Factorization Algorithm for Parton Showers beyond the Leading Logarithmic Order of QCD

The GR@PPA event generator has been updated to version 2.7. This distribution provides event generators for V (W or Z) + jets (≤ 4 jets), V V + jets (≤ 2 jets) and QCD multi-jet (≤ 4 jets) production processes at pp and pp collisions, in addition to the four bottom quark productions implemented in our previous work (GR@PPA 4b). Also included are the top-pair and top-pair + jet production processes, where the correlation between the decay products are fully reproduced at the tree level. Namely, processes up to seven-body productions can be simulated, based on ordinary Feynman diagram calculations at the tree level. In this version, the GR@PPA framework and the process dependent matrix-element routines are separately provided. This makes it easier to add further new processes, and allows users to make a choice of processes to implement. This version also has several new features to handle complicated multi-body production processes. A systematic way to combine many subprocesses to a single base-subprocess has been introduced, and a new method has been adopted to calculate the color factors of complicated QCD processes. They speed up the calculation significantly.

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“…The parton shower algorithm, e.g. the NLL parton shower [12], will also be possible to implement by modifying the framework.…”

Section: Introductionmentioning

confidence: 99%

GR@PPA 2.7 event generator for collisions

Tsuno

Kaneko

Kurihara

et al. 2006

Computer Physics Communications

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“…By including the NLL order contributions, ambiguities due to the choice of the factorization scale become sufficiently small compared with the case at the LL order of QCD. An analytic calculation of the transverse momentum distrib- * ) The parton evolutions start from the distribution function at M 0 , which is approximately given by 10) f…”

Section: The Nll Order Contributionsmentioning

confidence: 99%

NLL Order Contributions for Exclusive Processes in Jet-Calculus Scheme

Tanaka¹

2011

Progress of Theoretical Physics

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We investigate the next-to-leading logarithmic (NLL) order contributions of the quantum chromodynamics (QCD) for exclusive processes evaluated by Monte Carlo methods. Ambiguities of the Monte Carlo calculation based on the leading-logarithmic (LL) order approximations are pointed out. To remove these ambiguities, we take into account the NLL order terms. In a model presented in this paper, interference contributions due to the NLL order terms are included for the generation of the transverse momenta in initial-state parton radiations. Furthermore, a kinematical constraint due to parton radiation, which is also a part of the NLL order contributions, is taken into account. This method guarantees a proper phase space boundary for hard scattering cross sections as well as parton radiations. As an example, cross sections for lepton pair productions mediated by a virtual photon in hadron-hadron collisions are calculated, using the jet-calculus scheme for flavor nonsinglet quarks.Comment: 17 pages, 3 figure

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“…Recently, the parton shower model based on the evolution of momentum distributions was extended to the NLL order of QCD with the modified minimal subtraction (MS) scheme 1)7) as well as that with the jet calculus scheme. 8) In a previous paper, 9) we studied factorization schemes for the hard scattering cross sections in hadron-hadron collisions, in which the collinear singularities are subtracted using the MS scheme. In the conventional MS scheme, it has been pointed out that matching between the hard scattering cross section and the initial-state radiation is broken in the calculation of exclusive processes.…”

Section: §1 Introductionmentioning

confidence: 99%

“…In this paper, we examine the JC scheme, 8) in which the coefficient of the subtraction term is given by P [JC] qq (z q , ǫ) = P [JC] qq (z q , ǫ)…”

Section: §1 Introductionmentioning

confidence: 99%

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Drell-Yan Cross Section in the Jet Calculus Scheme

Tanaka¹,

Kobayashi²

2009

Progress of Theoretical Physics

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We calculate factorized cross sections for lepton pair production mediated by a virtual photon in hadron-hadron collisions using the jet calculus scheme, in which a kinematical constraint due to parton radiation is taken into account. This method guarantees a proper phase space boundary for subtraction terms. Some properties of the calculated cross sections are examined. We also discuss matching between the hard scattering cross sections and parton showers at the next-to-leading logarithmic (NLL) order of quantum chromodynamics (QCD).Comment: 18 pages, PTPTeX.sty, 3 Postscript figure

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Factorization Algorithm for Parton Showers beyond the Leading Logarithmic Order of QCD

Cited by 6 publications

References 4 publications

GR@PPA 2.7 event generator for collisions

GR@PPA 2.7 event generator for collisions

NLL Order Contributions for Exclusive Processes in Jet-Calculus Scheme

Drell-Yan Cross Section in the Jet Calculus Scheme

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