Tags give the ability to mark specific points in history as being important
• v1.0.6   Sherpa Release 1.0.6
96328a50 · ·
Release v1.0.6

# Sherpa 1.0.6

A number of things 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).

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!

To run Sherpa with LHAPDF Version 3 you need to extract the LHAPDF grid archive into the SHERPA-1.0.8/Run directory. (The file size is 40 MB!)

# Major changes with respect to Sherpa-1.0.5

• The multi-cut treatment for the ME-PS merging described in hep-ph/0503281 has been implemented.
• The underlying event has been tuned to fit the Tevatron Run I UE data.
• The phase space integration has been improved further.
• All bug-fixes and patches for version 1.0.5 are included.

# Known problems/known bugs/FAQs

• Problem: Makefile mismatch in module SHERPA-1.0
Eventually leads to untraceable program crash.
Fix: Apply patch file via

patch -p0 < patch_am

in the top level directory of your Sherpa installation

• Problem: Package does not compile with GCC 4.0
Fix: Apply patch file via

patch -p0 < patch_gcc

in the top level directory of your Sherpa installation.

# Some test run output

After installing Sherpa and compiling it via the ./TOOLS/makeinstall script you can check your Sherpa implementation against some test run output we provide for the two default setups.

## Electron photon collision at linear collider:

To obtain this process you simply have to type ./Sherpa in the Run directory of the SHERPA-1.0.6. package.

After executing ./makelibs just call ./Sherpa again and you should obtain the following output:

## W+jet production at Tevatron:

To obtain this process you have to type ./Sherpa PATH=Tevatron1800 in the Run directory of the SHERPA-1.0.6. package.

After executing ./makelibs in the Tevatron1800 directory, execute ./Sherpa PATH=Tevatron1800 again and you should obtain the following output:

• v1.0.7   Sherpa Release 1.0.7
6e98d4c2 · ·
Release v1.0.7

# Sherpa 1.0.7

A number of things 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).

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!

To run Sherpa with LHAPDF Version 3 you need to extract the LHAPDF grid archive into the SHERPA-1.0.8/Run directory. (The file size is 40 MB!)

# Major changes with respect to Sherpa-1.0.6

• tau decays in their full glory with matrix elements and various form factors
• decays of some hadrons as isotropic decays, i.e. only branching ratios
• in SHERPA runs Pythia 6.2 is still default choice for hadron decays.
• Added treatment for decays of heavy unstable particles in MEs.
• All bug-fixes and patches for version 1.0.6 are included.

# Known problems/known bugs/FAQs

• So far, no known bugs.

If you have questions regarding the installation or the usage of Sherpa, which are not answered by our Howto, please look around in this Wiki as well.

• v1.0.8   Sherpa Release 1.0.8
Release v1.0.8

# Sherpa 1.0.8

A number of things 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).

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!

To run Sherpa with LHAPDF Version 3 you need to extract the LHAPDF grid archive into the SHERPA-1.0.8/Run directory. (The file size is 40 MB!)

# Known problems/known bugs/FAQs

• Problem: The implementation of triple and quartic anomalous gauge couplings was partially incomplete and deficient.
Fix: Apply patch file via patch -p0 < AGC.patch in the top level directory of your Sherpa installation.
• Problem: We had a bug in the reweighting of Matrix Elements with the number of strong couplings not being equal to the number of strong particles - 2
Fix: Apply patch file via patch -p0 < oqcd.patch in the top level directory of your Sherpa installation.
• Problem: We had a bug in the Poincare class. This has screwed up some phi distributions to be non-uniform
Fix: Apply patch file via patch -p0 < phi.patch in the top level directory of your Sherpa installation
• Problem: We had an inconsistency in the decays routines for unstable tau-leptons or hadrons originating from other hadron decays
Fix: Apply patch file via patch -p0 < tau.patch in the top level directory of your Sherpa installation.
Fix: Apply patch file via patch -p0 < mi.patch in the top level directory of your Sherpa installation.

If you have questions regarding the installation or the usage of Sherpa, which are not answered by our Howto, please look around in this Wiki as well and post them in the [user:index user section], if they could be of general interest. Bug reports should go directly to the [team:].

• v1.0.9   Sherpa Release 1.0.9
Release v1.0.9

# Sherpa 1.0.9

A number of things 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).

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!

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

To run Sherpa with LHAPDF Version 3 you need to extract the LHAPDF grid archive into the SHERPA-1.0.9/Run directory. (The file size is 40 MB!)

# Known problems/known bugs/FAQs

• Problem: Installation into a specified prefix apart from the default didn't fully succeed.
Fix: Apply patch file via patch -p0 < correct-exec_prefix.patch in the top level directory of your Sherpa installation.
• Problem: Crash during event generation in some vector boson fusion setups.
Fix: Apply patch file via patch -p0 < vbf-merging.patch in the top level directory of your Sherpa installation.
• Problem: Compiling with newer gcc versions fails with Cluster_Partons_Base.H:74: error: invalid pure specifier (only = 0' is allowed) before ';' token.
Fix: Apply patch file via patch -p0 < invalid-pure-specifier-1.0.9.patch
in the top level directory of your Sherpa installation.

