the notion of “resonance-final” (RF) QCD antennae. A full set of mass- and helicity-dependent 2→3 antenna functions are defined, with the additional requirement of positivity over the respective branching phase spaces. Their singularity structure is identical to that of initial-final (IF) antennae in 2→N hard processes (once mass terms associated with the incoming legs are allowed for), but the phase-space factorizations are different. The consequent radiation patterns respect QCD coherence (at leading color) and reduce to Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and eikonal kernels in the respective collinear and soft limits. The main novelty in the phase-space factorization is that branchings in RF antennae impart a collective recoil to the other partons within the same decay system. An explicit implementation of these ideas, based on the Sudakov veto algorithm, is provided in the vincia antenna-shower plug-in to the pythia 8 Monte Carlo event generator. We apply our formalism, matched to next-to-leading order accuracy using powheg, to top quark production at the LHC, and investigate implications for direct measurement of the top quark mass. Finally, we make recommendations for assessing theoretical uncertainties arising from parton showers in this context.

UR - http://arxiv.org/abs/arXiv:1907.08980

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