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NEWS
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Herwig News -*- outline -*-
================================================================================
* Herwig 7.3.0 release: 2023-12-11
** electroweak radiations added to the default parton shower
** HQET spin hadronization and decay have been implemented to improve the predictions of excited heavy mesons and heavy baryons
** dot-preserving treatment of the default parton shower evolution scale has been implemented
** infrastructure for dynamic hadronization model and dark hadronization added
** kinematic treatment of cluster splitting in cluster fissioner improved
** new global tune implemented
** several bugs fixed
* Herwig 7.2.3 release: 2022-04-30
** improved ufo2herwig tool
** improved remnant handling for photon collisions
** improved high-energy behaviour of default parton shower
* Herwig 7.2.2 release: 2021-01-22
** support for python 3 and gcc 10
** ufo2herwig script is updated to be compatible with python 2 and 3, using --convert option
* Herwig 7.2.1 release: 2020-04-10
** vertex position fix for taus in dipole shower events
* Herwig 7.2.0 release: 2019-12-09
** improvements to the simulation of multiple-parton interactions, including diffractive processes
** a new model for baryonic colour reconnection
** spin correlations in both the dipole and angular-ordered parton showers
** improvements to strangeness production
** an improved choice of evolution variable in the angular-ordered parton shower
** support for generic Lorentz structures in BSM models.
* Herwig 7.1.7 release: 2020-04-10
** vertex position fix for taus in dipole shower events
* Herwig 7.1.6 release: 2019-12-11
** fix if no W in top in external events
** vertex position fix for dipole shower events
** update boost m4
** add max,min, re, im to functions for ufo conversion
** comparision operators should be const, issues with C++17, thanks to Ivan Razumov (GENSER)
* Herwig 7.1.5 release: 2019-04-04
** Add option of producing partons on physically mass shell after the parton shower
to allow the string model to be used to hadronize events
** Fixes for template issues and compiler warnings for gcc8,9, icc and clang
** Fixes to the calculation of W, Z and h widths if decay modes removed
** Fix typo in FI g to gg dipole.
** Fix to allow 1 parameter to specify the mass of more than one particle in the UFO converter
** Fix to partial width calculation of VSS decays
** Fix the PDF assignment for DIS processes with Matchbox
** Fix for undecayed W bosons in internal POWHEG gauge boson pair code
** Update boost detection in configure script
* Herwig 7.1.4 release: 2018-06-28
** More matrix elements and better handling of BSM physics
** Fix for spin correlations in angular-ordered shower, effects top decays
** Allow fixed target collisions
** various minor fixes
* Herwig 7.1.3 release: 2018-04-05
** Dipole Shower
*** Changed default phase space limits
*** g -> gg splitting function asymmetrized
*** Initial retune supplied, given the visible changes
to LEP observables
** Added new Baryonic colour reconnection model
(arXiv 1710:10906)
** Added Schuler-Sjostrand Photon PDFs
** Handling of massless taus from external sources
** various minor fixes
** use std::array<> where possible
* Herwig 7.1.2 release: 2017-11-01
** Reduction of the default pt cut for QED radiation off leptons.
** Inputfile changes due to new read mode in ThePEG.
ThePEG remains in current repo dir when reading input-file/snippet.