If you have questions regarding the installation or the usage of Sherpa, which are not answered by our Howto, please look around in this Wiki as well and post them in the [user:index user section], if they could be of general interest. Bug reports should go directly to the [team:].

• v1.1.0   Version 1.1.0 includes all bugfixes for previous versions as well as new features.
c297bf51 · ·
Release v1.1.0

# Sherpa 1.1.0

Version 1.1.0 includes all bugfixes for previous versions as well as new features (see Changelog below).

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.

# Changelog

## User Interface changes

• Particle properties are no longer specified in Particle.dat and Hadron.dat. Instead they are initialized in the code of the corresponding model and in the fragmentation handler. Overwriting particle/hadron properties is possible in Model.dat/Fragmentation.dat respectively using the tags MASS[<kfcode>]=<mass>, WIDTH[<kfcode>]=<width>, ACTIVE[<kfcode>]=<active>, STABLE[<kfcode>]=<stable> and MASSIVE[<kfcode>]=<massive>. These can also be specified on the command line. Particles and their properties will be displayed during the initialization in output level 2, while hadron properties only get displayed in output level 4.
• QED radiation is turned on by default from the hard process as well as from hadron decays (see new physics modules below). Both of them can be turned off by the switches FS_QED_SCHEME=0 in Shower.dat and YFS_MODE=0 in Fragmentation.dat respectively.
• The b-quark is set massless by default, and is thus contained in the jet container 93.
• The tau-lepton is also set massless by default. Both can be overridden by the above tags.
• Specifying parameters with blanks instead of underscores is not allowed anymore :!: For users owning old setups, we provide a migration script in TOOLS/update_datfiles (see also note about "single file" setup below)
• The parameter Num. Accuracy changes to NUM_ACCURACY. This change is handled by the migration script as well.
• The kf codes have been changed to comply with those given by the PDG. Most importantly, this means W<sup>+</sup> -23 -> 24, W<sup>-</sup> 23 -> -24, Z 24 -> 23, but also many non-SM particles have changed. The migration script also handles their replacement in Processes.dat (but not in Selector.dat or any other files:!:).
• The meaning of the option to specify an electroweak or strong order for a process in Processes.dat has been changed to the exact number which is given. Before, the given number specified the maximum order with which Feynman diagrams were supposed to be generated.
• The parameter to set the SUSY Les Houches accord input file has been changed to SLHA_INPUT (also handled by the migration script).
• The default of the interaction model parameter SIGNAL_MODEL in ME.dat has been changed to the value of the parameter MODEL defined in Model.dat. Accordingly, the MODEL switch now defines both the model parameters and interactions to be initialized. The syntax for the available model implementations can be infered by setting SHOW_MODEL_SYNTAX=1 on the commandline when running Sherpa.

## New physics modules

• AHADIC -- a new fragmentation handler.

## New features

• A new universal selector is provided, based on the Variable class. The variable syntax can be viewed running Sherpa SHOW_VARIABLE_SYNTAX=1. The selector syntax is

"<variable>" <kf1>,..,<kfn> <min1>,<max1>;..;<minn>,<maxn> {<fix#1>,..,<fix#m>}|[<order1>,..,<orderm>]
• Tag replacing in input files is enabled. Tags are specified on the command line using the syntax <Tag>:=<Value>.

• Readers employ fallback settings for input file lookup. The search sequence is

  - PATH
- SHERPA_DAT_PATH/PATH
- SHERPA_DAT_PATH
- <prefix>/share/SHERPA-MC/PATH
- <prefix>/share/SHERPA-MC
• A new option is provided, to set a limit for memory consumption. The corresponding tag on the command line or in Run.dat is RLIMIT_AS. It accepts a pure number, meaning the corresponding fraction of the total memory, a specification in per cent or settings in MB and GB. Examples would e.g. be RLIMIT_AS = 50 % and RLIMIT_AS = 4 GB. Note that the space between the number and the unit is mandatory, even on the command line. By default, the limit is set to the total memory minus 100 MB.
• The grid_makelibs script is provided to allow process code compilation via the Grid see Sherpa Grid page.
• Multithreading in Sherpa can be enabled by

configure --enable-multithread

In the current implementation different threads run in parallel for evaluating hard matrix elements and the corresponding phase space weight. This feature should only be enabled on multi-processor and / or multi-core processor machines. However, so far no significant loss in performance has been observed for single-core single processor computers. The overall computational cost in multithreaded mode is always higher than for single threads, so if only very simple processes are to be evaluated, Sherpa should better be configured for single-threaded mode (the default).

• Dynamic add-on library loading is enabled using the tag SHERPA_LDADD = <libname 1> ... <libname n> in Run.dat or on the command line. Any object provided via getter functions within Sherpa (e. g. models) can thus be dumped into an external library and loaded at runtime. An example can be found [documentation:frameworks:external_rng here]
• PDF information is added to the GenEvent? created by our interface to HepMC2.
• Our interface to HepMC2 also allows for event output according to the HepMC::IO_Ascii format now.
• Algebra interpretation is enabled in Selector.dat and the VarObs in Analysis.dat.
• Interfacing external RNGs is enabled through the External_RNG class. See [documentation:frameworks:external_rng documentation] for details.
• The full setup for Sherpa can be put into a single file using sectioning. The default section, which will be interpreted equivalent to Run.dat starts with (run){ and ends with }(run). The corresponding file can be generated from an existing setup using the TOOLS/update_datfiles script. This script handles the syntax migration as well (see above).
• More reasonable default values in the code for all parameters specified by dat-files.

