Herwig 7 is hosted by Hepforge, IPPP Durham

Older Herwig++ Versions

Herwig++ 2.6.3 release

2013-02-22: Herwig++ 2.6.3 has been released. It requires ThePEG 1.8.3.

The main improvement in this small bug fix release is a fix for some broken displaced vertices. In some circumstances, internal technical vertices that only changed a particle's momentum caused a displacement to occur. Thanks to ATLAS for the bug report!

Herwig++ 2.6.2 release

2013-02-01: Herwig++ 2.6.2 has been released. It requires ThePEG 1.8.2.

The main improvements are

  • fixes for the PDF and scale choices in POWHEG events, which should solve reported anomalies in POWHEG jet rates, and
  • the possibility of including branching ratio factors in the reported cross-section.

Herwig++ 2.6.1 release

2012-10-16: Herwig++ 2.6.1 has been released. It requires ThePEG 1.8.1.

The main improvements are

  • The width treatment in BSM models has been made more robust and is now switched on by default.
  • Improvements to Matchbox and the Dipole shower.
  • Little Higgs models are now available.
  • Several smaller bugs were fixed. A special thanks to ATLAS for the many useful reports!

Herwig++ 2.6.0 release

2012-05-21: Herwig++ 2.6.0 has been released. It requires ThePEG 1.8.0.

The main improvements are

  • A new NLO framework, "Matchbox", for performing NLO calculations at fixed order or matched to parton showers.
  • A first implementation of the coherent dipole shower algorithm.
  • Alternative samplers and the ExSample library.
  • An interface to events generated with AlpGen, allowing for MLM merging.
  • New BSM models for colour sextets, the CDF t-tbar asymmetry and Z'
  • POWHEG VBF production of Higgs bosons.
  • Automatic extrapolation of the energy-dependent underlying-event parameter pTmin

Herwig++ 2.5.2 release

2011-11-02: Herwig++ 2.5.2 has been released. It requires ThePEG 1.7.2.

If you use LesHoches input with tau spin correlations, you should switch to using ThePEG 1.7.3 instead. Other users don't need to update.

The main improvements are

  • Version 3 of our colour reconnection tunes is now enabled by default. Please note that the pT parameter is energy-dependent and needs to be modified when an LHC run is not at 7 TeV.
  • The jet vetoing model by Schofield and Seymour (arXiv:1103.4811) is available via Evolver:ColourEvolutionMethod, PartnerFinder:PartnerMethod and SplittingFunction:SplittingColourMethod. The default behaviour is unchanged.
  • The initialization process for BSM runs is significantly faster.
  • Decay mode files in the SLHA format can now be read separately in any BSM model with 'set Model:DecayFileName filename'
  • Charged- and neutral-current DIS processes implementing the POWHEG method are now available.

Herwig++ 2.5.1 release

2011-06-24: Herwig++ 2.5.1 has been released. It requires ThePEG 1.7.1.

The main improvements are

  • Version 2 of our colour reconnection tunes is now enabled by default. Version 1 has been withdrawn.
  • Better handling of unusual SLHA points in SUSY models.
  • Restructured setup of weak current decays.

Herwig++ 2.5.0 release

2011-02-08: Herwig++ 2.5.0 has been released. It requires ThePEG 1.7.0.

The main improvements are

  • new next-to-leading order (NLO) matrix elements, including weak boson pair production
  • a colour reconnection model, with first tunes available on our tune pages
  • diffractive processes
  • additional models of BSM physics
  • new leading-order matrix elements for hadron–hadron, lepton–lepton collisions and photon-initiated processes

Additionally, the MC@NLO program can now generate partonic configurations which can be showered and hadronized using Herwig++ to produce events with next-to-leading-order accuracy in the MC@NLO approach to matching.

Herwig++ 2.4.2 release

2009-12-11: Herwig++ 2.4.2 has been released. It requires ThePEG 1.6.1.

The main improvements are

  • Fixes to the numerical stability of tau decays which should address many of the momentum violation problems that have been reported.
  • The longitudinal boost to the QED radiation in hadron collisions is now included correctly.
  • Several improvements to numerical stability of decayers and QED radiation.
  • A speed increase of a few percent for typical runs, from improved handling of decay chain boosts.
  • A fix for the gluino -> gluon neutralino ME.
  • A fix for the misplaced K0 -> K_L/K_S vertex.
  • The example input files for Powheg processes now set the NLO alpha_S correctly.
  • Build fixes for OS X Snow Leopard.

