Abstract
The PYTHIA program is a standard tool for the generation of high-energy
collisions, comprising a coherent set of physics models for the evolution from
a few-body hard process to a complex multihadronic final state. It contains a
library of hard processes and models for initial- and final-state parton
showers, multiple parton-parton interactions, beam remnants, string
fragmentation and particle decays. It also has a set of utilities and
interfaces to external programs. While previous versions were written in
Fortran, PYTHIA 8 represents a complete rewrite in C++. The current release is
the first main one after this transition, and does not yet in every respect
replace the old code. It does contain some new physics aspects, on the other
hand, that should make it an attractive option especially for LHC physics
studies.