# 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).
• v1.1.1   Version 1.1.1 includes all bugfixes for previous versions as well as new ones.
e7c2a568 · ·
Release v1.1.1

# Sherpa 1.1.1

Version 1.1.1 includes all bugfixes for previous versions as well as new ones (see Changelog below).

The Sherpa package and a manual for getting started, can be downloaded here:

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

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

# Known problems/known bugs/FAQs

• The compilation of Sherpa on Intel Mac computers may fail due to backtracing not being diabled correctly. Fix: Apply patch file via 'patch -p0 < intel_mac.patch' in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
• The TOOLS/update_datfiles script was missing in the release tarball. You can download it here: {{update_datfiles.sh}}.
• Some incoming particles had the status 1 (active) instead of 2 (decayed) when underlying event was turned on (this should only cause problems if your analysis framework chokes on this). Fix: Apply patch file via 'patch -p0 < particles-status.patch' in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
• Runs with activated Underlying Event might stall with "WARNING in Phase_Space_Handler::WeightedEvent?() : too many trials". Fix: Apply patch file via 'patch -p0 < mpi-stall.patch' in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".

# Changelog

• none

## Bugfixes

• Bugfix for overwriting of particle properties in BSM models.
• Bugfix for "missing flavour" crash when initializing libraries with CKM matrix elements.
• Bugfixes for all-in-one-file setup reading.
• Bugfix for crash of underlying event with some PDFs from LHAPDF.
• Bugfix in parton shower for non-CKKW setups (cures problems with 0 jet setups).
• Bugfix in mass smearing of hadron decays (cures multiplicity problem in pp).
• Some compile fixes for gcc 4.2
• Adjust installation routine for non-standard LHAPDF installations, where the PDFsets are not located in $LHAPDFDIR/share/lhapdf/PDFsets, but somewhere else in$LHAPDFDIR.
• Improvements in the TOOLS/update_datfiles script, which handles the update of dat-files written for 1.0.11.

## New features

(no effect on standard processes, tested)

• Add EPA spectrum for p -> p \gamma
• Update for effective MSSM-higgs gluon couplings; Lorentz structures for A0gg vertices

# 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).
• v1.1.2   Version 1.1.2 includes all bugfixes for previous versions as well as new ones.
0fed6a46 · ·
Release v1.1.2

# Sherpa 1.1.2

Version 1.1.2 includes all bugfixes for previous versions as well as new ones (see Changelog below).

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

• When writing HepMC events, the particle IDs in PdfInfo? have to be PDG IDs, and not -6, ..., 0, ... +6. This is only relevant if the user has been using the PdfInfo? object, or if crashes appear when reading in event files. Fix: Apply patch file via patch -p0 < hepmc-pdfinfo.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
• If explicit mixing of neutral mesons like the B has been turned on, warning messages about unexpected non-fragmentation blobs appear from Hadron_Decays. Fix: Apply patch file via patch -p0 < mixing.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
• The size of the HepEvt? common block initialised by our Lund interface is 4000, but in LHC experiments the convention is 10000. Fix: Apply patch file via patch -p0 < hepevt10k.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
• If Sherpa has been compiled in 32bit mode on a 64bit architecture, the "makelibs" script didn't remember this choice, such that it always tried to produce 64bit process libraries, which produced a crash when Sherpa loaded them. Fix: Apply patch file via patch -p0 < makelibs.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall -t".
• When polarised initial state were considered a problem appeared during process generation and the compilation of libraries. To fix this just apply patch file via patch -p0 < beampol.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
• A certain ordering of MSSM vertices of the type "sfermion-> anti-chargino fermion" was neglected leading to a failure when calculating corresponding decays or processes involving such vertices. To fix this just apply patch file via patch -p0 < susy_vertex.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".
• For some ADD processes the generation of process libraries failed, causing an abort. To fix this just apply patch file via patch -p0 < addfix.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.patch in the top level directory of your Sherpa installation and recompile with "TOOLS/makeinstall".

# Changelog

• None

## Bugfixes

• Hadron property overwriting from the run card or command line didn't work.
• Fix for graviton mass distribution in ADD model.
• Position of decay blobs was not filled.
• Fix for decay treatment in processes with container-particles in the decay only.
• Fix for stalling due to shower rejection in the Underlying Event (error message about "too many trials" from Phase_Space_Handler)
• Fix for rare crashes with "corrupted double-linked list"
• Fix in the locking mechanism of library loading (relevant if you saw crashes during intialization when running Sherpa on a batch system/GRID)