** Fix for shower scale variations in qtilde shower.
** All standard input files now use the tuned intrinsic pt.
** Remove obsolete input files for various tunes.
** Fix for Madgraph interface for NLO corrections with recent version.
** Run file size reduction for processes using madgraph/openloops.
** Fix in jacobian for massive dipole kinematics.
** General improvements for UFO model handling.
* Herwig 7.1.1 release: 2017-07-14
** Snippets are now all installed
** Fixed broken ufo2herwig output and LHC-MB.in
** UFO improvements
*** More robust SLHA file handling
*** option of creating diagonal mixing matrices, needed for ATLAS simplfied models
*** Improved warnings about resetting standard model particles
*** Fixed certain cases where the wrong lorentz structure was picked in VVS vertices
** Improved error message for unhandled beam particles
** Fix for Dipole Shower chain selection
** Fixed crash in double diffractive delta resonances
* Herwig 7.1.0 release: 2017-05-19
** Major new release
For a more detailed overview and further references please see the
release note arXiv:1705.06919
** NLO multijet merging with the dipole shower
** A new soft model
** An interface to EvtGen
** Improved calculation of mass effects in the dipole shower
** Top decays in the dipole shower, and NLO corrections to the decay
** An implementation of the KrkNLO method for simple processes
** Major restructuring and cleanup of default input files
** C++11 is now mandatory and heavily used in the code
** Many smaller bugfixes and improvements
* Herwig 7.0.4 release: 2016-10-24
** API
The high level API is now properly available as a library, providing an
alternative to the Herwig main program.
** Dipole shower
Added nloops() function to the AlphaS classes to return the number of loops
in the running coupling
** Matchbox
Improved error handling and clearer messages
** BSM models
Initialize W mass correctly from SLHA file. Improved reading in of decay
modes if they already exist.
** Sampling
Introduced option to reduce reference weight in AlmostUnweighted mode by
Kappa factor. Useful for processes where full unweighting is infeasible.
** Qtilde shower
Better control of scale in splitting functions using the
SplittingFunction:ScaleChoice interface.
** Tests
New NLO fixed-order input files for testing Matchbox in Tests/ExternNLO.
** Input files
Set diagonal CKM options consistently. Added TauTauHVertex and MuMuHVertex
to MatchboxDefaults.
* Herwig 7.0.3 release: 2016-07-21
** subprocess generation filters
A number of filters has been implemented to speed up process and diagram
generation for the case of Standard Model like processes; this is
particularly helpful for processes involving a large number of electroweak
combinatorics. See the documentation for more details.
** fix to directory hierarchy
A bug in the Herwig-scratch directory hierarchy when integrating with
different seeds has been fixed.
** fix for relocating MadGraph generated amplitudes
The directory and symbolic link structure for MadGraph-built amplitudes has
been changed to allow for relocation of a run directory to a different file
system hierarchy.
** z* variable added to LeptonsJetsAnalysis
The builtin LeptonsJetsAnalysis has been extented to include the normalized
relative rapidity z*
** detuning parameter for shower reweighting
An efficiency tweak when using the shower reweighting facilities has been
introduced for the veto algorithms in both the QTilde and the Dipole
shower. See the documentation for more details.
** BaryonThreeQuarkModelFormFactor
A scaling bug in the form factor series expansion was fixed.
* Herwig 7.0.2 release: 2016-04-29
** Event reweighting
New option of calculating the weights for the effect of varying the scale
used in both the default and dipole showers. The method is described in
arXiv:1605.08256
** mergegrids mode
A main mode for the Herwig executable has been added which merges the
integration grids from parallel runs.
** NLO Diphoton production
The NLO matrix elements in the POWHEG approach for diphoton production as
described in JHEP 1202 (2012) 130, arXiv:1106.3939 have been included as
MEPP2GammaGammaPowheg.
** BSM Hard process constructor
A missing Feynman diagram with a t-channel vector boson has been added to
the matrix element for vv2ss
** BSM Decay Modes calculation
The behaviour of the option to disable decay modes in BSM Models has been
changed so that the partial width for the ignored modes is now calculated
and included in the total width, but the branching ratio is set to
zero. This is more physical than the previous option where the mode was
t otally ignored and hence not included in the calculation of the width.
** Mass Generation
The behaviour of the GenericMassGenerator has been changed so that modes
which have been disabled are only included in the calculation of the total
width and not in the partial width used in the numerator of the weight used
to select the off-shell mass.
** Boost detection
Boost could not detect the compiler version for gcc-5.3 and gcc-6.1
* Herwig 7.0.1 release: 2016-01-17
** Version number written to log file
The Herwig version number is now included in addition to ThePEG's version.
