From torbjorn at thep.lu.se Sat Apr 10 12:14:03 2021 From: torbjorn at thep.lu.se (=?UTF-8?Q?Torbj=c3=b6rn_Sj=c3=b6strand?=) Date: Sat, 10 Apr 2021 13:14:03 +0200 Subject: [Pythia8-announce] Pythia 8.304 now available Message-ID: ===================================================================== Dear All, PYTHIA 8.304 has been released today, and can be downloaded from http://home.thep.lu.se/Pythia as usual. The main news is a significantly updated version of the Vincia shower framework. There is also a sprinkling of other news, and the traditional set of bug fixes. We remind that Pythia 8.3 is to be considered the main branch. As for 8.303, however, some recent matching-and-merging fixes in 8.245 still have to find their way into 8.3. You find a summary of changes below, based on the list in the Update History, found e.g. in the html manual. It starts with the major new features and then proceeds towards smaller news and bug fixes. Wishing you an enjoyable experience with PYTHIA 8.304. Sincerely yours, The Pythia 8 Collaboration (Christian Bierlich, Nishita Desai, Leif Gellersen, Ilkka Helenius, Philip Ilten, Leif L?nnblad, Stephen Mrenna, Stefan Prestel, Christian Preuss, Torbj?rn Sj?strand, Peter Skands, Marius Utheim, Rob Verheyen) -------------------------------------------------------------------- P.S. Recently we acquired the pythia.org domain name. In a not-too-distant future the Pythia webpages will be moved there. Already now, however, the authors at pythia.org address should always be used when contacting the authors, as it allows us to coordinate replies. You may also include the individual addresses of authors that are relevant for a specific issue. Never contact several persons independently on the same topic, thereby potentially leading to double work. Abuse will have consequences. When responding to emails from us at authors at pythia.org, reply directly to the email, which has a unique return address of the form incoming+@incoming.gitlab.com, and not authors at pythia.org. Please consider allowing your correspondence to be made publicly available to other users via our issue tracker, by replying at any point with your express permission, e.g. "this correspondence can be made public". ===================================================================== Summary list of changes, starting with the major physics news and then proceeding towards bug fixes: * Christian Preuss and Rob Verheyen join the author team, and Christine Rasmussen leaves it. * Significant updates to the Vincia shower implementation. - New "sector" antenna showers implemented and made default. - Minor changes to a few of the default Vincia hadronisation parameters, reflecting the new sector shower default. - New dedicated LO merging scheme for the sector antenna showers. The scheme is similar to CKKW-L in spirit, but exploits the bijective nature of the sector shower to vastly reduce the number of histories that need to be taken into account. - New full-fledged electroweak shower option implemented. The splitting kernels are based on collinear limits of corresponding helicity matrix elements, so this EW shower model requires Born partons with assigned helicities. Currently these must either be input via LHEF or (for experts) runtime via Vincia's interface to MG5 matrix elements. - Introduced tools to automatically generate MadGraph plugin libraries. - New options for interleaved resonance decays implemented and made default. * Interleaved resonance decays are also introduced for the standard simple showers, but is not made default there. * Revised internal handling of shower variations and splitting enhancements, both for regular and trial emissions. Enhancements of rare shower splittings are now steered by settings instead of UserHooks, and the necessary weights are automatically included in the shower and merging weights. * A number of updates have been made to sophisticated tau decays. - External SPINUP is now always interpreted as a helicity state in the lab frame to ensure consistent treatment between tau decays and helicity showers. - The default external mode for tau decays has been changed to handle helicity showers. - gamma gamma -> tau^+ tau^- processes are now handled. - Helicity states for initial beams can be specified and used in tau decays. * Added HDF5 support. * Added support for lepton-photon initiated hard processes generated internally or externally. Thanks to Liu Yao-Bei. * Minor code changes to allow hadronic rescattering in nuclear collisions (remove limit on number of rescatterings, increase maximum transverse vertex location). * Double quarkonia production, if enabled, is now also included in both MPI and second hard processes. * Added some new functionality to the Hist class. * Moved the event information in the Info class to an appropriate diffractive system for hard diffraction. This way also the hard-process scale is properly propagated for primordial kT sampling. * The stopMassNow in StringFragmentation.cc is made to increase faster for charm and bottom end quarks, to allow an increased few-body fraction further above threshold. Thanks to Andy Buckley. * Added ResonanceDecayFilterHook and example main103.cc to demonstrate how to select specific final states from resonance