Version 1.1.3 includes all bugfixes for previous versions as well as new ones.

Sherpa 1.1.3

Version 1.1.3 includes all bugfixes for previous versions as well as new ones (see Changelog below).

Download of Sherpa 1.1.3

The Sherpa package and a short primer on how to get started, can be downloaded here:

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.

:!: Please note that you still have to apply any patches provided below after unpacking the tarball.

Patches/known problems/known bugs/FAQs

  • Decay vertex positions have been set incorrectly for hadrons produced in a hadron decay. Fix: Apply patch file via patch -p0 < decay-vertex-position.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
  • Decay vertex positions have also been set incorrectly for partonic hadron decays with subsequent shower/fragmentation. Fix: Apply patch file via patch -p0 < partonic-decay-vertex-position.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
  • When writing events to native Sherpa output, the event weight was always written as 1. This only affects users who run in EVENT_GENERATION_MODE=Weighted or use Enhance_Factors in their processes setup, and write events using SHERPA_OUTPUT. Fix: Apply patch file via patch -p0 < sherpa-weight.1.1.3.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
  • The 4th Generation Extension to the Standard Model was not properly initialising itself. All other models were unaffected. Fix: Apply {{4thGen.patch|patch file}} via patch -p0 < 4thGen.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
  • An error occured when performing an internal test during the process library generation for processes that include vertices with epsilon tensors. Fix: Apply patch file via patch -p0 < epsilon_string_test_fix.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
  • Compilation fails when linking to the newly released HepMC 2.05. Fix: Apply patch file via patch -p0 < hepmc-2.05.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
  • Different sizes of the HepEvt? common block are required by different experiments. The HepEvt? common block size can therefore be set as a configure-option: --enable-hepevtsize=HEPEVT_SIZE. To enable this feature apply patch file via patch -p0 < configurable_hepevt_cb_size_113.patch in the top level directory of your Sherpa installation, run "autoreconf -fi", configure using "./configure [OPTIONS]" and recompile with "TOOLS/makeinstall". Alternatively "./TOOLS/makeinstall -t --copt [CONFIGURE_OPTION] can be used to configure and compile.

Changelog

User Interface changes

  • By default, the Lund interface for fragmentation and hadron decays is deactivated during compilation now. If wanted, it has to be activated during compilation by the configure flag --enable-pythia. This will simplify compilation for all users who don't need this interface.
  • HepEvt? common block size changed to 10000 to comply with other generators (only relevant if Pythia has been enabled during compilation).
  • Default precision for writing numbers into event output files has been changed from 6 two 12 significant digits. This setting can be changed by the parameter OUTPUT_PRECISION.
  • We have prepared an updated publication covering all aspects of event generation with Sherpa. The preprint is already available on arXiv:0811.4622. Please cite this publication if you have used Sherpa for your studies.

Bugfixes

  • Fix for an inconsistency when attempting to do scale variations using the parameter SCALE_FACTOR (for the initial cross section evaluation factorisation scale variation was ignored before).
  • Fix for compilation problem of libraries when polarised initial states were considered.
  • Fragmentation handler now correctly reads hadronisation parameters from fragmentation section instead of Cluster.dat
  • When writing HepMC events, the particle IDs in PdfInfo? have to be PDG IDs, and not -6, ..., 0, ... +6.
  • Fix for incorrect warning messages when explicit mixing of neutral mesons was active.
  • Certain ordering of the MSSM coupling "sfermion -> chargino fermion" were ignored in the process generation.
  • Print_Graphs issue fixed (https://projects.hepforge.org/sherpa/trac/ticket/31)
  • A crash while generating ADD Libraries has been fixed.
  • Fix for inconsistent event record when showering intermediate resonances.
  • Fix for crash in runs without CKKW merging due to missing shower cleanup.

New features/Improvements

  • New Tevatron data has been used to further validate and tune Sherpa by revising some of the default choices of the implemented merging procedure. Since this involves PDF scales, cross sections for the hard process may change within the limits appropriate for leading order calculations.
  • Reliable installation on MacOS.
  • New option for hadron mass smearing: Smear all hadrons or smear only unstable hadrons.
  • Proper signal handling for writing (e. g. events) into a named pipe.
  • Added optional versioning to build system which allows Sherpa's executables, libraries, includes and share-files to be installed with version tags, such that multiple Sherpa versions can live in the same installation prefix.
  • Variable selector made usable for one particle cuts.

Remarks

For process declarations a specific ordering is needed:

  • For electron-photon collisions make sure the photon is on the first beam, bunch and parton!
  • For electron-proton collisions make sure the electron is on the first beam, bunch and parton!

A few non-standard setups are not working. Do not even try:

  • Parton shower in DIS--like situations, i.e. with only one incoming leg that showers.
  • Substructure of photons.
  • Laser backscattering beyond the region where CompAZ is valid (up to 500 GeV).