PROGRAM SUMMARY
Title of program:
YFSWW3, version 1.16
Catalogue identifier:
ADOU
Ref. in CPC:
140(2001)432
Distribution format: tar gzip file
Operating system: UNIX/Linux
High speed store required:
10MK words
Number of lines in distributed program, including test data, etc:
79408
Keywords:
Standard Model (SM), LEP2, Linear colliders (LC), Quantum
electrodynamics (QED), Quantum chromodynamics (QCD), Boson W,
W-pair production, W decay, W branching ratio (BR),
Triple guage boson couplings (TGC), Quartic guage boson
couplings (QGC), Four-fermion (4f) background,
Radiative corrections, Yennie-Frautschi-Suura
(YFS) exponentiation, Initial-state radiation (ISR),
Leading-log (LL) approximation, Coulomb effect,
Final-state radiation (FSR), Electroweak (EW) corrections,
Leading-pole approximation (LPA), Monte Carlo (MC)
simulation/generation, Elementary particle physics,
Event simulation.
Programming language used: Fortran
Computer:
PC Intel Pentium III .
Nature of physical problem:
The process of the W-pair production is important for precise tests of
the Standard Model as well as searches for "new physics" at LEP2 and
future linear colliders. In order to match the experimental precision
necessary for a successful physics programme, quantum effects (the
so-called radiative corrections) have to be included into a theoretical
description of this process. It turns out that not only the so-called
universal corrections (initial-state radiation, the Coulomb effect,
"naive" QCD corrections, etc.) are necessary, but also the O(alpha)
electroweak corrections in the WW production are needed to reach the
desired theoretical accuracy. All these effects should, preferably, be
included in a Monte Carlo event generator in order to account for
realistic experimental set-ups.
Method of solution:
The Monte Carlo event generator for the combined W-pair production and
decay process including O(alpha**3) LL ISR effects, the Coulomb
correction (usual or screened), the "naive" QCD effect, the O(alpha) EW
corrections in the WW production stage, implemented within the YFS
exclusive exponentiation framework is provided. Multiphoton radiation
in the WW production is generated according to the YFS MC method. The
photon radiation in the W decays, normalized to the W BRs, is generated
by the LL-type MC program PHOTOS (up to two photons). The decays of
tau's including radiative corrections are simulated by the dedicated
package TAUOLA. The quark fragmentation/hadronization is performed with
the help of the Lund program JETSET. The program can provide both
weighted and unweighted (weight = 1) events. Any experimental cut and
apparatus efficiency may be introduced easily by rejecting some of the
generated events.
Restrictions:
The LPA is used (in two versions) to describe the signal WW production
process. Multiphoton radiation according to the YFS exponentiation
scheme is generated only for the WW production stage. O(alpha) EW
corrections (in LPA) are included only in the WW production stage. The
ISR effects beyond O(alpha) are included in the LL approximation.
Non-factorizable corrections (interferences between the production and
decay stages) are approximated by the so-called screened Coulomb ansatz.
Spin correlations between the WW production and decays are fully
included only at the Born and the ISR levels. Radiative corrections in
the W decays are included into an overall normalization through the W
BRs, and the real photon radiation is generated in the LL approximation
(up to two photons) by the program PHOTOS. Anomalous triple gauge boson
couplings are included in the Born-like matrix element, i.e. with the
universal SM corrections only. Quartic gauge boson couplings are
implemented according to the Standard Model only (no anomalous
couplings). The tau decays and quark hadronization are performed,
respectively, with the help of the dedicated packages TAUOLA and JETSET.
No 4f background processes are included.
Typical running time:
200 CPU seconds of a PC Intel Pentium III @ 550 MHz per 1000 unweighted
events, for the parameter settings as they are given in the
demonstration program.