Tags give the ability to mark specific points in history as being important
  • v2.2.4   Release version 2.2.4

    Sherpa 2.2.4

    Version 2.2.4 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.

    Download

    The Sherpa package can be downloaded here:

    SHERPA-MC-2.2.4.tar.gz

    In can also be accessed via git using

    • the web interface
    • or git clone -b rel-2-2-4 https://gitlab.com/sherpa-team/sherpa.git 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.

    References

    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.

    Examples

    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.

    Changelog

    Known issues

    • As all releases in the v2.2.x series, dijet production using the multi-jet merging algorithm is broken, see #46. This is fixed in the upcoming v3.0. If you can not wait for it, you can use a v2.1.x release.

    Interface changes

    • New default parameters for hadronisation model to improve heavy flavour production fractions and meson/baryon ratios (thanks to Andrii Verbytskyi).
    • Updates to Recola interface with some new parameter (names), please refer to the manual.
    • Make STRICT_METS the default scale setter to guarantee full scale setting accuracy for unweighted events.

    New features

    • Availability of DIRE NLO parton shower (cf. arXiv:1705.00742). This is not (yet) the default shower, in particular not in NLO-merged configurations.
    • Higher numerical stability in parton shower kinematics (re)construction.
    • Add OVERWEIGHT_THRESHOLD allowing user to cap maximal weight during event generation (cf. manual).
    • Avoid spuriously large weights in NLO-merged samples due to instable PDF ratios.
    • Add interface for hadron-level selectors.
    • Add Max_N_TChannels option in Amegic.
    • Add possibility to identify partons which originate in the hard decay handler.
    • Restructure gzip support such that it can be switched off at runtime (USE_GZIP).
    • Enable on-the-fly reweighting for calculations with the Higgs (Interference) add-on for HIGGS_INTERERENCE_MODE 1, 2, 3 or 4.

    Bugfixes

    • Bugfix in NLO-matched parton shower emission for non-trivial colour structures like in V+2j@NLO. This fixes an eta asymmetry which was visible at the ~2% level in such samples.
    • BSM models through UFO: fix running coupling behaviour and treatment of exotic color octets.
    • Bugfix in random generator for Poisson distributions with large mean values.
    • Bugfixes for segfaults and compiler warnings with gcc 7.1.
    • Bugfix for colour assignment in clustering for loop-induced merged processes.
    • Bugfix for decay showering in conjunction with NLO+PS matching.
  • v2.2.5   Release version 2.2.5
    786afa42 · bugfix in D_CC.C ·

    Sherpa 2.2.5

    Version 2.2.5 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.

    Download

    The Sherpa package can be downloaded here: SHERPA-MC-2.2.5.tar.gz

    In can also be accessed via git using

    • the web interface
    • or git clone -b rel-2-2-5 https://gitlab.com/sherpa-team/sherpa.git 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.

    References

    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.

    Examples

    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.

    Changelog

    Known issues

    • As all releases in the v2.2.x series, dijet production using the multi-jet merging algorithm is broken, see #46. This is fixed in the upcoming v3.0. If you can not wait for it, you can use a v2.1.x release.

    Interface changes

    • Add preliminary support for HepMC3 (this interface is still being tested)

    New features

    • Improve decay showering off top quarks
    • Improve single-top support and add examples and documentation for its production channels
    • Improve hadronisation and hadron decays for heavy flavour production
    • Introduce a user hook framework which allows users to easily implement event generation afterburners, see Examples/Userhook
    • Add settings to output ME-only on-the-fly variations (along with the full ones):
      HEPMC_INCLUDE_ME_ONLY_VARIATIONS=1 (HepMC interface)
    • New cut-off for parton-shower reweighting:
      CSS_REWEIGHT_SCALE_CUTOFF=<pt_min>, default: 5 GeV^2
      this is more generally applicable than using a cut-off on the number of reweighted emissions
    • Improve support for on-the-fly variations of clustering steps (reweight each step locally instead of doing it globally)