** Tau lifetimes
A bug with lifetimes for hard process Taus is fixed. Thanks to ATLAS
for the report!
** Shower FSR retries
Rare events could take a long time due to an extremely large number
of FSR retries. These are now capped at a configurable number.
** Dipole shower
Reweighting for non-radiating events; fixes for shower profile
handling; option to downgrade large-Q expansion for alphaS
** Matchbox builtins
Added massive currents for q-qbar
** ShowerAlphaQCD
can now use user-defined thresholds
** Input snippets
W/Z/H on-shell now split into three files; 4-flavour scheme added
** UFO converter
The converter now has experimental support for writing out param
cards of its current settings.
** LEPJetAnalysis loading fixed
** Contrib
HJets++ has moved to a stand-alone project, FxFx has been added
* Herwig 7.0.0 (Herwig++ 3.0.0) release: 2015-12-04
** Major new release
A major new release of the Monte Carlo event generator Herwig++ (version
3.0) is now available. This release marks the end of distinguishing
Herwig++ and HERWIG development and therefore constitutes the first major
release of version 7 of the Herwig event generator family. The new version
features a number of significant improvements to the event simulation,
including: built-in NLO hard process calculation for all Standard Model
processes, with matching to both angular ordered and dipole shower modules
via variants of both subtractive (MC@NLO-type) and multiplicative
(Powheg-type) algorithms; QED radiation and spin correlations in the
angular ordered shower; a consistent treatment of perturbative
uncertainties within the hard process and parton showering, as well as a
vastly improved documentation. This version includes (for a more detailed
overview and further references please see the release note
arXiv:1512.01178):
** A long list of improvements and fixes for the Matchbox module
*** includes MC@NLO and Powheg matching to both showers with truncated showering
** A long list of improvements and fixes for both of the shower modules
*** includes improvements of numerics issues relevant to 100 TeV pp collisions
** NLO event simulation and Matchbox development
*** Interfaces to a number of external libraries
*** A new workflow for event generation
*** Electroweak corrections to VV production
** Parton shower development
*** QED radiation in the angular ordered shower
*** Spin correlations in the angular ordered shower
*** New scale choices in gluon branchings
** Improvements to event generation workflow
*** Re-organized and streamlined input files for the new NLO development
*** A unified treatment of shower and matching uncertainties
*** New integrator modules featuring parallel integration
** New default tunes for both shower modules
** New contrib modules
*** Electroweak Higgs plus jets production
*** FxFx merging support
*** Higgs boson pair production
* Herwig++-2.7.1 release: 2014-07-07
** New shower switches to select schemes for momentum reconstruction
*** QTildeReconstructor:FinalStateReconOption
has the following options:
*** Default
All momenta are rescaled in the rest frame.
*** MostOffShell
Put all particles on the new-mass shell and the most off-shell and
recoiling system are rescaled to ensure 4-momentum is conserved.
*** Recursive
Recursively put the most off-shell particle which hasn't yet been
rescaled on-shell by rescaling the particles and the recoiling
system.
*** RestMostOffShell
The most off-shell is put on shell by rescaling it and the
recoiling system, the recoiling system is then put on-shell in its
rest frame.
*** RestRecursive
As above, but recursively treat the currently most-off shell
(only makes a difference for more than 3 partons)
** Ticket #378: Hadronization of baryon number violating clusters involving diquarks
Fixed by only considering non-diquarks to be combined in the
ClusterFinder.
** UFO converter can now parse SLHA files for parameter settings
The UFO converter code can now use SLHA files for modifying
parameters. The first pass "ufo2herwig" produces the model to be
compiled. For each parameter card, run "slha2herwig" to get the
matching input file.
** Fix for systems using lib64
The repository is now initialized correctly on systems using lib64
as the library location.
** Efficiency optimization
Better allocation of internal vector variables for a noticeable
speed increase of 10-20% with LHC events.
