GRACE-NLO for the LHC

Automatic Feynman-amplitude calculation system, GRACE , is a generator of event generators, which was originally designed to calculate the processes in the standard electroweak theory. Recently GRACE has been extended to treat next-to-leading order (NLO) QCD calculations ( GRACE-NLO ). Matrix elements of loop diagrams as well as those of tree level ones can be generated using the GRACE system. A soft/collinear singularity is treated using a leading-log subtraction method. Higher order re-summation of the soft/collinear correction by the parton shower method is combined with the NLO matrix-element without any double-counting in this method. For the LHC physics, the GR@PPA framework has been prepared to include the parton distribution function (PDF) and the treatment of lots of subprocesses. Combing GRACE-NLO with the GR@PPA framework, the event generators for W + j e t and di-photon processes are given for demonstrating a validity of this method.

[1]  K. Kato,et al.  GR@PPA 2.7 event generator for pp/pp collisions , 2006, Comput. Phys. Commun..

[2]  S. Frixione,et al.  Matching NLO QCD computations and parton shower simulations , 2002, hep-ph/0204244.

[3]  B. Pötter,et al.  Matching parton showers to the QCD-improved parton model in deep-inelastic eP scattering , 2001 .

[4]  T. Sjöstrand.  High-energy-physics event generation with PYTHIA 5.7 and JETSET 7.4 , 1994 .

[5]  Y. Kurihara,et al.  with a production , 1997 .

[6]  J. Fujimoto,et al.  QCD event generators with next-to-leading order matrix-elements and parton showers , 2002, hep-ph/0212216.

[7]  B. Pötter.  Combining QCD matrix elements at next-to-leading order with parton showers in electroproduction , 2000 .

[8]  Hidekazu Tanaka.  Numerical calculation of helicity amplitudes for processes involving massive fermions , 1990 .

[9]  Yoshimitsu Shimizu,et al.  Numerical calculation of Feynman amplitudes for electroweak theories and an application to e+e−→W+W−γ , 1991 .

[10]  W. Yao,et al.  Review of Particle Physics (2006) , 2006 .

[11]  J. Fujimoto,et al.  Two-body and three-body decays of charginos in one-loop order in the MSSM , 2007 .

[12]  M. Dobbs.  Incorporating next-to-leading order matrix elements for hadronic diboson production in showering event generators , 2001, hep-ph/0103174.

[13]  Y. Kurihara.  Dimensionally regularized one-loop tensor integralswith massless internal particles , 2005 .

[14]  L. Suter,et al.  Herwig++ 2.5 Release Note , 2002, 1102.1672.