Release version 2.2.6

Sherpa 2.2.6

Version 2.2.6 is a bugfix release in the Cho Oyu series and we encourage all users to update to this version.

If you spot any problem, please send us an email. If you would like to be informed about newer releases, please subscribe to our announcement mailing list.


The Sherpa package can be downloaded here: SHERPA-MC-2.2.6.tar.gz

In can also be accessed via git using

  • the web interface
  • or git clone -b rel-2-2-6 for a local clone.

A Manual is included in the Manual/ directory of the tarball (or the git-clone). It is available in the HTML and INFO format and provides extensive documentation of all parameters. It can also be found online.


The main reference describing the physics of Sherpa is JHEP02 (2009) 007. Please cite this publication if you have used Sherpa for your studies. Additionally, each run will produce a file called Sherpa_References.tex which contains information about the modules used in this run and the corresponding publications which should be referred. If in doubt, please seek the advice of the Sherpa authors.


You can find a large collection of example setups for using SHERPA in various different colliders/processes in the Examples/ directory of the tarball. They are also described in the manual.


Known issues

  • Note that dijet production with additional jets merged with the CKKW algorithm is broken in the 2.2.x series (#46)
  • Also see our issue tracker


  • Add initial-state p_z and inelasticity selectors for DIS (#80)
  • Improve the reweighting to include the local K=BBar/B factor in MEPS@NLO runs (#73)
  • Improve treatment of the shower reweighting scale cut-off, it is now applied also when reweighting AlphaS and the PDFs in the CKKW clustering sequence (also mentioned in #73)
  • Adapt status=4 convention in the short HepMC output (#79)
  • Compute approximate NLO EW corrections (and subleading orders) as on-the-fly alternative event weights (#41). See Example in Manual for details. Currently only works with a soon-to-be-released version of OpenLoops.
  • Add a filter between the perturbative and the non-perturbative event phase, which can be used to reject events with parton-level cuts (!94)

Bugfixes (runtime issues)

  • Fix NLO and Variable Selector routines (#70, #88)
  • Fix unweighting treatment for the LocalKFactor (and its on-the-fly variations) in negative events (#94)
  • Fix argument validation in GGH_KFactor_Setter::ClusterMassCorrectionFactor
  • Fix core scale setter for DIS when the incoming particles are ordered ep instead of pe and adapt it for ee->xy (where xy is not a quark pair) (!81)
  • Fix strong coupling reweighting in merging runs in cases where nothing was clustered (#66)
  • Fix beam remnants for DIS setups
  • Fix rejection of rare negative-energy configurations in the shower (#44)
  • Fix treatment of negative UserHook weights in HepMC interface (#100)
  • Fix a mapping in the OpenLoops parameter-setting interface (#87)
  • Fix HEFT Higgs production with COMIX (#114)
  • Fix compatibility issues with recent versions of Rivet

Bugfixes (compilation issues)

  • Fix UFO model builder when running on Darwin (macOS)
  • Fix error when compiling with MCFM support
  • Fix compilation on ARM/PowerPC architectures
  • Make environment importing when building scons scripts more bullet-proof
  • Fix compilation of the HZTool interface add-on