Please read both the 'NEWS' files for the detailed list of changes.

Please respect the MCnet guidelines for Event Generator authors and users.

Contact herwig@projects.hepforge.org with comments or questions.

Herwig++ 2.4.1 release

2009-11-20: Herwig++ 2.4.1 has been released. It requires ThePEG 1.6.0.

The main new features in ThePEG are

  • A reworked helicity amplitude framework, which makes writing model vertices easier.
  • Easier handling of decay mode names in input files: the ordering of decay products is free.
  • ThePEG's repository command language includes a 'help' functionality.

The main new features in Herwig++ are

  • Soft QED radiation in Z decays is fully 1-loop by default.
  • Soft QED radiation is enabled in BSM decays and all perturbative decays by default.
  • Spin correlations are switched on by default for all perturbative decays.
  • The scale choice for Powheg and BSM processes can be chosen in the input files.
  • All file output (except for analyses) can be redirected to stdout.
  • SLHA output for internally calculated SUSY branching ratios.
  • A model for transplanckian scattering.

Many other improvements have been incorporated, please read both the 'NEWS' files for the detailed list of changes. Some of the changes may need small modifications to user code. Please contact us if you have problems!

Please respect the MCnet guidelines for Event Generator authors and users.

Contact herwig@projects.hepforge.org with comments or questions.

Herwig++ 2.4.0 release

2009-09-02:
We have updated the tarball to include the new tuned values for the underlying event.

2009-09-01: Herwig++ 2.4.0 has been released. It requires ThePEG 1.5.0.

The main new features are

  • Several new matrix elements,
  • MRST LO** as the new default PDF set,
  • a retune of shower, hadronization and underlying event parameters,
  • direct support for Rivet and HepMC from within ThePEG instead of Herwig++,
  • implementation of the HepMC status code for generator-specific particles

Herwig++ 2.3.2 release

2009-05-08: Herwig++ 2.3.2 has been released. It requires ThePEG 1.4.2.

In addition to several small fixes, this release contains many improvements for BSM physics, especially the ability to select exclusive production of a final state, and an improved calculation of three-body decay modes at non-standard SUSY points.

More information can be found in the NEWS files.

Please respect the MCnet guidelines for Event Generator authors and users.

Contact herwig@projects.hepforge.org with comments or questions.

Herwig++ 2.3.1 release

2009-03-31: Herwig++ 2.3.1 has been released. It requires ThePEG 1.4.1.

The main changes are a fix for a wrongly applied PDF veto in parton shower qbar->qbar g splittings, inclusion of the Contrib directory contents, clearer error messages for Les Houches file interactions, better floating point stability in edge cases and several smaller fixes in the user interface.

Please respect the MCnet guidelines for Event Generator authors and users.

Contact herwig@projects.hepforge.org with comments or questions.

Herwig++ 2.3.0 release

2008-12-02: Herwig++ 2.3.0 has been released. It requires ThePEG 1.4.0.

The main new features are

  • Lepton-Hadron collisions
  • several processes acuurate at NLO in the POWHEG scheme
  • Three-body decays and finite-width effects for the BSM models
  • New baryon decay models including excited baryon multiplets
  • Addition of a soft component to the multiple scattering model of the underlying event and the option to choose more than one hard scattering explicitly.
  • New matrix elements for DIS and e+e- processes
  • A new 'Contrib' directory, containing external modules that will hopefully be of use to some users, but which are not supported at the same level as the main Herwig++ code.

Please respect the MCnet guidelines for Event Generator authors and users.

Contact herwig@projects.hepforge.org with comments or questions.

Herwig++ 2.2.1 release

2008-07-09: Herwig++ 2.2.1 has been released. It requires ThePEG 1.3.0.

The main change is a new handling of decay modes, which should be transparent to end users. Several memory leaks have been fixed, and a list of tickets addressed. See the NEWS files for details.

Please respect the MCnet guidelines for Event Generator authors and users.

Herwig++ 2.2.0 release

2008-04-18: Herwig++ 2.2.0 has been released. It requires ThePEG 1.2.0.

