[Pythia8-announce] Pythia 8.183 now available

[Torbjorn Sjostrand]

Dear All,

Pythia 8.183 has now been released, and can be downloaded from

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

Some of the main changes are summarized below. For a more
extensive listing, see the "Update History" in the online
html/php manual. Most changes will not affect the normal user.

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)

MAIN NEWS

* A potentially severe bug has been found in version 8.180:
   by mistake the SpaceShower:vetoWeakJets, SpaceShower:dopTDampMass
   and TimeShower:dopTDampMass were given a default on value rather
   than off. This reduces the emission of two or more hard jets
   for processes 221 and 222, i.e. gamma^*/Z^0/W^+- production.
   It thereby also softens the pT spectrum of the gauge boson.
   Other processes should be unaffected.

* The emission of W and Z weak gauge bosons in ISR and FSR parton
   showers now is fully implemented (but off by default), see
   "Weak Gauge Boson Radiation in Parton Showers",
   by J.R. Christiansen and T. Sjöstrand,
   LU TP 14-02, MCnet-14-01, arXiv:1401.5238 [hep-ph]

* The worksheet, intended to help beginners get going, has been
   updated and expanded. Notably with new exercises on CKKW-L merging
   and Higgs production and decay.

* Several new tunes, most notably the Monash 2013 one, which may
   become the new default in the future. Therefore feedback on it
   is particularly appreciated.

* The LO PDF sets in the NNPDF2.3 QCD+QED family now are valid down
   to Q^2 = 1 GeV^2 and x = 10^-9.

* Some moderate improvements in the merging machinery.

* Changed status code for partons in the hardest interaction of
   the SoftQCD processes, from the 30'ies to the 20'ies range.

* The internal PYTHIA partial widths of the SM Higgs now by
   default are rescaled to the values recommended by the LHCXSWG.

* New possibility to pick fixed factorization scale for ISR (&FSR).

* Some cleanup of code and documentation files, and minor fixes.