| 1. |
- Corke, Richard, et al.
(författare)
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Interleaved parton showers and tuning prospects
- 2011
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :3
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Tidskriftsartikel (refereegranskat)abstract
- General-purpose Monte Carlo event generators have become important tools in particle physics, allowing the simulation of exclusive hadronic final states. In this article we examine the PYTHIA 8 generator, in particular focusing on its parton-shower algorithms. Some relevant new additions to the code are introduced, that should allow for a better description of data. We also implement and compare with 2 -> 3 real-emission QCD matrix elements, to check how well the shower algorithm fills the phase space away from the soft and collinear regions. A tuning of the generator to Tevatron data is performed for two PDF sets and the impact of first new LHC data is examined.
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| 2. |
- Corke, Richard
(författare)
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Multiparton Interaction Models and Parton Shower Studies
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis involves phenomenological models for describing high energy particle collisions. One class of these models, multiparton interactions (MPI), deals with the fact that when colliding two hadrons, it is possible for more than one pair of their constituents to interact. The other deals with parton showers, which are used to fill enhanced regions of phase space and give fully exclusive final states. These two components, when part of an event generation framework, help in the simulation of complete high energy collision events. Paper I presents a study of an extension to the MPI model, enhanced screening, where the amount of colour screening in an incoming hadron is increased in those events with a large amount of activity. Paper II presents another extension to the MPI model, rescattering. Commonly, in MPI models, interactions are between pairs of partons which originate from the incoming hadrons. With rescattering, an MPI can instead involve partons which come from previous interactions or shower branchings. Paper III studies the first emission of the parton shower. First, the interface to a next-to-leading generator, POWHEG-hvq, is examined. Second, a dampening of the first shower emission, based on general matrix element arguments is studied. Paper IV again deals with parton showers. Minor changes to the framework are outlined, before a kinematic comparison of the shower is made against 2 to 3 QCD real emission matrix elements. Finally, tunes of the generator are made to both Tevatron and LHC data. Paper V examines an extension to the impact parameter formalism of the MPI model, where the size of an incoming proton is varied depending on the x value of a parton being taken from it.
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| 3. |
- Corke, Richard, et al.
(författare)
-
Multiparton interactions with an x-dependent proton size
- 2011
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; :5
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical arguments, supported by other indirect evidence, suggest that the wave function of high-x partons should be narrower than that of low-x ones. In this article, we present a modification to the variable impact parameter framework of PYTHIA 8 to model this effect. In particular, a Gaussian hadronic matter profile is introduced, with a width dependent on the x value of the constituent being probed. Results are compared against the default single-and double-Gaussian profiles, as well as an intermediate overlap function.
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| 4. |
- Gustafson, Gösta, et al.
(författare)
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Multi-Parton Interactions at the LHC
- 2011
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We review the recent progress in the theoretical description and experimental observation of multiple parton interactions. Subjects covered include experimental measurements of minimum bias interactions and of the underlying event, models of soft physics implemented in Monte Carlo generators, developments in the theoretical description of multiple parton interactions and phenomenological studies of double parton scattering. This article stems from contributions presented at the Helmholtz Alliance workshop on ”Multi-Parton Interactions at the LHC”, DESY Hamburg, 13-15 September 2010.
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