* Herwig++-2.7.0 release: 2013-10-28
** UFO interface to Feynman rules generators
Herwig++ now includes "ufo2herwig", a tool that automatically
creates all required files to run a BSM model from a UFO
directory. The conversion has been extensively tested against
Feynrules models MSSM, NMSSM, RS, Technicolor,
and less extensively with most of the
other models in the Feynrules model database.
We expect that following this release there will be no further
hard-coded new physics models added to Herwig++ and that future
models will be included using the UFO interface.
** Shower uncertainties
A first set of scaling parameters to estimate shower uncertainties
is provided for both the angular ordered as well as the dipole
shower; they are Evolver:HardScaleFactor and ShowerAlphaQCD:
RenormalizationScaleFactor.
** Rewrite of Matchbox NLO matching
The NLO matching implementation has been rewritten and is now more
flexible and consistent. Profile scales are provided for the
hardest emission both for the dipole shower and matrix element
correction matching.
** BLHA2 Interface and new processes
Matchbox now features a generic BLHA2 interface to one-loop
amplitude codes and now also includes W and W+jet production as
well as Higss production in gluon fusion as builtin processes.
** Impoved dipole shower kinematics parametrization
The kinematics parametrization for emissions in the dipole shower
has been made more efficient.
** W and Z Powheg decays
Decays of W and Z bosons now use the Powheg decayers by default.
** Improved treatment of beam remnants
The handling of beam remnants has been improved in multiple
contexts, leading to a much lower error rate at p+/p- collisions.
An additional value "VeryHard" for ClusterFissioner:RemnantOption
can be used to disable any special treatment of beam remnant
clusters.
** New underlying event tune
Herwig++ now uses tune UE-EE-5-MRST by default. Other related tunes
can be obtained from the Herwig++ tunes page
** Improvements in BSM code
The UFO development identified many sign fixes in rarely used BSM
vertices; many improvements were made to general decayers, allowing
four-body decays in BSM for the first time; Powheg is enabled in
General two-body decayers; and the handling of colour
sextets has been improved.
** A new HiggsPair matrix element in Contrib.
** A new matrix element for single top production.
** The Higgs mass is now set to 125.9 GeV (from PDG 2013 update).
** C++-11 testing
To help with the coming transition to C++-11, we provide the new
--enable-stdcxx11 configure flag. Please try to test builds with
this flag enabled and let us know any problems, but do not use this
in production code yet. In future releases, this flag will be on by
default.
** Other changes
*** Many new Rivet analyses have been included in the Tests directory.
*** Cleaned Shower header structure; grouped shower parameters into one struct.
*** The boolean Powheg flag in HwMEBase changed to an enumeration.
* Herwig++-2.6.3 release: 2013-02-22
** Decay vertex positioning in HepMC output
Pseudo-vertices that Herwig++ inserts for technical reasons will
now not contribute to the Lorentz positions of downstream vertices.
Thanks to ATLAS for the bug report!
** Updated Rivet tests
Herwig's library of Rivet test runs has been brought up-to-date
with new analyses that were recently published by the Rivet
collaboration.
* Herwig++-2.6.2 release: 2013-01-30
** Fixes for PDF and scale choices in POWHEG events
Scale settings for MPI and the regular shower are now correct in
POWHEG events. This should fix reported anomalies in POWHEG jet rates.
NLO PDFs are now also set consistently in the example input files.
** Ticket #373: Branching ratio factors in cross-section
If any decay modes are selectively disabled, setting the following
post-handler will cause all reported cross-sections to include the
branching ratio factor(s) from the previous stages correctly:
create Herwig::BranchingRatioReweighter BRreweight
insert LHCGenerator:EventHandler:PostDecayHandlers 0 BRreweight
** Anomalous vertices now possible in MEfftoVH
** Interactive shell does not quit on error
** Better warning messages for events from inconsistent LHEF files
** Possible division by zero error fixed in BSM branching ratio calculations
** Decayer and ME changes to improve checkpointing
The checkpointing changes in ThePEG 1.8.2 are implemented here, too. Regular
dump files are consistent now.
