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[Licence| Download | New Version Template] adct_v2_0.tar.gz(3573 Kbytes)
Manuscript Title: Monte Carlo program KoralW 1.42 for all four-fermion final states in e+e- collisions.
Authors: S. Jadach, W. Placzek, M. Skrzypek, B.F.L. Ward, Z. Was
Program title: KoralW, version 1.42
Catalogue identifier: ADCT_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 119(1999)272
Programming language: Fortran.
Computer: IBM PowerPC M43P240.
Operating system: UNIX (AIX 4.x/HP-UX 10.x), Linux.
RAM: 10M words
Keywords: Particle physics, Elementary, Event simulation, Radiative corrections, Initial State radiation (isr), Leading-logarithms (ll), Approximation, Heavy boson w, 4-fermion processes, Monte carlo (mc), Simulation/generation, Electrodynamics quantum, Chromodynamics quantum, Yennie-frautschi-suura (YFS) exponentiation, Standard model (sm), Lep2.
Classification: 11.2.

Nature of problem:
The W-pair production and decay is and will be used as an important data point for precise tests of the standard electroweak theory at LEP2 and higher energies. The effects due to background processes, QED bremsstrahlung and apparatus efficiency have to be subtracted from the data. The program deals with all e+e- processes leading to 4-fermion final states accompanied with multiphoton initial-state radiation. It also includes the effects of the Coulomb correction, 'naive' QCD, anomalous couplings, quarks hadronization, tau decays and photon radiation in leptonic decays.

Solution method:
The Monte Carlo methods are used to simulate all 4-fermion final-state processes in the e+e- collisions in the presence of multiphoton initial- state radiation. The latter is described in the framework of the YFS exclusive exponentiation. The W-pair production is included in a 'natural' way as a subset of the Feynman diagrams for the above processes, but it can also be generated exclusively by switching to the so-called CC03 process. The Monte Carlo generation is done on an event- by-event basis, with constant or variable weights, where an event is represented by flavours and four-momenta of all respective particles - supplemented with a collection of weights, if the variable weight option is chosen. After the event generation is completed the program provides the cross sections together with their statistical errors for all the processes involved. Any experimental cuts and apparatus efficiencies may be introduced easily by rejecting some of the generated events.

Only processes with 4-fermion final states are considered. QED radiative corrections are implemented in terms of multiphoton ISR in the YFS Monte Carlo framework with the O(alpha**3) LL-type matrix element. For the CC03 subset of diagrams the Coulomb correction for the intermediate WW states is also included. The final-state QED radiation is generated for charged leptons with the help of the program PHOTOS in the LL approximation (up to two photons). QCD effects are included in the so-called "naive QCD" approximation. A part of electroweak corrections is incorporated in the "improved Born approximation" (through appropriate renormalization scheme). Anomalous triple gauge boson couplings are implemented only in the CC03 subset of diagrams (i.e. the W-pair production). Quadruple gauge boson couplings are not implemented. The tau-decays and quark hadronization are performed, respectively, with the help of the dedicated packages TAUOLA and JETSET.

Running time:
On IBM PowerPC M43P240 (266 MHz, 65 CERN units) installation one needs: (a) 2.5 sec per 1000 constant-weight events and 0.6 sec per 1000 variable-weight events for CC03 matrix element and (b) 12500 sec per 1000 constant-weight events and 6 sec per 1000 variable-weight events for a complete 4-fermion matrix element (GRACE). These results are for a default/recommended setting of input parameters but with all decay libraries switched OFF.