| 1. |
- Andersen, Jeppe R., et al.
(author)
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Les Houches 2017: Physics at TeV Colliders Standard Model Working Group Report
- 2018. - 07977
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Other publication (other academic/artistic)abstract
- This Report summarizes the proceedings of the 2017 Les Houches workshop on Physics at TeV Colliders. Session 1 dealt with (I) new developments relevant for high precision Standard Model calculations, (II) theoretical uncertainties and dataset dependence of parton distribution functions, (III) new developments in jet substructure techniques, (IV) issues in the theoretical description of the production of Standard Model Higgs bosons and how to relate experimental measurements, (V) phenomenological studies essential for comparing LHC data from Run II with theoretical predictions and projections for future measurements, and (VI) new developments in Monte Carlo event generators.
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| 2. |
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| 3. |
- Bellm, Johannes
(author)
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ColoRea: Colour Rearrangement for Dipole Showers
- 2018
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In: 26th International Workshop on Deep Inelastic Scattering and Related Subjects (DIS 2018). - Trieste, Italy : Sissa Medialab.
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Conference paper (other academic/artistic)abstract
- In this talk I presented an algorithm to correct for wrong assignment of colour dipoles in the cascade of dipole showers. It is explained how simple matrix elements can be used to reorder the colour connections for the evolution of the following cascade. I discuss the possibility to modify the splitting kernels to include an improved behaviour. Further a numerical study is presented that indicates the insensitivity of reordering with matrix elements of higher multiplicity.
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| 4. |
- Bellm, Johannes
(author)
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Colour rearrangement for dipole showers
- 2018
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 78:7
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Journal article (peer-reviewed)abstract
- We present an algorithm to rearrange the colour chains of dipole showers in the shower process according to the colour amplitudes of a simple matrix element. We implement the procedure in the dipole shower of Herwig and show comparisons to data.
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| 5. |
- Bellm, Johannes, et al.
(author)
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Herwig 7.2 release note
- 2020
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:5
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Journal article (peer-reviewed)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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| 6. |
- Bellm, Johannes, et al.
(author)
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High dimensional parameter tuning for event generators
- 2020
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:1
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Journal article (peer-reviewed)abstract
- Monte Carlo Event Generators are important tools for the understanding of physics at particle colliders like the LHC. In order to best predict a wide variety of observables, the optimization of parameters in the Event Generators based on precision data is crucial. However, the simultaneous optimization of many parameters is computationally challenging. We present an algorithm that allows to tune Monte Carlo Event Generators for high dimensional parameter spaces. To achieve this we first split the parameter space algorithmically in subspaces and perform a Professor tuning on the subspaces with binwise weights to enhance the influence of relevant observables. We test the algorithm in ideal conditions and in real life examples including tuning of the event generators Herwig 7 and Pythia 8 for LEP observables. Further, we tune parts of the Herwig 7 event generator with the Lund string model.
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| 7. |
- Bellm, Johannes, et al.
(author)
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Improving the description of multiple interactions in Herwig
- 2020
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:5
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Journal article (peer-reviewed)abstract
- The modeling of multiple parton interactions in Monte Carlo event generators is a crucial part not only for the dressing of signal processes but also to describe data with a minimum bias on the event selection. Much work has and will be put into the theoretical framework and the numerical implementation of these models. In this contribution, we document various improvements of the multiple parton interaction model of Herwig 7 (Bellm et al. in Eur Phys J C76(4):196, 2016), that lead to an improved description of minimum bias and underlying event data.
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| 8. |
- Bellm, Johannes, et al.
(author)
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Jet cross sections at the LHC and the quest for higher precision
- 2020
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:2
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Journal article (peer-reviewed)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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| 9. |
- Bellm, Johannes, et al.
(author)
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PISTA: Posterior Ion STAcking
- 2018
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In: ArXiv e-prints.
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Other publication (other academic/artistic)abstract
- We present a program allowing for the construction of a heavy ion Monte Carlo event using a general purpose proton–proton event generator of the users’ choice to deliver sub–collisions. In this heavy ion event, one or more jets can be added, again using a jet calculation of the users’ choice, allowing for more realistic simulation studies of jets in a heavy ion background.
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| 10. |
- Bellm, Johannes, et al.
(author)
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Spacetime colour reconnection in Herwig 7
- 2019
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In: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 79:12
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Journal article (peer-reviewed)abstract
- We present a model for generating spacetime coordinates in the Monte Carlo event generator Herwig 7, and perform colour reconnection by minimizing a boost-invariant distance measure of the system. We compare the model to a series of soft physics observables. We find reasonable agreement with the data, suggesting that pp-collider colour reconnection may be able to be applied in larger systems.
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