* Herwig++-2.6.1 release: 2012-10-16
** Configure switches
The various switches to turn off compilation of BSM models have
been unified into a single '--disable-models'. A new flag
'--disable-dipole' can be used to turn off the compilation of the
Dipole and Matchbox codes.
** Ticket #348: Search path for repository 'read' command
The search path for the 'read' command is configurable on the
command line with the -i and -I switches. By default, the
installation location is now included in the search path, so that
'Herwig++ read LEP.in' will work in an empty directory. The current
working directory will always be searched first.
The rarely used "Herwig++ init" command has been made consistent
with 'read' and 'run' and should now be used without the '-i' flag.
** Width treatment in BSM
The width treatment in BSM decay chains has been greatly improved
and is now switched on by default in the .model files. To get the
old behaviour, use
set /Herwig/NewPhysics/NewModel:WhichOffshell Selected
** New BSM models
Little Higgs models with and without T-parity are now available.
** Resonance photon lifetime
A lifetime bug affecting decays of pi0 to e+e-X was fixed. The
virtual photon is not part of the event record anymore.
** Ticket #371: Hard diffraction FPE
Herwig++ 2.6.0 introduced a bug into the diffraction code which
would abort any runs. This is now fixed.
** O2AlphaS
Support for setting quark masses different from the particle data
objects as introduced in ThePEG 1.8.1 has been enabled.
** Matchbox
Several improvements and bug fixes are included for
Matchbox. Amplitudes relevant to pp -> Z+jet and crossed processes
at NLO are now available, and various scale choices have been added
in a more flexible way. All subtraction dipoles for massive quarks
are now included.
** Dipole shower
Parameters to perform scale variations in the shower have been
added to estimate uncertainties. A bug in showering off gg -> h has
been fixed.
** Minor fixes
*** Two broken colour structures in GeneralHardME
*** Susy Higgs mixing matrix
*** BaryonFactorizedDecayer out-of-bounds access
*** Mass values in SimpleLHCAnalysis
* Herwig++-2.6.0 release: 2012-05-21 (tagged at SVN r7407)
** New NLO framework
Matchbox, a flexible and very general framework for performing NLO
calculations at fixed order or matched to parton showers is
provided with this release.
** Dipole shower algorithm
A first implementation of the coherent dipole shower algorithm by
Plätzer and Gieseke (arXiv:0909.5593 and arXiv:1109.6256) is
available.
** Alternative samplers and the ExSample library
The ExSample library by Plätzer (arXiv:1108.6182) is shipped along
with Herwig++ in an extended version. The extended version provides
SamplerBase objects which can be used alternatively to the default
ACDCSampler.
** New BSM models
*** New colour sextet diquark model
A colour sextet diquark model has been included, as described in
Richardson and Winn (arXiv:1108.6154).
*** Models reproducing the CDF t-tbar asymmetry
Four models that can reproduce the reported t-tbar asymmetry have
been included.
*** Zprime
A simple standard model extension by one additional heavy neutral
vector boson.
** Interface to AlpGen, with MLM merging
The Contrib directory contains a new interface to the AlpGen matrix
element generator. AlpGen events must be preprocessed with the
provided AlpGenToLH.exe tool before they can be used. More
information can be found in the Herwig++ 2.6 release note.
** HiggsVBF Powheg
Higgs boson production by vector boson fusion is available at NLO
in the POWHEG scheme, as described in d'Errico, Richardson
(arXiv:1106.2983). The Powheg DIS processes were available in
Herwig++-2.5.2 already.
** Statistical colour reconnection
Alternative mechanisms to minimize the colour length Sum(m_clu)
before the hadronization stage, based on Metropolis and annealing
algorithms.
