| 1. |
- Alcock-Zeilinger, Judith, et al.
(författare)
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Wigner 6 j symbols for SU(N) : Symbols with at least two quark-lines
- 2023
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Ingår i: Journal of Mathematical Physics. - : AIP Publishing. - 0022-2488 .- 1089-7658. ; 64:2
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Tidskriftsartikel (refereegranskat)abstract
- We study a class of SU(N) Wigner 6j symbols involving two fundamental representations and derive explicit formulas for all 6j symbols in this class. Our formulas express the 6j symbols in terms of the dimensions of the involved representations, and they are thereby functions of N. We view these explicit formulas as a first step toward efficiently decomposing SU(N) color structures in terms of group invariants.
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| 2. |
- Bellm, Johannes, et al.
(författare)
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Herwig 7.2 release note
- 2020
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:5
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Tidskriftsartikel (refereegranskat)abstract
- A new release of the Monte Carlo event generator Herwig (version 7.2) is now available. This version introduces a number of improvements over the major version 7.0, notably: multi-jet merging with the dipole shower at LO and NLO QCD; spin correlations in both the dipole and angular-ordered parton showers; an improved choice of evolution variable in the angular-ordered parton shower; improvements to mass effects and top decays in the dipole shower, improvements to the simulation of multiple-parton interactions, including diffractive processes; a new model for baryonic colour reconnection; improvements to strangeness production; as well as a new tune of the hadronisation parameters and support for generic Lorentz structures in BSM models. This article illustrates new features of versions 7.1 and 7.2.
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| 3. |
- Bellm, Johannes, et al.
(författare)
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Jet cross sections at the LHC and the quest for higher precision
- 2020
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:2
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Tidskriftsartikel (refereegranskat)abstract
- We perform a phenomenological study of Z plus jet, Higgs plus jet and di-jet production at the Large Hadron Collider. We investigate in particular the dependence of the leading jet cross section on the jet radius as a function of the jet transverse momentum. Theoretical predictions are obtained using perturbative QCD calculations at the next-to and next-to-next-to-leading order, using a range of renormalization and factorization scales. The fixed order predictions are compared to results obtained from matching next-to-leading order calculations to parton showers. A study of the scale dependence as a function of the jet radius is used to provide a better estimate of the scale uncertainty for small jet sizes. The non-perturbative corrections as a function of jet radius are estimated from different generators.
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| 4. |
- Bittrich, Carsten, et al.
(författare)
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Soft QCD effects in VBS/VBF topologies
- 2022
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 82:9
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Tidskriftsartikel (refereegranskat)abstract
- We consider the impact of multi-parton interactions and colour reconnection on the modeling of vector boson fusion and vector boson scattering (VBS) final states at the Large Hadron Collider (LHC). We investigate how the variation of the model parameters, compatible with a reasonable spread of predictions around typical tuning observables, extrapolates into the VBS phase space. We study the implications of this variation on the total uncertainty budget attached to realistic simulations of the final states in current event generator predictions. We find that the variations have a non-trivial phase space dependence and become comparable in size to the perturbative uncertainties once next-to-leading order predictions are combined with parton shower evolution.
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| 5. |
- Bothmann, Enrico, et al.
(författare)
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A standard convention for particle-level Monte Carlo event-variation weights
- 2023
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Ingår i: SciPost Physics Core. - 2666-9366. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Streams of event weights in particle-level Monte Carlo event generators are a convenient and immensely CPU-efficient approach to express systematic uncertainties in phenomenology calculations, providing systematic variations on the nominal prediction within a single event sample. But the lack of a common standard for labelling these variation streams across different tools has proven to be a major limitation for event-processing tools and analysers alike. Here we propose a well-defined, extensible community standard for the naming, ordering, and interpretation of weight streams that will serve as the basis for semantically correct parsing and combination of such variations in both theoretical and experimental studies.
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| 6. |
- Keppeler, Stefan, et al.
(författare)
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Wigner 6j symbols with gluon lines : completing the set of 6j symbols required for color decomposition
- 2024
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2024:5
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Tidskriftsartikel (refereegranskat)abstract
- We construct a set of Wigner 6j symbols with gluon lines (adjoint representations) in closed form, expressed in terms of similar 6j symbols with quark lines (fundamental representations). Together with these Wigner 6j symbols with quark lines, this gives a set of 6j symbols sufficient for treating QCD color structure for any number of external particles, in or beyond perturbation theory. This facilitates a complete treatment of QCD color structure in terms of orthogonal multiplet bases, without the need of ever explicitly constructing the corresponding bases. We thereby open up for a completely representation theory based treatment of SU(N) color structure, with the potential of significantly speeding up the color structure treatment.
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| 7. |
- Lifson, Andrew, et al.
(författare)
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One-loop calculations in the chirality-flow formalism
- 2023
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In a few recent papers we introduced the chirality-flow formalism, which was shown to make calculations of tree-level Feynman diagrams simple and transparent. Chirality flow, which is based on the spinor-helicity formalism, allows to often immediately analytically write down a tree-level Feynman diagram in terms of spinor inner products. In this paper, we argue that there is also a significant simplification of the Lorentz structure at the one-loop level, at least when using the four-dimensional formulation of the four-dimensional helicity scheme. Additionally, we find that the possible terms in a tensor decomposition of loop integrals are highly constrained, and therefore the tensor reduction procedure is simplified.
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| 8. |
- Olsson, Jimmy, et al.
(författare)
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Resampling algorithms for high energy physics simulations
- 2020
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Ingår i: European Physical Journal C. - : Springer Science and Business Media Deutschland GmbH. - 1434-6044 .- 1434-6052. ; 80:10
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that the method of interleaved resampling in the context of parton showers can tremendously improve the statistical convergence of weighted parton shower evolution algorithms. We illustrate this by several examples showing significant statistical improvement.
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| 9. |
- Valassi, Andrea, et al.
(författare)
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Challenges in Monte Carlo Event Generator Software for High-Luminosity LHC
- 2021
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Ingår i: Computing and Software for Big Science. - : Springer Science and Business Media LLC. - 2510-2044 .- 2510-2036. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- We review the main software and computing challenges for the Monte Carlo physics event generators used by the LHC experiments, in view of the High-Luminosity LHC (HL-LHC) physics programme. This paper has been prepared by the HEP Software Foundation (HSF) Physics Event Generator Working Group as an input to the LHCC review of HL-LHC computing, which has started in May 2020.
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