[Pythia8-announce] Pythia 8.305 now available

[Torbjörn Sjöstrand]

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Dear All,

PYTHIA 8.305 has been released today, and can be downloaded from
       http://home.thep.lu.se/Pythia
as usual.

This is an "unscheduled" bug fix update, prompted by a showstopper
bug in the Dire code, but includes also some other fixes.

Wishing you an enjoyable experience with PYTHIA 8.305.

Sincerely yours,
The Pythia 8 Collaboration
(Christian Bierlich, Nishita Desai, Leif Gellersen, Ilkka Helenius,
Philip Ilten, Leif Lönnblad, Stephen Mrenna, Stefan Prestel,
Christian Preuss, Torbjörn Sjöstrand, Peter Skands, Marius Utheim,
Rob Verheyen)

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P.S. This is going to be the last release to the current webpage.
A new pythia.org webpage is in preparation and will soon take over.
The current webpage will then be removed.

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Summary list of changes.

* Fixed an issue that otherwise caused the weights of the Dire
   parton shower to be erroneously discarded. The fix will impact
   the results produced with the Dire parton shower model. The
   results of the previous version should be considered incorrect.

* Fixed potential for segfault in Weights.cc if
   weightsShowerPtr == nullptr.

* A number of fixes related to Vincia.
   - Bug fixes in Vincia's merging, addressing the issue that
     occasionally incomplete histories were accepted while a complete
     one was available.
   - Fixed some small bugs in Vincia's QED shower that could cause
     issues when running at very high energies.
   - Minor namespace fixes. Moved "using namespace VinciaConstants"
     from headers to source files and moved "enum antFunType" inside
     the Pythia8 namespace.
   - Added default initialisers for data members in several Vincia
     classes, to avoid potentially undefined behaviour. Thanks to
     V. Zecca.

* Fixed unintentional initial-state radiation from unresolved hadron
   beams, when set with option BeamRemnants:unresolvedHadron, which
   would break up the beam. Minor fix also for cases where two
   unresolved hadrons.

* Added threshold check on low energy cross sections. This fixes a
   small bug reported by V. Zecca.

* Corrected bug in normalization of histograms in main07.cc.
   Thanks to M. Baker and A. Thamm.

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