| 1. |
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| 2. |
- Alwall, J., et al.
(författare)
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A standard format for Les Houches Event Files
- 2007
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Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655. ; 176:4, s. 300-304
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Tidskriftsartikel (refereegranskat)abstract
- A standard file format is proposed to store process and event information, primarily output from partoti-level event generators for further use by general-purpose ones. The information content is identical with what was already defined by the Les Houches Accord five years ago, but then in terms of Fortran commonblocks. This information is embedded in a minimal XML-style structure, for clarity and to simplify parsing.
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| 3. |
- Alwall, J., et al.
(författare)
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Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions
- 2008
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 53:3, s. 473-500
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Tidskriftsartikel (refereegranskat)abstract
- We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all cases, there are important differences.
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| 4. |
- Edström, Daniel, 1986-, et al.
(författare)
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Forces on parallel three-phase AC-conductors during a phase to ground fault
- 2019
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of calculating forces on high current solid conductors, as is present in various types of electrical installations e.g. in substations [1]. An example of such an installation with three parallel conductors is shown in Figure 1. The conductor forces are important for the design of the station, in particular for the conductor geometry and mechanical support.
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| 5. |
- Hoeche, Stefan, et al.
(författare)
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Matching Parton Showers and Matrix Elements
- 2005
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Ingår i: CERN Reports. - 0007-8328. - 9290832657 ; CERN-2005-014, s. 288-299
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We compare different procedures for combining fixed-order tree-level matrix element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW scheme and one based on the so-called MLM scheme using different matrix element generators and different parton cascades. We find that although similar results are obtained in all cases, there are important differences.
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| 6. |
- Lavesson, Nils, et al.
(författare)
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Extending CKKW-merging to One-Loop Matrix Elements
- 2008
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Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; 12:070
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Tidskriftsartikel (refereegranskat)abstract
- We extend earlier schemes for merging tree-level matrix elements with parton showers to include also merging with one-loop matrix elements. In this paper we make a first study on how to include one-loop corrections, not only for events with a given jet multiplicity, but simultaneously for several different jet multiplicities. Results are presented for the simplest non-trivial case of hadronic events at LEP as a proof-of-concept.
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| 7. |
- Lavesson, Nils
(författare)
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Merging Parton Showers and Matrix Elements
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis considers models for describing high energy particle collisions. Existing phenomonological models are modified and new implementations made in order to achive a better description of states with several hard jets. To predict final state hadrons, parton showers are used together with pheonomenological hadronization models. These models describe a wide range of observables, but have the shortcomming that they do not describe states with several jets well. Jets are better described using matrix elements, which then needs to be merged with the parton shower description. Paper I extends one of the earlier merging algorithms to hadron collisions. The resulting algorithm is applied to W plus jets production at the Tevatron. Paper II is a comparison of several different algorithms from merging parton shower and matrix elements. The algorithms are compared for a range of observables for W plus jets production at the Tevatron and the LHC. The systematics of each algorithms is also studied. Paper III deals with the more simple case of e+e- to jets, where the theory is better understood. Here the most simple matrix element is used for the merging and results are studied for four different algorithms. Three of the algorithms are shown to have problems not previously discussed in the literature. Paper IV presents an extension to the merging algorithms, that allows for including matrix elements with loops. The algorithm is applied to e+e- with matrix element contributions of up to order alphas^2.
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| 8. |
- Lavesson, Nils, et al.
(författare)
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Merging parton showers and matrix elements -- back to basics
- 2008
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Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; 4:85
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Tidskriftsartikel (refereegranskat)abstract
- We make a thorough comparison between different schemes of merging fixed-order tree-level matrix element generators with parton-shower models. We use the most basic benchmark of the O(alpha_S) correction to e+e- -> jets, where the simple kinematics allows us to study in detail the transition between the matrix-element and parton-shower regions. We find that the CKKW-based schemes give a reasonably smooth transition between these regions, although problems may occur if the parton shower used is not ordered in transverse momentum. However, the so-called Pseudo-Shower and MLM schemes turn out to have potentially serious problems due to different scale definitions in different regions of phase space, and due to sensitivity to the details in the initial conditions of the parton shower programs used.
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| 9. |
- Lavesson, Nils, et al.
(författare)
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Modeling of streamers in transformer oil using OpenFOAM
- 2014
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Ingår i: Compel. - : Emerald Group Publishing Limited. - 0332-1649. ; 33:4, s. 1272-1281
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Tidskriftsartikel (refereegranskat)abstract
- Purpose – A model for streamers based on charge transport has been developed by MIT and ABB. The purpose of this paper is to investigate the consequences of changing numerical method from the finite element method (FEM) to the finite volume method (FVM) for simulations using the streamer model. The new solver is also used to extend the simulations to 3D. Design/methodology/approach – The equations from the MIT-ABB streamer model are implemented in OpenFOAM which uses the FVM. Checks of the results are performed including verification of convergence. The solver is then applied to some of the key simulations from the FEM model and results presented. Findings – The results for second mode streamers are confirmed, whereas the results for third mode streamers differ significantly leading to questioning of one hypothesis proposed based on the FEM results. The 3D simulations give consistent results and show a way forward for future simulations. Originality/value – The FVM has not been applied to the model before and led to more confidence in second mode result and revising of third mode results. In addition the new simulation method makes it possible to extend the results to 3D.
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| 10. |
- Lavesson, Nils, et al.
(författare)
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W+jets matrix elements and the dipole cascade
- 2005
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Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; 7:54
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Tidskriftsartikel (refereegranskat)abstract
- We extend the algorithm for matching fixed-order tree-level matrix element generators with the Dipole Cascade Model in Ariadne to apply to processes with incoming hadrons. We test the algoritm on for the process W+n jets at the Tevatron, and find that the results are fairly insensitive to the cutoff used to regularize the soft and collinear divergencies in the tree-level matrix elements. We also investigate a few observables to check the sensitivity to the matrix element correction.
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