You are looking at the page for a historic release! With the release of PYTHIA 8.3, there should be no reason for anyone to download and run any version of PYTHIA 8.1. These pages are, however, kept online in the case an old version is needed to reproduce a historic result.


With the release of PYTHIA 8.1, this new C++ version series took over from the older Fortran 77-based PYTHIA 6.4 one as the new standard. It was strongly recommended to move to PYTHIA 8.1 for LHC studies, although for practical reasons the transition was a slow one in the experimental community.

This initial PYTHIA 8.1 release is focussed towards LHC and Tevatron applications, i.e. high-energy p p and pbar p collisions. Also e+ e- and mu+ mu- annihilation processes may be simulated, but not e.g. e p, gamma p or gamma gamma collisions. This is the major exception where PYTHIA 6.4 still has more to offer. For the rest PYTHIA 8.1 offers many features not found in PYTHIA 6.4, which should make a transition worthwhile.

The release of PYTHIA 8.2 in October 2014 means that PYTHIA 8.1 will not be developed any further. Almost complete backwards compatibility is maintained, so the transition to 8.2 should be easy.


To get going with the program, do the following (on a Linux or Mac OS X system):


All necessary information how to run the program is available in subdirectories of the pythia8186 directory you unpacked above, and copies of them are also linked here.

In addition, the complete PYTHIA 6.4 Physics and Manual is still relevant for most of the physics in 8.1. Also the manual parts may be helpful since many 8.1 settings have exact counterparts in 6.4, but finding them may be too time-consuming for the normal user.


Earlier versions

Normally there should be no reason now to install an older, obsolete version.
However, for backwards checks, this might be required, so the previous ones can be found on the downloads page.

Note that version 8.170 is not recommended owing to unfortunate bug

Working materiel

In this section is collected some of the internal documents used in preparing the code.

The updates of branching ratios to the 2012 Review of Particle Physics for