<chapter name="Front"> 
 
<h1>PYTHIA 8</h1> 
 
<h3>Welcome to PYTHIA - The Lund Monte Carlo!</h3> 
 
<p/> 
PYTHIA is a general-purpose event generator for high-energy particle 
collisions. PYTHIA 8 is the successor to PYTHIA 6, rewritten from 
scratch in C++. It includes many new features, but rests on the same 
historical physics base, including concepts such as soft and hard 
processes, parton showers, multiparton interactions and string 
fragmentation. With the current PYTHIA 8.3 version the step has been 
taken from <code>C++98</code> to <code>C++11</code>, but the 
transition from 8.2 should largely be transparent to users. Also 
several new physics features are made available. 
 
<h3>Documentation</h3> 
 
On these webpages you will find the manual for PYTHIA 8.3. The physics 
descriptions may in places still need to be updated, but the 
documentation of available settings and other practical details should 
be fully up-to-date. Use the left-hand index to navigate this 
documentation of program elements, especially of all possible program 
settings. All parameters are provided with sensible default values, 
however, so you need only change those of relevance to your particular 
study, such as choice of beams, processes and phase space cuts. The 
pages also contain a fairly extensive survey of all methods available 
to the user, e.g. to study the produced events. What is lacking on 
these webpages is an overview, on the one hand, and an in-depth 
physics description, on the other. 
 
<p/> 
The overview can be found in the attached PDF file 
<br/><a href="../pdfdoc/pythia8200.pdf" target="page"> 
<b>An Introduction to PYTHIA 8.2</b></a> 
<br/>T. Sj&ouml;strand et al, Comput. Phys.Commun. 191 (2015) 159 
[arXiv:1410.3012 [hep-ph]]. 
<br/>You are strongly recommended to read this summary when you 
start out to learn how to use PYTHIA 8.2. 
 
<p/> 
For the physics description we refer to the complete 
<br/><b>PYTHIA 6.4 Physics and Manual</b> 
<br/>T. Sj&ouml;strand, S. Mrenna and P. Skands, JHEP05 (2006) 026, 
<br/>which in detail describes the physics (largely) implemented also in 
PYTHIA 8, and also provides a more extensive bibliography than found 
here. When you use PYTHIA 8.2, you should therefore cite both. 
 
<p/> 
Furthermore, a separate 
<br/><a href="../pdfdoc/worksheet8200.pdf" target="page"> 
<b>PYTHIA 8.2 Worksheet</b></a>, 
<br/>also an attached PDF file, offers a practical introduction to 
using the generator. It has been developed for and used at a few 
summer schools, with minor variations, but is also suited for 
self-study. 
 
<h3>Authors</h3> 
 
<p/> 
<b>Christian Bierlich</b><br/> 
Department of Astronomy and Theoretical Physics, Lund University, 
S&ouml;lvegatan 14A, SE-223 62 Lund, Sweden<br/> 
and Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark<br/> 
e-mail: christian.bierlich@thep.lu.se 
 
<p/> 
<b>Nishita Desai</b><br/> 
Department of Theoretical Physics, Tata Institute of Fundamental Research, 
Homi Bhabha Road, Mumbai 400005, India<br/> 
e-mail: desai@theory.tifr.res.in 
 
<p/> 
<b>Leif Gellersen</b><br/> 
Department of Astronomy and Theoretical Physics, Lund University, 
S&ouml;lvegatan 14A, SE-223 62 Lund, Sweden<br/> 
e-mail: leif.gellersen@thep.lu.se 
 
<p/> 
<b>Ilkka Helenius</b><br/> 
Department of Physics, University of Jyv&auml;skyl&auml;, P.O. Box 35, 
FI-40014 University of Jyv&auml;skyl&auml;, Finland<br/> 
e-mail: ilkka.m.helenius@jyu.fi 
 
<p/> 
<b>Philip Ilten</b><br/> 
Department of Physics, University of Cincinnati, 
Cincinnati, OH 45221, USA<br/> 
and School of Physics and Astronomy, University of Birmingham, 
Birmingham, B152 2TT, UK<br/> 
e-mail: philten@cern.ch 
 
<p/> 
<b>Leif L&ouml;nnblad</b><br/> 
Department of Astronomy and Theoretical Physics, Lund University, 
S&ouml;lvegatan 14A, SE-223 62 Lund, Sweden<br/> 
e-mail: leif.lonnblad@thep.lu.se 
 
<p/> 
<b>Stephen Mrenna</b><br/> 
Computing Division, Simulations Group, 
Fermi National Accelerator Laboratory, 
MS 234, Batavia, IL 60510, USA<br/> 
e-mail: mrenna@fnal.gov 
 
<p/> 
<b>Stefan Prestel</b><br/> 
Department of Astronomy and Theoretical Physics, Lund University, 
S&ouml;lvegatan 14A, SE-223 62 Lund, Sweden<br/> 
e-mail: stefan.prestel@thep.lu.se 
 
<p/> 
<b>Christine O. Rasmussen</b><br/> 
Department of Astronomy and Theoretical Physics, Lund University, 
S&ouml;lvegatan 14A, SE-223 62 Lund, Sweden<br/> 
e-mail: christine.rasmussen@thep.lu.se 
 
