[Pythia8-announce] Pythia 8.180 now available

[Torbjorn Sjostrand]

Dear All,

Pythia 8.180 has now been released, and can be downloaded from

http://home.thep.lu.se/~torbjorn/Pythia.html

Some of the main features are summarized in the following two
sections, on physics news and on other changes. For a more
extensive listing, see the "Update History" in the online
html/php manual. Most changes will not affect the normal user,
the key exception being the move of header files from the
include subdirectory to include/Pythia8.

A sincere thank to all the persons who have contributed with
new code, bug reports or suggestions for improvements.

As always, we look forward to constructive feedback.

Sincerely yours,
The Pythia 8 Collaboration
(Torbjörn Sjöstrand, Jesper Roy Christiansen, Nishita Desai,
Philip Ilten, Stephen Mrenna, Stefan Prestel, Peter Skands)

PHYSICS NEWS

* Four PDF sets have been added from the NNPDF2.3 QCD+QED family:
   the central sets for LO with alpha_s(M_Z) = 0.130 and 0.119,
   NLO with alpha_s(M_Z) = 0.119, and NNLO with alpha_s(M_Z) = 0.119.

* The fjcore version 3.0.5 code from FastJet has been included with
   the PYTHIA distribution. SlowJet now by default becomes a front end
   to fjcore, but the old native behaviour is retained as an option.

* The merging code has been updated, with corrected handling of
   massive partons. The bookkeeping for the hard process has been
   upgraded to accommodate more general BSM processes. The
   treatment of incomplete histories has been upgraded.

* Added previously missing SUSY processes for associated production
   of a gluino with a neutralino or chargino, and for direct slepton
   production. Generalized the cross section formulae for
   squark + gluino and gluino + gluino to the case of non-minimal
   flavour violation. Some other SUSY changes, for couplings, SLHA2
   support, off-shell decays, decay lengths, and more.

* Modified the contact interaction term normalization of the
   f fbar -> l lbar process to agree with the one used in PYTHIA 6.

* The global recoil option for final-state showers has been extended
   to improve possibility for matching to other programs.

* Allow six-flavour running of alpha_s above the top threshold,
   and implement option with CMW rescaling of the Lambda values.

* Further extensions of the weak-showering machinery, but still
   experimental.

* Allow resonances to decay before or after colour reconnection.

OTHER ISSUES

* Nishita Desai joins as new author.

* All the header files include/*.h have been moved to
   include/Pythia8/*.h to better comply with conventions
   in other libraries. NOTE: not backwards compatible.

* Class, file and subdirectory names for converting PYTHIA events
   to the HepMC format are renamed to Pythia8ToHepMC and similar
   to avoid potential name clashes. NOTE: not backwards compatible.

* The configure/Makefile step has been extended such that a
   bin/pythia8-config script is constructed, to simplify linking
   to other libraries.

* The "minbias" event class and (SoftQCD) flag has been renamed to
   "nondiffractive". (For now SoftQCD:minbias remains as alias.)

* Allow the Les Houches lifetime information optionally to be
   replaced by the standard PYTHIA selection procedure.

* Two new vectors of integers SUSY:idVecA and SUSY:idVecB have been
   introduced to allow a more flexible selection of final states
   in SUSY processes.

* Introduced a copy constructor for the Event class.

* The mass() methods, for particle-by-particle selection, are
   renamed mSel() to avoid confusion with m().

* MVec and PVec standardized as vectors of modes and parameters
   (vectors of integers and double-precision numbers).

* An illustration how to force specific Higgs branching ratios
   is now found in main16.cmnd.

* A new main46.cc illustrates how to write a ProMC file with PYTHIA
   events.

* The main85.cc - main88.cc have obtained support for zipped LHEFs.

* Remove obsolete main91.cc and associated Makefile code.

* Catch cases where junction topologies are sent to the ministring
   machinery, which is not set up to handle it.

* Fixed several bugs, some physics-driven, others including
   division by zero and addressing arrays out of bounds, and
   constructions giving compiler warnings.