The major change is in the library structure: Herwig++ now works as a full plugin to the ThePEG framework, and does not need to be linked at compile time anymore. For interface authors, we have a transition help page, listing the few required changes to your code from 2.1 to 2.2.

Please respect the MCnet guidelines for Event Generator authors and users.

Herwig++ 2.1.4 release

2008-03-03: Herwig++ 2.1.4 has been released. It requires ThePEG 1.1.2.

The only change is a workaround for bug 152 (nonsensical vertex positions for unphysical particles) reported by CMS. Until a fix can be impemented, all unphysical particles will have their production vertices set to zero. Vertex displacements for hadrons are unaffected.

Please respect the MCnet guidelines for Event Generator authors and users.

Note for Mac OS X users.

Herwig++ 2.1.3 release

2008-02-25: Herwig++ 2.1.3 has been released. It requires ThePEG 1.1.2.

The main improvements are:

  • A fix for bug 141, a segfault problem with user interfaces.
  • Selection of units for the HepMC output is now possible.
  • Hadronization improvements and retune.

See the NEWS file in the tarball for a full list.

Please respect the MCnet guidelines for Event Generator authors and users.

Note for Mac OS X users.

Herwig++ 2.1.2 release

2008-01-05: Herwig++ 2.1.2 has been released. It has been tested with ThePEG 1.1.1.

The main improvements are:

  • a fix for bug 127 (complete implementation of HepMC file IO) provided by Fred Stober
  • a fix for bug 128 (incorrect values of pi in histogram limits)

See the NEWS file in the tarball for a full list.

Please respect the MCnet guidelines for Event Generator authors and users.

Details of the new features of the 2.1 series can be found in the Herwig++ 2.1 release note.

Installation guide.

Note for Mac OS X users.

Herwig++ 2.1.1 release

2007-12-08: Herwig++ 2.1.1 has been released. It has been tested with the matching new release of ThePEG, 1.1.1.

The main improvements are:

  • fully reproducible events for a given random number seed across all architectures and operating systems (in ThePEG 1.1.1);
  • a fix for bug 123 (nan for some vertex positions) reported by Genser.

See the NEWS file in the tarball for a full list.

Please respect the MCnet guidelines for Event Generator authors and users.

Details of the new features of the 2.1 series can be found in the Herwig++ 2.1 release note.

Installation guide.

Note for Mac OS X users.

Herwig++ 2.1 release

2007-11-20: Herwig++ 2.1.0 has been released. It has been tested with ThePEG 1.1.

Please respect the MCnet guidelines for Event Generator authors and users.

Details of the new features can be found in the Herwig++ 2.1 release note.

Installation guide.

Note for Mac OS X users.

Herwig++ 2.0.3 bugfix release

2007-08-21: Herwig++ 2.0.3 has been released. It has been tested with CLHEP-2.0.2.2 and ThePEG 1.0.1.

Please respect the MCnet guidelines for Event Generator authors and users.

Details of the resolved bugs can be found in the NEWS file.

Installation guide.

Herwig++ 2.0.2 bugfix release

2007-07-06: Herwig++ 2.0.2 has been released. It has been tested with CLHEP-2.0.2.2 and ThePEG 1.0.1.

Please respect the MCnet guidelines for Event Generator authors and users.

Details of the resolved bugs can be found in the NEWS file. The input files are now extensively documented.

Installation guide.

Herwig++ 2.0.1 bugfix release

2006-12-05: The Herwig++ 2.0.1 release has been tested with CLHEP-2.0.2.2 and ThePEG 1.0.1.

Details of the resolved bugs can be found in the NEWS file.

Installation guide.

Herwig++ 2.0

2006-09-28: The Herwig++ 2.0 release has been tested with CLHEP-2.0.2.2 and ThePEG 1.0.

The release note.

Installation guide.

Herwig++ 2.0 beta

This version was intended for integration testing with experimenetal software frameworks. We strongly recommend that against its use now Herwig++ 2.0 has been released. The Herwig++ 2.0 beta release has been tested with CLHEP-2.0.2.2 and ThePEG-2006-01-31.

Update 2006-05-12: A bugfix to correct the azimuthal distribution of initial state radiation is now included.

The release note.

Installation guide.