** Energy extrapolation of underlying-event tunes
To describe underlying-event data at different c.m. energies, the
energy-dependent parameter pT_min will now be adjusted
automatically, following a power-law. The new tune parameters are
the value at 7000 GeV "MPIHandler:pTmin0", and MPIHandler:Power.
** Ticket #239: Reporting of minimum-bias cross-section
When simulating minimum-bias events using the MEMinBias matrix
element, the correct unitarized cross section can now be reported
via the standard facilities; it is no longer necessary to extract
it from the .log file of the run. The corresponding functionality
is enabled by inserting a MPIXSecReweighter object as a
post-subprocess handler:
create Herwig::MPIXSecReweighter MPIXSecReweighter
insert LHCHandler:PostSubProcessHandlers 0 MPIXSecReweighter
** Dependency on 'boost'
Herwig++ now requires the boost headers to build; if not detected
in standard locations, specify with the --with-boost configure
option.
** Tests directory
The Tests directory now contains input cards for almost all Rivet
analyses. A full comparison run can be initiated with 'make tests'.
** Minor changes
*** Default LHC energy now 8 TeV
All LHC-based defaults have now been updated to use 8 TeV as the
center-of-mass energy.
*** Herwig::ExtraParticleID -> ThePEG::ParticleID
The namespace for additional particles has been unified into
ThePEG::ParticleID
*** MEee2VectorMeson
The e+e- -> vector meson matrix element has moved from Contrib into
HwMELepton.so
*** SUSY numerics fixes
Better handling of rare numerical instabilities.
*** YODA output for Rivet
The built-in histogramming handler can now output data in the YODA
format used by Rivet.
*** Consistency checks in SLHA file reader
Better warnings for inconsistent SusyLHA files
*** better colour flow checking for development
** Bug fixes
*** Extremely offshell W from top decay
Numerical improvements for very off-shell W bosons coming from top
decays.
*** Ticket #367: problems in using SUSY + LHE
Susy events from Les Houches event files are now handled better.
*** Infinite loop in remnant decayer
The remnant decayer will now abort after 100 tries.
*** Fix to HiggsVBF LO diagrams
The diagram structure of HiggsVBF LO matrix elements has been fixed.
*** LEP thrust fix
The calculation of the transverse momentum of a branching from the
evolution variable in final-state radiation can now be
changed. While formally a sub-leading choice this enables a better
description of the thrust distribution in e+e- collisions at
small values of the thrust. Currently the default behaviour, where
the cut-off masses are used in the calculation, remains the same
as previous versions.
* Herwig++-2.5.2 release: 2011-11-01 (tagged at SVN r6928)
** Optional new jet vetoing model
The jet vetoing model by Schofield and Seymour (arXiv:1103.4811) is
available via Evolver:ColourEvolutionMethod,
PartnerFinder:PartnerMethod and SplittingFunction:SplittingColourMethod.
The default behaviour is unchanged.
** MPI tune
Version 3 of the MPI tunes is now the default. Please note that the
pT parameter is energy-dependent and needs to be modified when an
LHC run is not at 7 TeV.
The latest tunes are always available at
http://projects.hepforge.org/herwig/trac/wiki/MB_UE_tunes
** MPI PDFs
MPI PDFs can now be controlled independently.
** Initialization time speedup
A new BSMModel base class was introduced between StandardModel and
the BSM model classes. Together with a restructured decay mode
initialization, this offers significantly faster startup times for
BSM runs. ThreeBodyDecays can now always be switched on without a
large speed penalty.
** Decay mode file
Decay mode files in the SLHA format can now be read separately in
any BSM model with 'set Model:DecayFileName filename'
** Powheg DIS
Charged- and neutral-current DIS processes implementing the POWHEG
method are now available.