    Bugfixes

    • Fix issue with the overweight treatment for negative weights
    • Add missing shower weight in some event outputs, e.g. when using OUTPUT HepMC...[]
    • Fix issue with the overweight threshold for on-the-fly variations
    • Fix issue with non-trivial beam spectra handling
    • Fix possible issues with electron-"PDF" initialization
    • Fix issue with the ISR-channel threshold for leptonic collider
    • Fix X/Y functions in METOOLS (this is relevant for hadron decays)
    • Fix crash in decay-channel sorting
    • Fix crash when using EVENT_TYPE=HadronDecay
    • Fix issue with CSS strong coupling values when using non-trivial scale factors
    • Fix issue with QSF variations for real emission calculations with COMIX
    • Fix crash when doing on-the-fly variations and invalid dipole kinematics occur
    • Fix issue in the interplay of the flux and the BIWeight for 1->n processes
    • Fix issue when using vertices with a vanishing coupling
    • Fix rare "invalid amplitude" crashes
    • Fix issues when adding limits for the number of t-channel propagators in matrix elements
    • Fix issue with checking PDF availability when enforcing jet vetoes
    • Fix several compilation issues
  • v2.2.6   Release version 2.2.6
    5cf79907 · implemented the above fix ·

    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.

    Download

    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 https://gitlab.com/sherpa-team/sherpa.git 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.

    References

    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.

    Examples

    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.

    Changelog

    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

    Enhancements

    • 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
  • v2.2.7   Release version 2.2.7

    Sherpa 2.2.7

    Version 2.2.7 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.

    Download

    The Sherpa package can be downloaded here: SHERPA-MC-2.2.7.tar.gz

    In can also be accessed via git using

    • the web interface
    • or git clone -b rel-2-2-7 https://gitlab.com/sherpa-team/sherpa.git 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.

    References

    The main reference for Sherpa 2.2.x is arXiv:1905.09127. Please cite this publication if you have used Sherpa 2.2.x 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.

    Examples

    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.

    Changelog

    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

    Enhancements

    • Add tools needed for the variable flavour number scheme in the multi-jet merging, cf. arXiv:1904.09382 (!146)
      • Add an option to cluster RS events in a fully ordered way (set COMIX_CLUSTER_RS_ORDERED=1)
      • Add a new scale scheme to the CS shower which should give better results for g->QQ splitting
      • Introduce a new scale tag P_TM2 defined as the root of the product of all transverse masses of all massive particles
    • Introduce new shower evolution schemes that take masses into account (set CSS_EVOLUTION_SCHEME=2 or 3) (!139)
    • Update default Lund string fragmentation parameters (!177)
    • Support the new analysis option feature in Rivet within the internal Rivet interface (!168)
    • Improve support for OpenLoops 2
    • Add an option to steer the total number of events generated in MPI event generation runs (!172)
    • Apply shower renormalisation scale factor to the strong coupling argument instead of re-defining AlphaS(mZ) (this improves the consistency of variations within Sherpa) (!145)
    • Add an option to switch on/off the multiple interaction library output (set MI_GENERATE_RESULTS_DIRECTORY=1 or 0) (!165)
    • Add an option to let the strong coupling value used in the shower freeze at a value of 1 instead of being cut off for low scales (this can mitigate cut-off issues when reweighting parton-shower emissions, cf. the manual) (!131)

    Bugfixes (runtime issues)

    • Fix wrong eikonals in the top-decay showering (#176)
    • Fix issues in the CS shower emission reweighting (!131)
      • Fix max coupling setting for renormalisation scale reweighting
      • Fix reweightings below the accepted emission scale
      • Ignore reweightings if the target strong coupling value is zero (due to a different cut-off, this improves the statistics of the reweighted event sample)
    • Adjust hadron masses correctly when providing custom masses via MASS (!156)
    • Fix an issue with the VAR scale setter if its value was based asymmetrically on parton momenta (!141)
    • Fix broken IGNOREBEAMS switch for the internal Rivet interface (!148)
    • Use status code 11 for incoming particles with a strong charge for the HepMC_Short output format (this improves comptability with Rivet)

    Bugfixes (compilation issues)

    • Replace C++ MPI bindings with C MPI bindings (C++ bindings were deprecated a long time ago and are not enabled per default in OpenMPI 4 (#77)