## New features/Improvements

• Improvements in LHAPDF handling:
• For LHAPDF > 5.4.0 use their native fortran wrapper functions
• For all versions use initpdfsetbyname instead of initpdfset such that the path to the PDFsets is determined by LHAPDF itself. This allows you for example to specify the path by the environment variable LHAPATH.
• Make Sherpa relocatable by allowing SHERPA_INCLUDE_PATH, SHERPA_SHARE_PATH and SHERPA_LIBRARY_PATH to be overwritten by corresponding environment variables.
• Improvements in the handling of user-added BSM models with additional massive vector bosons.
• Improvements in HepMC interface:
• Add output class for HepMC::IO_GenEvent format (parameter HEPMC2_GENEVENT_OUTPUT=<filename>).
• Add units information and beam particles to the created HepMC::GenEvent.
• Add event weight to GenEvent? (useful for EVENT_GENERATION_MODE=Weighted)
• Compatibility with gcc 4.3.1
• Resurrected the missing DeltaPhi? and DeltaR selectors
• AHADIC: Improve form of non-perturbative &#945;<sub>s</sub> for splittings according to recent measurements.
• HADRONS: Include form factors for weak hyperon decays.
• Optional on-shell treatment of decays in the hard process.
• Unitarization method for anomalous gauge couplings added (Nucl.Phys.B308:127,1988)
• Slightly changed default values for XS_REGULATION and SCALE_MIN in the underlying event setup to account for changes in hadronisation model.

# 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).
• v1.1.3   Version 1.1.3 includes all bugfixes for previous versions as well as new ones.
3ee14c0e · ·
Release v1.1.3

# Sherpa 1.1.3

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

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.
• 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.
• 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).
• v1.2.0   Version 1.2.0 is a major update of Sherpa which contains many physics improvements and also some minor user interface changes. Correspondingly, the input structure has been improved.
a61a66a1 · ·
Release v1.2.0

# Sherpa 1.2.0

Version 1.2.0 is a major update of Sherpa which contains many physics improvements and also some minor user interface changes. Correspondingly, the input structure has been improved, cf. the online manual and changelog below for a summary of updates.

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:

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.

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. The release has been tested for various processes at hadron colliders, e.g. production of Z+jets, W+jets, pure QCD, di-boson + jets, Higgs through effective couplings, top-pairs, Higgs associated with a top-pair, and also various BSM processes. You can also find examples for non-hadron collider setups.

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

• Sherpa was not compiling with GNU Compiler Collection Version 4.4.0 and higher. Fix: Apply patch file via patch -p0 < gcc-4.4.x.patch in the top level directory of your Sherpa installation, and recompile with make install.
• The NLO example referenced in the Manual was missing in the tarball. Fix: Apply patch file via patch -p0 < nlo-example.patch in the top level directory of your Sherpa installation, and recompile with make install.
• Multi-parton interactions were not working for most BSM models. Fix: Apply patch file via patch -p0 < mpiforbsm.patch in the top level directory of your Sherpa installation, and recompile with make install.
• The status code of some incoming partons was set incorrectly. Fix: Apply patch file via patch -p0 < ispartonstatuscode.patch in the top level directory of your Sherpa installation, and recompile with make install.
• Newer autotools do not allow for duplicate header entries leading to the abort of the installation procedure. Fix: Apply patch file via patch -p0 < dupl_header_remove.patch in the top level directory of your Sherpa installation and recompile with autoreconf -i; ./configure [options...]; make install.
• Vertices for the AGC model are switched off by mistake if certain anomalous couplings are set to zero. Fix: Apply patch file via patch -p0 < agc_fix.patch in the top level directory of your Sherpa installation, and recompile with make install.
• For event generation with disabled METS merging the cross section error estimate might return nan's. Fix: Apply patch file via patch -p0 < xs-error-nan.patch in the top level directory of your Sherpa installation, and recompile with make install.
• In event generation runs with METS merging using AMEGIC, the parton shower might abort with the error message "Missing colour partner". Fix: Apply patch file via patch -p0 < amegic_cluster_1.patch in the top level directory of your Sherpa installation, and recompile with make install.
• There was a newly introduced bug for intermediate gravitons. Fix: Apply patch file via patch -p0 < add_propagator.patch in the top level directory of your Sherpa installation, and recompile with make install.

# Changelog

## User Interface changes

• Online Manual
The online manual described above is also contained in the Manual/ subdirectory of the Sherpa package.
• Matrix-Element generators and processes
With multiple automated Matrix-Element generators available, SHERPA can use any combination of them in the same run, see the description of ME_SIGNAL_GENERATOR in the Manual. To alleviate read-in and to generalise the handling of the various ME generators many of the input parameters in the (processes) section of the input card were renamed. Please refer to the examples and to the Processes section of the online manual for possible changes to your run card.
• Matrix-Element Parton-Shower merging
The merging algorithm is now initialised by the keyword CKKW directly in the merged process specification, followed by the value of the merging cut to be used. The separate specification of a JetFinder? selector is not appropriate anymore and will eventually lead to wrong results. Cf. the description of the CKKW keyword in the Manual.
• Scales and couplings
The setting of factorisation and renormalisation scales has been made clearer and more flexible. Cf. the description of SCALES and COUPLINGS in the Manual.
• Citation recommendations
At the end of each Sherpa run, a file called Sherpa_References.tex is written to disk, containing links to recommended references for the user. Please follow the on-screen instructions to generate a bibtex list of references from this file.
• Internal event record
In line with switching to the new dipole-like Parton-Shower module CSS (see below), the structure of the internal event record has changed such that now only one Blob accomodates the complete Parton-Shower evolution. Initial and final state emissions cannot be disentangled.
• New include structure
If you are maintaining an interface between SHERPA and another software, you will have to make small adjustments to your #include directives. SHERPA sorts its header files into separate directories now, so e.g. #include "Sherpa.H" becomes #include "SHERPA/Main/Sherpa.H". Please contact us, if you need any help with this.
• Example setups
A wide range of example setups is available in the Examples/ directory of the tarball. See also Examples in the Manual for a short description of each of them.