** Diffraction models
Xi cut implemented in PomeronFlux
** Ticket #352: Colour reconnection fixed in DIS
** Ticket #353: Improved numerical stability in chargino decays
** Ticket #358: Infinite loop in top events with pT cut in shower
** Ticket #361: Problem with duplicate 2-body modes in BSM
** Tickets #362 / #363: Crashes with baryon number violating models
Particle decays in SUSY models with RPV now work correctly in the
colour 8 -> 3,3,3 case. Colour reshuffling now works for RPV
clusters.
** Improved Fastjet detection
The configure step uses fastjet-config to make sure all header file
paths are seen.
** Darwin 11 / OS X Lion
A configure bug was fixed which prevented 'make check' from
succeeding on OS X Lion.
** Vertex classes
The specification of QED / QCD orders has been moved to the vertex
constructors, to allow ThePEG consistency checks. WWHH vertices in
MSSM and NMSSM were fixed. Some Leptoquark and UED vertices fixed.
** Hadronization
Cleanup of obsolete code.
* Herwig++-2.5.1 release: 2011-06-24 (tagged at SVN r6609)
** Example input files at 7 TeV
All our example input files for LHC now have their beam energy set
to 7 TeV instead of 14 TeV.
** Colour reconnection on by default
The colour reconnection tunes are now the default setup. Version 2
of the tunes replaces the *-1 tunes, which had a problem with LEP
event shapes.
** Run name tags
Aded possibility to add a tag to the run name when running with the
'-t' option. One run file can thus be run with different seeds and
results stored in different output files.
** Floating point exceptions
The new command line option -D enables floating point error checking.
** General improvements to WeakCurrent decays
** Remnant decayer
Hardwired gluon mass was removed.
** WeakCurrentDecayConstructor
Instead of specifying separate Particle1...Particle5 vectors for
the decay modes, the new interface DecayModes can be filled with
decay tags in the standard syntax.
** BSM: improvements to handling of vertex and model initialisation
** Powheg Higgs
Option to use pT or mT as the scale in alphaS and for the
factorization scale in the PDFs
** Ticket #337: Tau polarization wrong in charged Higgs decay
** Ticket #339: Colour flows in GeneralThreeBody Decayers for 3bar -> 8 3bar 1
** Ticket #340: Crash for resonant zero-width particles
** Ticket #341: Varying scale for BSM processes
The scale used is now ResonantProcessConstructor:ScaleFactor or
TwoToTwoProcessConstructor:ScaleFactor multiplied by sHat.
** Ticket #346: Chargino decays
Chargino decayers now automatically switch between the mesonic
decays for mass differences less than 2 GeV and the normal partonic
decays above 2 GeV.
** Ticket #349: Stop by default on input file errors
The '--exitonerror' flag is now the default behaviour for the
Herwig++ binary. To switch back to the old behaviour,
'--noexitonerror' is required.
** Ticket #351: Four-body stop decays
** Tested with gcc-4.6
* Herwig++-2.5.0 release: 2011-02-08 (tagged at SVN r6274)
** Uses ThePEG-1.7.0
Herwig++ 2.5.0 requires ThePEG 1.7.0 to benefit from various
improvements, particularly: handling of diffractive processes;
respecting LD_LIBRARY_PATH when loading dynamic libraries,
including LHAPDF; improvements to repository commands for decay
modes. See ThePEG's NEWS file for more details.
** POWHEG improvements
*** New POWHEG processes
Simulation at NLO accuracy using the POWHEG method is now
available for hadronic diboson production (pp to WW,WZ,ZZ), Higgs
decays to heavy quarks, and e+e- to two jets or ttbar, including
full mass dependence.
*** Input file changes
The input files for setting up POWHEG process simulation have been
simplified. See the example files LHC-Powheg.in and TVT-Powheg.in
for the improved command list.
*** Structural changes
The POWHEG backend in the shower code has been restructured to
make future additions easier: PowhegEvolver has merged with
Evolver; both the matrix element corrections and real corrections
in the POWHEG scheme are implemented directly in the ME or Decayer
classes.