<p/> 
<b>Torbj&ouml;rn Sj&ouml;strand</b><br/> 
Department of Astronomy and Theoretical Physics, Lund University, 
S&ouml;lvegatan 14A, SE-223 62 Lund, Sweden<br/> 
e-mail: torbjorn@thep.lu.se 
 
<p/> 
<b>Peter Skands</b><br/> 
School of Physics and Astronomy, Monash University, PO Box 27, 3800 Melbourne, 
Australia<br/> 
e-mail: peter.skands@monash.edu 
 
<p/> 
<b>Marius Utheim</b><br/> 
Department of Astronomy and Theoretical Physics, Lund University, 
S&ouml;lvegatan 14A, SE-223 62 Lund, Sweden<br/> 
e-mail: marius.utheim@thep.lu.se 
 
<h3>Former authors</h3> 
 
<p/><b>Stefan Ask</b> 
 
<p/><b>Jesper Roy Christiansen</b> 
 
<p/><b>Richard Corke</b> 
 
<p/><b>Nadine Fischer</b> 
 
<p/><b>Christine O. Rasmussen</b> 
 
<h3>Further contributions</h3> 
 
Makefiles, configure scripts and HepMC interface by <b>Mikhail Kirsanov</b>. 
<br/>Conversion of XML files to PHP ones by <b>Ben Lloyd</b>. 
<br/>Simple Makefile for Win32/NMAKE by <b>Bertrand Bellenot</b>. 
<br/>Extended Higgs sector partly implemented by <b>Marc Montull</b>. 
<br/>Parts of charm and bottom decay tables courtesy <b>DELPHI</b> and 
<b>LHCb</b> collaborations. 
<br/>Tunes and comparisons with data, based on Rivet and Professor, 
by <b>Hendrik Hoeth</b>. 
<br/>Text and code on the use of ROOT in conjunction with PYTHIA 
by <b>Rene Brun</b>, <b>Andreas Morsch</b> and <b>Axel Naumann</b>. 
<br/>Code and data for MRST/MSTW PDFs by <b>Robert Thorne</b> and 
<b>Graeme Watt</b>. 
<br/>Code and data for the CTEQ/CT PDFs by <b>Joey Huston</b> 
and colleagues. 
<br/>Help with implementing new proton PDFs by <b>Tomas Kasemets</b>. 
<br/>Code and data for Pomeron PDFs by <b>H1</b> collaboration and 
especially <b>Paul Newman</b>. 
<br/>Help with implementing new Pomeron fluxes and PDFs by 
<b>Sparsh Navin</b>. 
<br/>The new Hidden Valley code developed together with <b>Lisa Carloni</b>. 
<br/>Code for a Kaluza-Klein electroweak gauge boson provided by 
<b>Noam Hod</b> and <b>Mark Sutton</b>. 
<br/>Code for equivalent photon flux around an unresolved proton by 
<b>Oystein Alvestad</b>. 
<br/>The MBR diffractive model and central diffraction by 
<b>Robert Ciesielski</b>. 
<br/>2012 branching ratios for most light hadrons, and the tau lepton, 
by <b>Anil Pratap Singh</b>. 
<br/>The pythia8-config script has been contributed by 
<b>Andy Buckley</b>, along with many other helpful suggestions. 
<br/>Code and data for several of the NNPDF2.3 QCD+QED sets, and further 
later ones, provided by <b>Juan Rojo</b> and <b>Stefano Carrazza</b>. 
<br/>The fjcore code from FastJet provided by <b>Matteo Cacciari</b>, 
<b>Gavin Salam</b> and <b>Gregory Soyez</b>. 
<br/>The initial-final dipole approach has been developed and 
implemented by <b>Baptiste Cabouat</b>. 
<br/>The MixMax random number generator has been contributed by 
<b>Konstantin Savvidy</b> and <b>George Savvidy</b>. 
<br/>Space-time hadronic production points in string fragmentation have 
been studied and implemented by <b>Silvia Ferreres-Sol&eacute;</b>. 
<br/>The code for deuteron production was tested by <b>Sophie Baker</b>. 
<br/>C++ interface to MG5 matrix elements by <b>V. Hirschi</b> with 
additional work by <b>O. Mattelaer</b>. 
<br/>Mass corrections and initial-state showers in Vincia by 
<b>M. Ritzmann</b>. 
<br/>Final-state sector showers in Vincia by <b>J. Lopez-Villarejo</b>. 
<br/>Helicity-dependence in Vincia by <b>A. Larkoski</b>. 
<br/>QED and Electroweak showers in Vincia by <b>R. Verheyen</b>. 
<br/>Interleaved resonance showers and work on 
sector merging and QED+EW showers in Vincia by <b>H. Brooks</b>. 
<br/> 
 
<br/><b>Note</b>: in several cases modifications have been made to 
the original code, in order to integrate it with PYTHIA. In these cases 
the blame for any mistakes has to rest with the regular authors. 
 
<h3>Licence</h3> 
 
PYTHIA 8 is licensed under the 
<a href="COPYING" target="page"><b>GNU General Public Licence 
version 2</b></a> or later. 
<br/>Please respect the 
<a href="GUIDELINES" target="page"><b>MCnet Guidelines</b></a> 
for Event Generator Authors and Users. 
 
<p/> 
The program and the documentation is 
Copyright &copy; 2019 Torbj&ouml;rn Sj&ouml;strand 
 
 
</chapter> 
 
<!-- Copyright (C) 2020 Torbjorn Sjostrand --> 
