Introduction to PYTHIA
PYTHIA is a program for the generation of high-energy physics events,
i.e. for the description of collisions at high energies between
elementary particles such as e+, e-, p and pbar in various combinations.
It contains theory and models for a number of physics aspects, including
hard and soft interactions, parton distributions, initial- and
final-state parton showers, multiparton interactions, fragmentation
and decay. It is largely based on original research, but also borrows
many formulae and other knowledge from the literature.
Development of JETSET, the first member of the "Lund Monte Carlo" family,
was begun by members of the Lund theory group in 1978, and has continued
since then, on and off. A number of people have contributed to this and
other programs based on it. The most extensive of these is PYTHIA. Over
the years, these two programs have more and more come to be maintained in
common. In 1997 they were therefore merged to one, under the PYTHIA label.
Up until some years ago the main version was PYTHIA 6.4.
In 2004 a rewriting from Fortran 77 to C++ was begun, and with
the release of PYTHIA 8.1 in 2007 the new code became the official
main version. In reality the experimental community continued
to rely largely on the 6.4 version for LHC run 1, but by now the
transition to PYTHIA 8 is almost complete. In 2012 the development
of PYTHIA 6.4 was definitely stopped, and it is now reduced to the
status of legacy code. The release of PYTHIA 8.2 in 2014 underlined
the nature of a by-now mature product with a (reasonably) smooth
The current PYTHIA 8.2 release is found
Other programs in the Lund family and beyond
In addition to PYTHIA and JETSET, several other programs have been
written that are closely associated with them, and in particular make
use of the hadronization machinery.
by Leif Lönnblad and collaborators.
- LEPTO, AROMA, MAJOR, POMPYT and LUCIFER by Gunnar Ingelman
and other members of the Uppsala group.
- FRITIOF and LUCIAE were also originally developed in Lund, but are no
longer maintained by members of the Lund group.
(VIrtual Numerical Collider with Interleaved Antennae) is a
versatile dipole-antenna shower program, by Peter Skands and
collaborators. It operates as a plugin to PYTHIA 8.2, replacing the
internal shower routines, but otherwise retains normal PYTHIA
DIRE (DIpole REsummation) is another dipole shower program for
initial and final state radiation, by Stefan Prestel (and with a
sibling in SHERPA). Like VINCIA it operates as a plugin to PYTHIA 8.2,
and in particular can use the merging machinery implemented there.
It was recently (May 2017) extended to include NLO corrections.