Herwig is a multi-purpose particle physics event generator. It is built based on the experience gained with both the HERWIG 6 and Herwig++ 2 event generators. Continuing the Herwig++ 2 development, Herwig 7.0 (Herwig++ 3.0) replaces any prior HERWIG or Herwig++ versions.
Herwig provides significantly improved and extended physics capabilities when compared to both its predecessors, HERWIG 6 and Herwig++ 2, while keeping the key model motivations such as coherent parton showers (including angular-ordered and dipole-based evolution), the cluster hadronization model, an eikonal multiple-interaction model, highly flexible BSM capabilities and improved perturbative input using next-to-leading order QCD.
Herwig is based on ThePEG.