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Manuscript Title: PHANTOM: a Monte Carlo event generator for six parton final states at high energy colliders.
Authors: Alessandro Ballestrero, Aissa Belhouari, Giuseppe Bevilacqua, Vladimir Kashkan, Ezio Maina
Program title: PHANTOM (V. 1.0)
Catalogue identifier: AECE_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 180(2009)401
Programming language: Fortran 77.
Computer: Any with a UNIX, LINUX compatible Fortran compiler.
Operating system: UNIX, LINUX.
RAM: 500MB
Keywords: Six fermions, Electroweak symmetry breaking, Higgs, Top, LHC, linear collider.
PACS: 12.15.-y, 11.15.Ex.
Classification: 11.1.

External routines: LHAPDF (Les Houches Accord PDF Interface, http://projects.hepforge.org/lhapdf/), CIRCE (beamstrahlung for e+e- ILC collider).

Nature of problem:
Six fermion final state processes have become important with the increase of collider energies and are essential for the study of top, higgs and electroweak symmetry breaking physics at high energy colliders. Since thousands of Feynman diagrams contribute in a single process and events corresponding to hundreds of different final states need to be generated, a fast and stable calculation is needed.

Solution method:
PHANTOM is a tree level Monte Carlo for six parton final states at proton-proton, proton-antiproton and electron-positron collider. It computes all amplitudes at O(α6EM) and O(α4EMα2s) including possible interferences between the two sets of diagrams. The matrix elements are computed with the helicity formalism implemented in the program PHACT [1]. The integration makes use of an iterative-adaptive multichannel method which, relying on adaptivity, allows use of only a few channels per process. Unweighted event generation can be performed for any set of processes and it is interfaced to parton shower and hadronization packages via the latest Les Houches Accord protocol.

All Feynman diagrams are computed al LO.

Unusual features:
Phantom is written in Fortran 77 but it makes use of structures. The g77 compiler cannot compile it as it does not recognize the structures. The vIntel, Portland Group, True64 HP fortran77 or fortran90 compilers have been tested and can be used.

Running time:
A few hours for a cross section integration of one process at per mille accuracy. One hour for one thousand unweighted events.

[1] A. Ballestrero and E. Maina, Phys. Lett. B350 (1995) 225, (hep-ph/9403244). A. Ballestrero, PHACT 1.0, Program for Helicity Amplitudes Calculations with Tau matrices (hep-ph/9911318) in Proceedings of the 14th International Workshop on High Energy Physics and Quantum Field Theory (QFTHEP 99) , B.B. Levchenko and V.I. Savrin eds. (SINP MSU Moscow), pg. 303.