** New processes at leading order
*** Photon initiated processes
We have added a matrix element for dijet production in gamma
hadron collisions.
*** Bottom and charm in heavy quark ME
The option of bottom and charm quarks is now supported for heavy
quark production in MEHeavyQuark.
** Colour reconnection
The cluster hadronization model has been extended by an option to
reconnect coloured constituents between clusters with a given
probability. This new model is different from the colour
reconnection model used in FORTRAN HERWIG, and improves the
description of minimum bias and underlying event data.
** Diffractive Processes
Both single and double diffractive processes are now supported in
Herwig++. The Pomeron PDF is implemented using a fit to HERA data,
and a pion PDF can be used to model reggeon flux.
** BSM physics
*** New models
We have added new BSM models, particularly ADD-type extra
dimension models and the next-to-minimal supersymmetric standard
model (NMSSM). Effects of leptoquarks can as well be simulated.
*** Vertex additions
We have added flavour changing stop interactions (stop -
neutralino - charm) and gravitino interactions with particular
emphasis on numerical stability for very light gravitinos.
Tri-linear Higgs and Higgs-Higgs/Vector-Vector four-vertices are
available as well.
*** Input file changes
The SUSY model can now also extract the SLHA information from the
header of a Les Houches event file: replace the SLHA file name
in the example input files with the LH file name.
*** Structure
The backend structure of the HardProcessConstructor has changed,
to allow easier inclusion of new process constructors. Some 2->3
BSM scattering processes involving neutral higgs bosons are now
included. The spin handling has been improved in the background.
** Shower splitting code reorganized
The selection of spin structures has been decoupled from the choice
of colour structure. This gives more flexibility in implementing
new splittings. Selected splittings can be disabled in the input
files.
** B mixing
B mixing, and indirect CP violation in the B meson system are
included now.
** Looptools
The Looptools directory has been updated to reflect T.Hahn's
Looptools 2.6.
** Contrib changes
The ROOT interface has been removed as deprecated. The MCPWNLO code
has temporarily been removed from the Contrib directory as a major
review of this code is required. Additionally, there are various
fixes to all other codes shipped in Contrib.
** DIS improvements
The momentum reshuffling in DIS events has been improved.
** mu and nu beams
mu, nu_e and nu_mu and their antiparticles are now available as
beam particles. They are all supported in the DIS matrix
elements. mu+ mu- collisions are supported in the general
matrix element code for BSM models, but not yet in the hard-coded
matrix elements for lepton-lepton scattering.
** Structural changes
*** Inline code
Inline code has been merged into the header files, .icc files were
removed.
*** Silent build
By default, Herwig++ now builds with silent build rules. To get
the old behaviour, run 'make V=1'.
*** Debug level
The debug level on the command line will now always have priority.
*** Event counter
The event counter has been simplified.
*** Interpolator persistency
Interpolators can now be written persistently.
** Ticket #307: Momentum violation check in BasicConsistency
Added parameters AbsoluteMomentumTolerance and
RelativeMomentumTolerance
** Example POWHEG input files
The example input files for Powheg processes now set the NLO
alpha_S correctly, and are run as part of 'make check'.
** Truncated shower
A problem which lead to the truncated shower not being applied in
some cases has been fixed.
** Fixes to numerical problems
Minor problems with values close to zero were fixed in several
locations.
** Remove duplicated calculation of event shapes
An accidental duplication in the calculation of event shapes was
removed, they are now only calculated once per event. Several other
minor issues in the event shape calculations have also been fixed.
** MRST PDFs fixed
An initialization problem in the internal MRST PDFs was fixed.
** Vertex scale choice
The scale in the Vertex classes can now be zero where
possible.
** Treatment of -N flag
The Herwig++ main program now correctly treats the -N flag
as optional.
** Numerical stability improved
The numerical stability in the 'RunningMass' and
'QTildeReconstructor' classes has been improved. The
stability of the boosts in the SOPTHY code for the