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Matching tree-level matrix elements with interleaved showers

Lönnblad, Leif LU and Prestel, Stefan LU (2012) In Journal of High Energy Physics
Abstract
We present an implementation of the so-called CKKW-L merging scheme for combining multi-jet tree-level matrix elements with parton showers. The implementation uses the transverse-momentum-ordered shower with interleaved multiple interactions as implemented in PYTHIA8. We validate our procedure using e(+)e(-)-annihilation into jets and vector boson production in hadronic collisions, with special attention to details in the algorithm which are formally sub-leading in character, but may have visible effects in some observables. We find substantial merging scale dependencies induced by the enforced rapidity ordering in the default PYTHIA8 shower. If this rapidity ordering is removed the merging scale dependence is almost negligible. We then... (More)
We present an implementation of the so-called CKKW-L merging scheme for combining multi-jet tree-level matrix elements with parton showers. The implementation uses the transverse-momentum-ordered shower with interleaved multiple interactions as implemented in PYTHIA8. We validate our procedure using e(+)e(-)-annihilation into jets and vector boson production in hadronic collisions, with special attention to details in the algorithm which are formally sub-leading in character, but may have visible effects in some observables. We find substantial merging scale dependencies induced by the enforced rapidity ordering in the default PYTHIA8 shower. If this rapidity ordering is removed the merging scale dependence is almost negligible. We then also find that the shower does a surprisingly good job of describing the hardness of multi-jet events, as long as the hardest couple of jets are given by the matrix elements. The effects of using interleaved multiple interactions as compared to more simplistic ways of adding underlying-event effects in vector boson production are shown to be negligible except in a few sensitive observables. To illustrate the generality of our implementation, we also give some example results from di-boson production and pure QCD jet production in hadronic collisions. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Jets, Phenomenological Models, Parton Model, QCD
in
Journal of High Energy Physics
issue
3
publisher
Springer
external identifiers
  • wos:000302412100019
  • scopus:84859534346
ISSN
1126-6708
DOI
10.1007/JHEP03(2012)019
language
English
LU publication?
yes
id
926dc31a-6591-4c28-a702-0ee75f7da79e (old id 2562846)
date added to LUP
2012-06-01 12:02:50
date last changed
2017-11-12 03:09:19
@article{926dc31a-6591-4c28-a702-0ee75f7da79e,
  abstract     = {We present an implementation of the so-called CKKW-L merging scheme for combining multi-jet tree-level matrix elements with parton showers. The implementation uses the transverse-momentum-ordered shower with interleaved multiple interactions as implemented in PYTHIA8. We validate our procedure using e(+)e(-)-annihilation into jets and vector boson production in hadronic collisions, with special attention to details in the algorithm which are formally sub-leading in character, but may have visible effects in some observables. We find substantial merging scale dependencies induced by the enforced rapidity ordering in the default PYTHIA8 shower. If this rapidity ordering is removed the merging scale dependence is almost negligible. We then also find that the shower does a surprisingly good job of describing the hardness of multi-jet events, as long as the hardest couple of jets are given by the matrix elements. The effects of using interleaved multiple interactions as compared to more simplistic ways of adding underlying-event effects in vector boson production are shown to be negligible except in a few sensitive observables. To illustrate the generality of our implementation, we also give some example results from di-boson production and pure QCD jet production in hadronic collisions.},
  author       = {Lönnblad, Leif and Prestel, Stefan},
  issn         = {1126-6708},
  keyword      = {Jets,Phenomenological Models,Parton Model,QCD},
  language     = {eng},
  number       = {3},
  publisher    = {Springer},
  series       = {Journal of High Energy Physics},
  title        = {Matching tree-level matrix elements with interleaved showers},
  url          = {http://dx.doi.org/10.1007/JHEP03(2012)019},
  year         = {2012},
}