HERWIG Information

HERWIG is a Fortran Monte Carlo package for simulating Hadron Emission Reactions With Interfering Gluons, written by Pino Marchesini, Bryan Webber, Giovanni Abbiendi, Gennaro Corcella, Ian Knowles, Stefano Moretti, Kosuke Odagiri, Peter Richardson, Mike Seymour, and Luca Stanco. It should not be confused with the C++ program Herwig++ (see below).

Version 6.521 was released on the 11th of March 2013. The HERWIG source code can be obtained here.

If you use HERWIG, please refer to it something along the lines of:
HERWIG 6.5, G. Corcella, I.G. Knowles, G. Marchesini, S. Moretti, K. Odagiri, P. Richardson, M.H. Seymour and B.R. Webber, JHEP 0101 (2001) 010 [hep-ph/0011363]; hep-ph/0210213.
Copies of these papers can be obtained here (postscript format): hep-ph/0011363; hep-ph/0210213.
The manual is also available (with some minor corrections) in pdf format.

Furthermore, if you use any supersymmetric processes, please refer also to:
S. Moretti, K. Odagiri, P. Richardson, M.H. Seymour and B.R. Webber, JHEP 0204 (2002) 028 [hep-ph/0204123].
A copy of this paper can be obtained here: hep-ph/0204123.

The classic paper on HERWIG, although by now very out of date, is:
G. Marchesini, B.R. Webber, G. Abbiendi, I.G. Knowles, M.H. Seymour and L. Stanco, Computer Phys. Commun. 67 (1992) 465.
A copy of this paper can be obtained here.

We are always trying to update our mailing list of users. If you want to add or delete your name from the list, please let us know. 


HERWIG has a wiki, hosted by the CEDAR project. Click on New Ticket to report a bug. By filling in your email address where requested, you will receive reports on its progress.

Future plans

Version 6.5 has always been foreseen as the final Fortran version of HERWIG. The recent sub-version releases are tidying up the last few loose ends.

For serious event generation, HERWIG has been replaced by Herwig++, version 2.4 of which is already available, providing a complete simulation of most types of collider events. Herwig++ is built on the framework of ThePEG.

HERWIG will continue to be available and maintained at a low level as long as there is a demand for a Fortran program with its particular features, such as angular-ordered showering, cluster hadronization and SUSY spin correlations.


The main new feature of version 6.505 was an improved interface to the JIMMY generator for multiple interactions. This is a separate package written by Jon Butterworth, Jeff Forshaw, Mike Seymour and Rod Walker. Jimmy is now a plug-and-play add-on: HERWIG can be run with or without it without any modifications. It also runs correctly in 'underlying event' mode for any combination of hadron, photon or electron beam. The code, and further details on how to use it, can be obtained from Jimmy's home page.

The MC@NLO Package

MC@NLO is a package for combining a Monte Carlo event generator with Next-to-Leading-Order calculations of rates for QCD processes and is based on HERWIG. More information can be obtained here.


One of the major advances in 6.1 was the inclusion of supersymmetry in a completely general way. This reads in an input file of low-energy parameters (masses, couplings, decays, etc), which could be written by hand. It is much easier to generate one with the ISAWIG program, which can be downloaded together with ISAJET here


CHARYBDIS2 is a package for simulating mini-black-hole production at hadron colliders in theories with extra dimensions and TeV-scale gravity. More information can be obtained here.

Old HERWIG versions

The last public version of HERWIG was version 6.4, released (text or postscript) on the 21st of January 2002.

The previous version was version 6.3, released on the 9th of July 2001.

Before that was version 6.2, released on the 27th of November 2000.

Before that was version 6.1, released on the 17th of December 1999.

Before that was version 5.9, released on the 22nd of July 1996.

It is interesting to see how the size of the program grew over the years of its active development. 

Experimental Tunes

In the LEP era we tried to maintain a list of the experimental parameter tunings of HERWIG. 

Related programs

Several other programs are based on HERWIG. Generally these are written by third parties and we are not responsible for improving/maintaining/debugging them. We are however in the process of compiling a list of them for users' reference. So far we have:
HERBVI by Mark Gibbs.
QCDINS by Mark Gibbs, Andreas Ringwald and Fridger Schrempp.
POMWIG by Brian Cox and Jeff Forshaw.
Mike Seymour and Bryan Webber