decays. * Fixed vertex smearing in heavy ion events. * Fixed remnant handling for e+e- collisions for photon-initiated processes, thanks to Murat K?ksal. * Minor fixes in xml/html QCD process links and text. * Several small bug fixes based on error reports by Vittorio Zecca. - Fixed a bug where some elastic cross sections for pi K at low energies were set equal to the total ones. - Protect against too high constituent masses inside a hadron in LowEnergyProcess.cc, already at an earlier stage of the process. - Protect against exp(-infinity) in HadronLevel.cc. - Two fixes for first step in the trial emissions in StringFragmentation.cc, used primarily in the thermal model option. - Properly set the photon-in-lepton PDF to vanish at very large x, rather than give unphysical values there. - Better protection against weird results for the rap and eta methods in Basics.h, and y in Event.cc. - Fixed pointer logic in Dire getXPDF. - Migrated from log(1 + x) to log1p(x) for numerical stability. * Several small fixes in response to a static code analysis, provided by Dmitri Konstantinov. - Fix inconsistency in the usage of the third argument of the dsigmaEl method in the classes derived from SigmaTotAux. - Flawed and unused LowEnergySigma::sigmaPartial method removed. - Fix inconsistent type for varWidthIn in ParticleDataEntry class. - Introduce minor changes, e.g. to protect against out-of-bounds addressing or insert missing initializer, even though there is no evidence that it is needed. - Small speedup of the Vec4 [] operator using switch() instead of if to find element to be returned. - Several (mostly minor) optimisations in Vincia. * Bug fixed in the new possibility to let particles with narrow widths (such as onia states) obtain a simple Breit-Wigner distribution, specifically for MPIs, introduced in 8.240. This bug led to excessive rejection of low-invariant-mass interactions. Thanks to Albert De Roeck. * Default event record checks switched off for main21.cc, to avoid issues with junction mother-daughter relations not being fully set. Also change so that showers are not called twice. Now all available cases are looped over, but easy to change back to study only one. ===================================================================== From torbjorn at thep.lu.se Mon May 3 20:03:49 2021 From: torbjorn at thep.lu.se (=?UTF-8?Q?Torbj=c3=b6rn_Sj=c3=b6strand?=) Date: Mon, 3 May 2021 21:03:49 +0200 Subject: [Pythia8-announce] Pythia 8.305 now available Message-ID: <4244f71a-8b3a-9041-36db-0a92d33f298b@thep.lu.se> ===================================================================== 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 L?nnblad, Stephen Mrenna, Stefan Prestel, Christian Preuss, Torbj?rn Sj?strand, Peter Skands, Marius Utheim, Rob Verheyen) -------------------------------------------------------------------- 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. As already mentioned, already now the new the authors at pythia.org address should always be used when contacting the authors, as it allows us to coordinate replies. You may also include the individual addresses of authors that are relevant for a specific issue. Never contact several persons independently on the same topic, thereby potentially leading to double work. Abuse will have consequences. When responding to emails from us at authors at pythia.org, reply directly to the email, which has a unique return address of the form incoming+@incoming.gitlab.com, and not authors at pythia.org. Please consider allowing your correspondence to be made publicly available to other users via our issue tracker, by replying at any point with your express permission, e.g. "this correspondence can be made public". ===================================================================== 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. ===================================================================== From peter.skands at monash.edu Sat Jun 5 07:54:53 2021 From: peter.skands at monash.edu (Peter Skands) Date: Sat, 5 Jun 2021 16:54:53 +1000 Subject: [Pythia8-announce] Pythia 8 News and Announcements In-Reply-To: References: Message-ID: <073d307e-dd7b-4431-8ee4-6d587f659831@Spark> ===================================================================== Dear All, This announcement is to let you know that the PYTHIA web pages have moved to: ??pythia.org There is also a new?PYTHIA contact email, ? authors at pythia.org which should always be used when contacting (any of) us about PYTHIA, as it allows us to coordinate replies. See further details about this below. For the foreseeable future, the old site at?http://home.thep.lu.se/~torbjorn/Pythia.html?will continue to contain a link and forward to the new web page, but now would be a good time to update relevant bookmarks and/or web page links to point to the new site and/or email list. The organisation of the PYTHIA project is also changing, to accommodate the growing size of the project and to allow in particular Torbj?rn to focus a bit more on research and a bit less on administrative tasks in PYTHIA. Thus, the administration of PYTHIA will in the future be shared by a triumvirate consisting of a spokesperson (and deputy), a codemaster, and a webmaster. The people currently elected to fill