## New features/Improvements

• New Matrix-Element generator
The automated tree-level Matrix-Element generator Comix is included. It is described in detail in JHEP12 (2008) 039 with a brief summary contained in the online Manual.
• New Parton-Shower module
A dipole-like Parton Shower is made the new default shower module of Sherpa, superseeding the old virtuality ordered shower module APACIC++. It is described in detail in JHEP03 (2008) 038 with a short summary given in the online Manual.
• Improved Matrix-Element + Parton-Shower Merging
A new version of the merging algorithm is implemented. It is described in JHEP05 (2009) 053 and also summarised in the Manual together with usage instructions.
• Dipole subtraction for NLO ME's
• FeynRules? interface
An interface to new physics model implementations in the FeynRules? package is provided. For details on FeynRules?, the Sherpa interface and some reference results cf. arXiv:0906.2474. Further details can be found in the Model section of the Manual.
• Hidden Valley parton shower
• YFS for hard leptons
QED corrections to leptons in the hard process are now effected using a YFS type resummation supplemented with a first order correction for hard emissions, as described in JHEP12 (2008) 018. See also Parameters -> QED Corrections in the Manual.
• Rivet interface
It is now possible to run Rivet analyses on top of Sherpa events directly from the Sherpa run card. See Tips and Tricks in the Manual.
• LesHouches? interface for one-loop-amplitudes
• Output of weighted events
It is now possible to output weighted events such that they can be used for an external analysis. This also allows for the consistent inclusion of enhancement factors/functions, e.g. to increase statistics for higher jet multiplicities or in high pT tails.
• Total cross section programmatically accessible
The total cross section for a given simulation is printed at the end of each Sherpa run and can be retrieved online by the user, either through HepMC or directly from the Sherpa instance. Details are given in the Manual.
• v1.2.1   Version 1.2.1 is an update of Sherpa which contains many physics improvements and bugfixes.
b41d19d2 · ·
Release v1.2.1

# Sherpa 1.2.1

Version 1.2.1 is an update of Sherpa which contains many physics improvements and bugfixes. Please see the Changelog below for a summary of updates.

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-1.2.1.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.

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

• HepEvt? translation of QED_Radiation blobs corrected regarding ticket#81. Fix: Apply patch file via patch -p0 < issue_no81.patch in the top level directory of your Sherpa installation, and recompile with make install.
• There was a newly introduced bug for intermediate gravitons. Fix: Apply patch file via patch -p0 < add_propagator.patch in the top level directory of your Sherpa installation, and recompile with make install.

# Changelog

## Bugfixes w.r.t. Version 1.2.0

• Algebra Interpreter
Unary minuses in expressions, partially ignored previously, are now properly taken into account.
• Matrix Element - Parton Shower merging
Certain colour correlations between final states previously not considered in the implementation of the jet criterion are properly accounted for.
• Matrix Element - Parton Shower merging
A problem with the cluster algorithm of AMEGIC++ has been solved that lead to parton shower errors, producing the message Missing colour partner.

## New features/Improvements

• Deep-inelastic scattering simulation
Simulation of deep-inelastic lepton-nucleon scattering is now possible. A first application and an analysis of H1 data are described in detail in arXiv:0912.3715. The corresponding setup is contained in the online Manual.
• ME+PS merging for prompt photon production
Merging of photons produced in real emission matrix elements with photons produced in the interleaved QCD+QED shower cascade has been implemented. Further details and a comparison to LEP and Tevatron data has been published in Phys. Rev. D 81, 034026 (2010).
• HZTool interface
It is now possible to run HZTool analyses on top of Sherpa events directly from the Sherpa run card. See Tips and Tricks in the Manual.
• Automatic setting of coupling information
In collisions with hadronic initial states, the perturbative order and the reference value of the strong coupling are chosen according to the PDF. These settings are printed on-screen during the initialisation phase.
• PDF interfaces
The internal interfaces have been updated to handle CTEQ6.6m/a PDFs, including error sets. MSTW PDFs for different values of &#945;_s can also be used. The default PDF has been changed to cteq66.
• Coupling scale in CSS
The scale for evaluating strong couplings in the initial state shower evolution was changed to account for proper simulation of deep-inelastic scattering.
• Kinematics in CSS
The splitting kinematics in the parton shower simulation have changed according to arXiv:0912.3501 The previous choice can be enabled as an option to study parton shower systematics.
• ME+PS backward clustering improved
In the backward clustering step of the ME+PS merging algorithm we now take into account the shower weight for each potential branching history instead of simply choosing the most probable history.
The fragmentation parameters have been tuned by the Professor team.
• UE tune
Due to the new default PDFs, a new MPI tune became necessary. Using the new parameters 'SCALE_MIN=2.0745' and 'RESCALE_EXPONENT=0.22271' obtained using the Professor tool, we find good agreement with Tevatron underlying event data at 630, 1800 and 1960 GeV.
• Les Houches interface for one-loop amplitudes updated to agree with official proposal in arXiv:1001.1307
• ME Integrator added for weak boson+jets production processes with >=2 jets. For large numbers of jets this integrator is more efficient and simpler than the standard integrator used by AMEGIC++
• v1.2.2   Version 1.2.2 is an update of Sherpa which contains mainly bugfixes.
fc8ae73a · ·
Release v1.2.2

# Sherpa 1.2.2

Version 1.2.2 is an update of Sherpa which contains mainly bugfixes. Please see the Changelog below for a summary of updates.

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-1.2.2.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. If your ticket has been closed and the problem is still unfixed, do not open a new ticket, but reopen the old one.

• Bugfix for unweighted event generation using ME+PS merging, listed under ticket 98. Fix: Apply patch file via patch -p0 < unweighted_events.patch in the top level directory of your Sherpa installation, and recompile with make install.
• There was a newly introduced bug for intermediate gravitons. Fix: Apply patch file via patch -p0 < add_propagator.patch in the top level directory of your Sherpa installation, and recompile with make install.
• 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 with make install.
• Bugfix to preserve the graviton masses as generated by the MEs according to the ADD model, cf. ticket 126. Fix: Apply patch file via patch -p0 < add_masses.patch in the top level directory of your Sherpa installation, and recompile with make install.

# Changelog

## Bugfixes w.r.t. Version 1.2.1

• Running couplings
A problem in the treatment of interferences between graphs with different electroweak/QCD couplings has been solved, see ticket 69.
• Photon ME+PS merging
Photon-quark singularities were not always properly regularised in more complicated matrix elements by the ME+PS merging cut (thanks to Sandrine Laplace for helping in debugging this).
• CS Shower kinematics
The kinematics routines of the CSS are numerically more stable than in previous versions. Some minor bugs, affecting the showering in the presence of massive particles have been fixed, see ticket 60.
• Default scale choice
The kinematics routines of the default scale setter have improved simultaneously, see ticket 70. Also, a bug has been fixed, which only affected runs using AMEGIC with processes based on CSW vertex rules, see ticket 68.
A problem with multithreaded phasespace generation in Comix has been solved, see ticket 75.
A memory leak has been removed in the interface between perturbative and non-perturbative event phases.
• Spin correlations between AMEGIC++ and HADRONS++
Spin correlations between tau leptons produced by AMEGIC++ in the hard process and their decays in the HADRONS++ module had been broken due to an interface change, see ticket 74.
• Beam spectra
Beam spectra like EPA did not work for process groups, i.e. processes involving particle containers like 93. This has been fixed, see ticket 67.
• Cross Sections in Event Generation of pure QCD N>4 Multijet Events with MPI
The inclusive cross section calculated during the generation of pure QCD multijet (N>4) events differend by a few percent depending on whether multi-parton interaction were switched on or off. This has been fixed, see ticket 90.
• QED Radiation from ME in HepEvt? Output
The matrix elmenent QED correction blob was not always properly translated into the HepEvt? output format. This has been fixed, see ticket 81.
• Running Yukawa masses
The running of Yukawa masses is now enabled by default, to make Higgs cross section calculations more meaningful. See ticket 79.
• Parton separation criterion
The interpretation of the value of the merging cut in the processes section has been revised such that it is more similar to the typical hardness as it would be defined by a kT criterion. In 1.2.1 the value was interpreted as twice that, i.e. the matrix element was used down to cuts half as low as intuitively expected.

## New features/Improvements

• Ordered clustering
The parton shower history for truncated shower merging is now constructed in a maximally ordered way.
• Alias particles in hadron decays
It is now possible to define alias particles and their decay tables in the hadron decay module. This allows to define signal decay chains and was a request from LHCb. See ticket 59 for more information.
• Relocatable installation
The Sherpa installation can be made relocatable by specifying the --enable-binreloc configure option.
• NTuple output for NLO Events
A ROOT NTuple output method for matrix element level NLO event generation has been added. See the Manual for details.
• Shortened HepMC2 Output
A shortened HepMC2 output method containing only both beams and the final state stable hadrons has been added. See the Manual for details.
• v1.2.3   Version 1.2.3 is an update of Sherpa which contains bugfixes and new features.
Release v1.2.3

# 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.

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.
• LHE output
• v1.3.0   Version 1.3.0 is an update of Sherpa which contains bugfixes and new features.
Release v1.3.0

# Sherpa 1.3.0

Version 1.3.0 is an update of Sherpa which contains bugfixes and new features. Please see the Changelog below for a complete summary. If you would like to be informed about patches and newer releases, please subscribe to our announcement mailing list.

In can also be accessed via git using

• the web interface
• or git clone -b rel-1-3-0 https://gitlab.com/sherpa-team/sherpa.git for a local clone.

A Manual is included in the Manual/ directory of the tarball. 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 and Results

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.

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.

## 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.

## Changelog

### Bugfixes w.r.t. Version 1.2.3 + patches

Several bugs have been fixed in all parts of the event generation. We recommend upgrading to this newest version where possible.

• Improved kinematics routines for the CSS
The kinematics (re)construction algorithm of the parton shower has been simplified, leading to numerically more stable simulations. This becomes relevant in particular for configurations with low-virtuality t-channel propagators.
• Improved integration routines in Comix
Comix' recursive phase-space generator has been improved by taking more information about currents and connected vertices into account. This is most helpful for processes with many massive propagators.
• Overhaul of internal interpreter
Algebraic expression evaluation in the internal interpreter was made more robust. Several bugs regarding the identification of unary minus signs have been fixed.

### New features/Improvements

• Enhance observable
It is now possible to enhance the generation of phase-space points according to the differential distribution of the process in a particular observable. For details, please refer to the online manual.
• Local definition of ME generator
A new option was introduced to define the desired matrix-element generator process-by-process. This allows, for example, to combine Amegic for the lowest multiplicity with Comix for all higher multiplicities, which becomes relevant in MENLOPS simulations with a large number of jets.
• HepMC output for NLO events
All parts of an NLO matrix element level calculation can be written out in the HepMC format. In particular, correlated real and subtraction events are written out with the same event number, such that their correlation can be taken into account in the analysis.
• v1.3.1   Version 1.3.1 is a bugfix update of Sherpa which does not contain new features.
c86e3755 · ·
Release v1.3.1

# Sherpa 1.3.1

Version 1.3.1 is a bugfix update of Sherpa which does not contain new features. Please see the Changelog below for a complete summary. If you would like to be informed about patches and newer releases, please subscribe to our announcement mailing list.

In can also be accessed via git using

• the web interface
• or git clone -b rel-1-3-1 https://gitlab.com/sherpa-team/sherpa.git for a local clone.

A Manual is included in the Manual/ directory of the tarball. 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.

## Tunes for different PDFs

In addition to the default PDF, we have also tuned Sherpa 1.3.1 with CTEQ6L1 and CT10. Here are the results:

CTEQ6L1:

 K_PERP_MEAN_1 0.573 K_PERP_MEAN_2 0.573 K_PERP_SIGMA_1 0.898 K_PERP_SIGMA_2 0.898 PROFILE_PARAMETERS 0.884 0.828 RESCALE_EXPONENT 0.244 SCALE_MIN 2.65 SIGMA_ND_FACTOR 0.788

CT10:

 K_PERP_MEAN_1 1.17 K_PERP_MEAN_2 1.17 K_PERP_SIGMA_1 0.760 K_PERP_SIGMA_2 0.760 PROFILE_PARAMETERS 0.576 0.353 RESCALE_EXPONENT 0.238 SCALE_MIN 2.52 SIGMA_ND_FACTOR 0.465

## 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.

• Suppressing unitarisation output in SM+AGC model, not currently listed on the bug tracker. Fix: Apply patch file via patch -p0 < AGC-output.patch in the top level directory of your Sherpa installation, and recompile using 'make install'.

## Changelog

### Bugfixes w.r.t. Version 1.3.0

All patches available for previous versions are included in this release:

• Bugfix for MPI shower setup and corresponding new tune
• Bugfix for MPI initialization and QCD simulations
cf. ticket 180
• Bugfixes for ME level NLO event generation

### New features/Improvements

• None
• v1.4.0   Version 1.4.0 is a major update of Sherpa which contains several new features.
f7f76de0 · ·
Release v1.4.0

# Sherpa 1.4.0

Version 1.4.0 is a major update of Sherpa which contains several new features. Please see the Changelog below for a complete summary. If you would like to be informed about patches and newer releases, please subscribe to our announcement mailing list.

In can also be accessed via git using

• the web interface
• or git clone -b rel-1-4-0 https://gitlab.com/sherpa-team/sherpa.git for a local clone.

A Manual is included in the Manual/ directory of the tarball. 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.

## Patches/known problems/known bugs/FAQs

All known problems/questions and their solutions can be found on our issue tracker (please log in with username "user" and password "sherpa"). If you encounter any problem while installing or running Sherpa, please open a new issue in the tracker.

## Changelog

### Bugfixes

All patches available for previous versions are included in this release

### New features/Improvements

• v1.4.1   Version 1.4.1 is a bugfix release of Sherpa which does not contain any new features compared to 1.4.0.
Release v1.4.1

# Sherpa 1.4.1

Version 1.4.1 is a bugfix release of Sherpa which does not contain any new features compared to 1.4.0. Please see the Changelog below for a complete summary of the changes. If you would like to be informed about patches and newer releases, please subscribe to our announcement mailing list.

In can also be accessed via git using

• the web interface
• or git clone -b rel-1-4-1 https://gitlab.com/sherpa-team/sherpa.git for a local clone.

A Manual is included in the Manual/ directory of the tarball. 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.

## Patches/known problems/known bugs/FAQs

All known problems/questions and their solutions can be found on our issue tracker (please log in with username "user" and password "sherpa"). If you encounter any problem while installing or running Sherpa, please open a new issue in the tracker.

## Changelog

### Bugfixes

• Vertex offsets of hadron decays were missing in events with multiple "partonic" hadron decays. This becomes relevant when a detector simulation sensitive to vertex offsets is applied to the events and can impair the b-tagging performance.
• Fixes for build failures for gcc 4.7, and in the Manual subdirectory, and with svn.make (cf. #228).
• Bugfix for symmetry factor, cf. #172
• Restriction of t-channels can be optionally limited to EW t-channels only. This is necessary for using this restriction in ME+PS merged samples. Nothing changes for the default (no t-channel restriction).
• Consistency in the non-default EW_SCHEME's. Again, no changes for the default setup (EW_SCHEME=0).

