Sherpa 1.2.3

Version 1.2.3 is an update of Sherpa which contains bugfixes and new features. Please see the Changelog below for a summary of updates.

Download

The Sherpa package can be downloaded here:

• ​SHERPA-MC-1.2.3.tar.gz

A Manual is included in the Manual/ directory of the tarball. It is available in the HTML or INFO format and provides extensive documentation of all parameters. It can also be found online at ​http://projects.hepforge.org/sherpa/doc/SHERPA-MC-1.2.3.html.

A publication describing the physics of the SHERPA Monte-Carlo can be found in ​JHEP02 (2009) 007. This is meant to be the standard reference, please cite this publication if you have used SHERPA for your studies. Additionally each run will create a file called Sherpa_References.tex which contains information about the modules used in this run and the corresponding publications which should be referred.

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 briefly described in the manual.

We also provide a public ​gallery of results obtained with this version of Sherpa. There you can find comparisons to experimental data and to the previous version of Sherpa, as well as studies of systematics especially with respect to ME+PS merging.

A Changelog for important differences between the previous version and this version is provided below.

If you would like to be kept up-to-date about new versions or important updates of Sherpa, please subscribe to our ​announcement mailing list.

Patches/known problems/known bugs/FAQs

All known problems/questions and their solutions can be found on our ​issue tracker (please log in using the given details). If you encounter any problem while installing or running Sherpa, please open a new issue in the tracker.

• Bugfix for automatic alpha_s setting, listed under ​ticket 124. Fix: Apply ​patch file via patch -p0 < model_init_1.patch in the top level directory of your Sherpa installation, and recompile using 'make install'.
• Bugfixes for NLO event generation, not currently listed on the bug tracker. Fix: Apply ​patch file via patch -p0 < nlo_simulation_1.patch in the top level directory of your Sherpa installation, and recompile using 'make install'.
• Bugfix for the Zprime Example Model, listed under ​ticket 120. Fix: Apply ​patch file via patch -p0 < examplemodel.patch in the top level directory of your Sherpa installation, and recompile the example model in its directory.
• Bugfix to properly include radiation from multiple interactions in the HepEvt? output, listed under ​ticket 127. Fix: Apply ​patch file via patch -p0 < hepevt_interface.patch in the top level directory of your Sherpa installation, and recompile using 'make install'.
• Bugfix to preserve the graviton masses as generated by the MEs according to the ADD model, please cf. ​ticket 126. Fix: Apply ​patch file via patch -p0 < add_masses.123.patch in the top level directory of your Sherpa installation, and recompile by using 'make install'.

Changelog

Bugfixes w.r.t. Version 1.2.2 + patches

Several bugs have been fixed in all parts of the event generation, including the parton shower and ME+PS merging. We strongly recommend upgrading to this newest version where possible.

• ME+PS merging for pure QCD multi-jet production
  There was a mismatch in the application of the ME+PS phase space slicing between ME and parton shower, which became relevant in the case where many partons were involved in a process, e.g. in pure QCD multi-jet production.

New features/Improvements

• POWHEG and MENLOPS
  Weighted event generation according to the POWHEG and MENLOPS approaches is now possible as published in ​arXiv:1008.5399 and ​arXiv:1009.1127. Please contact us if you are interested in using this, as it is not fully documented yet. Corresponding example setups are provided.
• Tunes for different PDF sets
  In addition to the default PDF cteq66 we now also offer an Underlying-Event tuning for the cteq6l1 PDF. Please find the corresponding parameters in the example setup in Examples/Tevatron_UE_CTEQ6L1.
• Custom particle containers
  Sherpa now allows to define custom particle containers, similar to the jets or lepton container. This can be done in the runcard, without altering Sherpa's source code. Please refer to the online manual for details.
• Example interface
  A customizable Sherpa -> HEPEVT converter is included as an example, along with instructions for writing a simple interface to external analyses. The converter itself is suitable for use with the H1 framework.
• Final-state level event selector added, for more information cf. ​ticket 80.
• LHE output