Ee4fγ—A program for e+e−→4f,4f γ with nonzero fermion masses

Abstract

A computer program ee4f γ for calculating cross-sections of any four fermion final state of e + e −-annihilation at high energy and the corresponding bremsstrahlung reaction that is possible in the framework of the Standard Model is presented. As the fermion masses are arbitrary, the cross-sections for channels that do not contain e + and/or e − in the final state can be computed without any collinear cut, the on-shell top quark production can be studied and the Higgs boson exchange can be incorporated in a consistent way. The program can be used as a Monte Carlo generator of unweighted events as well. Program summary Title of program: ee4f γ Version: 1.0 (February 2004) Catalogue identifier: ADTQ Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADTQ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: none Computers: all Operating systems: Unix/Linux Programming language used: FORTRAN 90 CPC Program Library subprograms used: RANLUX, ACPR RANLUX 79 (1994) 111—a random number generator Memory required to execute with typical data: 4.0 Mb No. of bits in a word: 32 No. of bytes in distributed program, including test data, etc.: 364 490 No. of lines in distributed program, including test data, etc.: 45 278 Distribution format: tar gzip file Nature of physical problem: Description of all e + e −→4 fermions and corresponding bremsstrahlung reactions that are possible in the Standard Model (SM) to lowest order and with nonzero fermion masses at center of mass energies typical for next generation linear colliders. Such reactions are relevant, typically, for W-pair or intermediate mass Higgs boson production and decay. Method of solution: Matrix elements are calculated with the helicity amplitude method. The phase space integration is performed numerically utilizing a multi-channel Monte Carlo method. Restrictions on complexity of the problem: No higher order effects are taken into account, except for assuming the fine structure constant and the strong coupling at the appropriate scale and partial summation of those one particle irreducible loop corrections which are inducing the (fixed) finite widths of unstable particles. Typical running time: The running time depends strongly on a selected channel and desired precision of the result. The results of the appended test run have been obtained on a 800 MHz Pentium III processor with the use of Absoft FORTRAN 90 compiler in about 9 minutes. In order to obtain a precision level below one per mile a few million calls to the integrand are required. This results in less than one hour running time for the fastest channel e +e −→ν μ ν ̄ μν τ ν ̄ τ and more than 100 hours running time for the slowest channel e + e −→ e + e − e + e −. However, the typical running time for channels that are relevant for the W-pair or Higgs boson production is several hours.