### New features

• None
• v1.4.2   Version 1.4.2 is a convenience and bugfix release of Sherpa. The main new feature compared to 1.4.1 is the introduction of the TUNE parameter which can be set to NNPDF23, NNPDF23_UEup, NNPDF23_UEdown, CT10, CT10_UEup, and CT10_UEdown. The CT10 option is the default setting (no change to 1.4.1), NNPDF23 provides settings for NNPDF 2.3, and the UEup and UEdown variants change the underlying event activity by +/-10%.
f5d90c0f · ·
Release v1.4.2

# Sherpa 1.4.2

Version 1.4.2 is a convenience and bugfix release of Sherpa. The main new feature compared to 1.4.1 is the introduction of the TUNE parameter which can be set to NNPDF23, NNPDF23_UEup, NNPDF23_UEdown, CT10, CT10_UEup, and CT10_UEdown. The CT10 option is the default setting (no change to 1.4.1), NNPDF23 provides settings for NNPDF 2.3, and the UEup and UEdown variants change the underlying event activity by +/-10%.

Please see the Changelog below for a complete summary of the changes. If you would like to be informed about patches and newer releases, please subscribe to our announcement mailing list.

In can also be accessed via git using

• the web interface
• or git clone -b rel-1-4-2 https://gitlab.com/sherpa-team/sherpa.git for a local clone.

A Manual is included in the Manual/ directory of the tarball. 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.

## Patches/known problems/known bugs/FAQs

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

## Changelog

### Bugfixes

• Bugfix for CA flavour sorting, cf. #242
• bugfix for NLO with universal selector

### New features

• New TUNE parameter
• v1.4.3   Version 1.4.3 is a convenience and bugfix release of Sherpa.
a1c37cd2 · ·
Release v1.4.3

# Sherpa 1.4.3

Version 1.4.3 is a convenience and bugfix release of Sherpa. Please see the Changelog below for a complete summary of the changes. If you would like to be informed about patches and newer releases, please subscribe to our announcement mailing list.

In can also be accessed via git using

• the web interface
• or git clone -b rel-1-4-3 https://gitlab.com/sherpa-team/sherpa.git for a local clone.

A Manual is included in the Manual/ directory of the tarball. 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

### Bugfixes

• Factorisation scale reliably stored in event record now

### New features

• The minimal invariant mass allowed for any pair of particles in the hard scattering can now be adjusted with the parameter INT_MINSIJ_FACTOR=1.e-12, which will be multiplied with E_CMS^2 to implement the numerical cut-off.
• Yukawa couplings in the Two-Higgs-Doublet-Model made more flexible
• v1.4.5   Version 1.4.5 is a bugfix release of Sherpa.
53c1729c · ·
Release v1.4.5

# Sherpa 1.4.5

Version 1.4.5 is a bugfix release of Sherpa. Please see the Changelog below for a complete summary of the changes. If you would like to be informed about patches and newer releases, please subscribe to our announcement mailing list.

In can also be accessed via git using

• the web interface
• or git clone -b rel-1-4-5 https://gitlab.com/sherpa-team/sherpa.git for a local clone.

A Manual is included in the Manual/ directory of the tarball. 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

Note that this release is identical to 1.4.4 except for one changeset which was accidently missing in the original 1.4.4 tarball. The following changes are listed with respect to version 1.4.3:

### Bugfixes

• Bugfix in amplitudes containing effective-theory couplings to the Higgs boson
• Bugfix for issue in hadron decays: Some exotic particles were accidently produced and left stable without warning
• Compile fixes for MacOS and gcc 4.7 compatibility
• Improved multipole radiation pattern for ME QED corrections in the YFS approach

### Other changes with respect to 1.4.3

• The default for the parameter UNITARIZATION_N in the model implementation of anomalous gauge couplings now has a default of '2' (instead of disabling unitarization by the previous default of '0')
• v2.0.0   Version 2.0.0 is the first NLO version of Sherpa. The main new feature compared to the 1.4.x series is the introduction of [email protected] merging. This release improves upon the previous beta series by an extension of its physics capabilities and an extensive validation of all features already present in the 1.4.x series.
24690d2c · ·
Release v2.0.0

# Sherpa 2.0.0 (Annapurna)

Version 2.0.0 is the first NLO version of Sherpa. The main new feature compared to the 1.4.x series is the introduction of [email protected] merging. This release improves upon the previous beta series by an extension of its physics capabilities and an extensive validation of all features already present in the 1.4.x series.

If you spot any problem, please send us an email or open an issue in gitlab. This will allow us to reach a mature version of the generator, suitable for all physics analyses. If you would like to be informed about patches and newer releases, please subscribe to our announcement mailing list.

In can also be accessed via git using

• the web interface
• or git clone -b rel-2-0-0 https://gitlab.com/sherpa-team/sherpa.git` for a local clone.

A Manual is included in the Manual/ directory of the tarball. 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.

## Patches/known problems/known bugs/FAQs

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