these roles are: ? Spokesperson: Peter Skands ? Deputy Spokesperson: Ilkka Helenius. ? Codemaster: Phillip Ilten. ? Webmaster: Christian Bierlich. In addition, Torbj?rn Sj?strand will remain Adjoint Spokesperson for life. Finally, we are very happy to congratulate Torbj?rn Sj?strand and Bryan Webber on being awarded the 2021 EPS High Energy and Particle Physics prize, "for the conception, development and realisation of parton shower Monte Carlo simulations, yielding an accurate description of particle collisions in terms of quantum chromodynamics and electroweak interactions, and thereby enabling the experimental validation of the Standard Model, particle discoveries and searches for new physics." -------------------------------------------------------------------- Further details on how to use authors at pythia.org: As already mentioned, this should always be used when contacting any of the PYTHIA authors, as it allows us to coordinate replies. You may also include the individual addresses of authors that are relevant for a specific issue. Never contact several persons independently on the same topic, thereby potentially leading to double work. Abuse will have consequences. When responding to emails from us at authors at pythia.org, please reply directly to the email you receive, which has a unique return address of the form incoming+@incoming.gitlab.com, and not authors at pythia.org. Please consider allowing your correspondence to be made publicly available to other users via our issue tracker, by replying at any point with your express permission, e.g. "this correspondence can be made public". -------------------------------------------------------------------- Wishing you an enjoyable experience with PYTHIA. Sincerely yours, The Pythia 8 Collaboration (Christian Bierlich, Nishita Desai, Leif Gellersen, Ilkka Helenius, Philip Ilten, Leif L?nnblad, Stephen Mrenna, Stefan Prestel, Christian Preuss, Torbj?rn Sj?strand, Peter Skands, Marius Utheim, Rob Verheyen) ===================================================================== -------------- next part -------------- An HTML attachment was scrubbed... URL: From peter.skands at monash.edu Wed Jun 30 12:20:03 2021 From: peter.skands at monash.edu (Peter Skands) Date: Wed, 30 Jun 2021 21:20:03 +1000 Subject: [Pythia8-announce] Pythia 8.306 now available In-Reply-To: <60ad0b42-949f-4c3d-8e51-3fe36c866942@Spark> References: <60ad0b42-949f-4c3d-8e51-3fe36c866942@Spark> Message-ID: <457bc0bc-0a35-4591-8045-7f24e6e07fea@Spark> ===================================================================== Dear All, PYTHIA 8.306 has been released today, and can be downloaded from ? http://pythia.org Note that this is the first release to the new Pythia.org webpage. This is an "unscheduled" bug fix update, prompted by a showstopper bug in Powheg matching code, but a few other minor fixes are included also. A brief summary is included below and in the Update History part of the HTML manual. Wishing you an enjoyable experience with PYTHIA 8.306. Sincerely yours, The Pythia 8 Collaboration (Christian Bierlich, Nishita Desai, Leif Gellersen, Ilkka Helenius, Philip Ilten, Leif L?nnblad, Stephen Mrenna, Stefan Prestel, Christian Preuss, Torbj?rn Sj?strand, Peter Skands, Marius Utheim, Rob Verheyen) -------------------------------------------------------------------- CONTACT: if you need to contact any of the authors, please use the new authors at pythia.org address, as it allows us to coordinate replies. You may also include the individual addresses of authors that are relevant for a specific issue. Never contact several persons independently on the same topic, thereby potentially leading to double work. Abuse will have consequences. When responding to emails from us at authors at pythia.org, reply directly to the email, which has a unique return address of the form incoming+@incoming.gitlab.com, and _not_ authors at pythia.org. Please consider allowing your correspondence to be made publicly available to other users via our issue tracker, by replying at any point with your express permission, e.g. "this correspondence can be made??public". ===================================================================== Summary list of changes for 8.306. ? Fixed incorrect scale being set when applying the POWHEG veto (e.g., main31.cc). Note that the number of emissions is correct in 8.303, but is incorrect in 8.304 and 8.305. Thanks to Mikhail Kirsanov. ? Fixed repeated initialization causing an ever expanding physics pointer list in the main Pythia class. ? Fixed issue for HepMC output from Vincia, which would previously issue warnings about inconsistent mother/daughter relationships, caused by Vincia's antenna-style bookkeeping by which emitted partons have two mothers instead of one. Minor modifications to Vincia's QCD shower to ensure that the first mother is the one that changed colour and hence would be identified with the "radiator" in a collinear context. Analogous modifications for QED so the most collinear parent is the first mother. ? Removed assert statements from Angantyr. ? Shortened Pythia constructor header. ===================================================================== -------------- next part -------------- An HTML attachment was scrubbed... URL: