<chapter name="Program Classes"> 
 
<h2>Program Classes</h2> 
 
The complete PYTHIA 8 package contains 
<aloc href="ProgramFiles">a multitude of classes</aloc>. 
There is no reason to describe all of them, with all of their 
methods, since most should not be touched by a normal user. 
Nevertheless some of the crucial ones are described in detail, 
as a help not only to advanced users but also to developers. 
We here provide a quick reference (still incomplete) which 
classes you can find described where on these pages. Normally 
you have to scroll down to find the details, since the top of 
the page contains information of more general interest. 
 
<p/> 
<table cellspacing="5"> 
 
<tr> 
<td><b>Class</b></td> 
<td><b>Reference</b></td> 
<td><b>Comment</b></td> 
</tr> 
 
<tr> 
<td><code>BeamShape</code></td> 
<td><aloc href="BeamShape">Beam Shape</aloc></td> 
<td>vertex and beam momentum spread</td> 
</tr> 
 
<tr> 
<td><code>CellJet</code></td> 
<td><aloc href="EventAnalysis">Event Analysis</aloc></td> 
<td>jet cone clustering analysis, intended for hadron collider 
topologies</td> 
</tr> 
 
<tr> 
<td><code>ClusterJet</code></td> 
<td><aloc href="EventAnalysis">Event Analysis</aloc></td> 
<td>jet clustering analysis, intended for <ei>e^+e^-</ei> 
collider topologies</td> 
</tr> 
 
<tr> 
<td><code>CoupSM</code></td> 
<td><aloc href="StandardModelParameters">Standard Model Parameters</aloc></td> 
<td>couplings and mixing matrices</td> 
</tr> 
 
<tr> 
<td><code>CoupSUSY</code></td> 
<td><aloc href="SUSYLesHouchesAccord">SUSY Les Houches Accord</aloc></td> 
<td>compute and store SUSY couplings, using input from SusyLesHouches</td> 
</tr> 
 
<tr> 
<td><code>DecayChannel</code></td> 
<td><aloc href="ParticleDataScheme">Particle Data Scheme</aloc></td> 
<td>the properties of a single decay channel of  particle species</td> 
</tr> 
 
<tr> 
<td><code>Event</code></td> 
<td><aloc href="EventRecord">Event Record</aloc></td> 
<td>the complete event record</td> 
</tr> 
 
<tr> 
<td><code>Hist</code></td> 
<td><aloc href="Histograms">Histograms</aloc></td> 
<td>a primitive built-in histogramming package</td> 
</tr> 
 
<tr> 
<td><code>Info</code></td> 
<td><aloc href="EventInformation">Event Information</aloc></td> 
<td>various one-of-a-kind information on the current event</td> 
</tr> 
 
<tr> 
<td><code>LHAup</code></td> 
<td><aloc href="LHA">Les Houches Accord</aloc></td> 
<td>base class for Les Houches external hard-event input</td> 
</tr> 
 
<tr> 
<td><code>Particle</code></td> 
<td><aloc href="ParticleProperties">Particle Properties</aloc></td> 
<td>the properties of a particle in the event record</td> 
</tr> 
 
<tr> 
<td><code>ParticleData</code></td> 
<td><aloc href="ParticleDataScheme">Particle Data Scheme</aloc></td> 
<td>the database of particle species properties</td> 
</tr> 
 
<tr> 
<td><code>ParticleDataEntry</code></td> 
<td><aloc href="ParticleDataScheme">Particle Data Scheme</aloc></td> 
<td>the properties of a particle species</td> 
</tr> 
 
<tr> 
<td><code>PDF</code></td> 
<td><aloc href="PartonDistributions">Parton Distributions</aloc></td> 
<td>base class for all PDFs</td> 
</tr> 
 
<tr> 
<td><code>Pythia</code></td> 
<td><aloc href="ProgramFlow">Program Flow</aloc></td> 
<td>the top-level class, that drives the generation process</td> 
</tr> 
 
<tr> 
<td><code>ResonanceWidths</code></td> 
<td><aloc href="SemiInternalResonances">Semi-Internal Resonances</aloc></td> 
<td>base class for all resonance-width treatment</td> 
</tr> 
 
<tr> 
<td><code>Rndm</code></td> 
<td><aloc href="RandomNumbers">RandomNumbers</aloc></td> 
<td>a primitive built-in histogramming package</td> 
</tr> 
 
<tr> 
<td><code>RotBstMatrix</code></td> 
<td><aloc href="FourVectors">Four-Vectors</aloc></td> 
<td>rotation and boosts of four-vectors</td> 
</tr> 
 
<tr> 
<td><code>Settings</code></td> 
<td><aloc href="SettingsScheme">Settings Scheme</aloc></td> 
<td>the database that regulates the behaviour of the program</td> 
</tr> 
 
<tr> 
<td><code>SigmaProcess</code></td> 
<td><aloc href="SemiInternalProcesses">Semi-Internal Processes</aloc></td> 
<td>base class for all hard-process cross sections</td> 
</tr> 
 
<tr> 
<td><code>SlowJet</code></td> 
<td><aloc href="EventAnalysis">Event Analysis</aloc></td> 
<td>simple jet clustering using the <ei>kT</ei>, anti-<ei>kT</ei> or 
Cambridge/Aachen algorithms.</td> 
</tr> 
 
<tr> 
<td><code>SpaceShower</code></td> 
<td><aloc href="ImplementNewShowers">Implement New Showers</aloc></td> 
<td>spacelike, i..e. initial-state showers</td> 
</tr> 
 
<tr> 
<td><code>Sphericity</code></td> 
<td><aloc href="EventAnalysis">Event Analysis</aloc></td> 
<td>sphericity analysis of events</td> 
</tr> 
 
<tr> 
<td><code>SusyLesHouches</code></td> 
<td><aloc href="SUSYLesHouchesAccord">SUSY Les Houches Accord</aloc></td> 
<td>reading in of SLHA information</td> 
</tr> 
 
<tr> 
<td><code>Thrust</code></td> 
<td><aloc href="EventAnalysis">Event Analysis</aloc></td> 
<td>thrust analysis of events</td> 
</tr> 
 
<tr> 
<td><code>TimeShower</code></td> 
<td><aloc href="ImplementNewShowers">Implement New Showers</aloc></td> 
<td>timelike, i..e. final-state showers</td> 
</tr> 
 
<tr> 
<td><code>UserHooks</code></td> 
<td><aloc href="UserHooks">User Hooks</aloc></td> 
<td>get access to some steps of the generation process</td> 
</tr> 
 
<tr> 
<td><code>Vec4</code></td> 
<td><aloc href="FourVectors">Four-Vectors</aloc></td> 
<td>four-vectors</td> 
</tr> 
 
<tr> 
<td><code></code></td> 
<td><aloc href=""></aloc></td> 
<td></td> 
</tr> 
 
<tr> 
<td><code></code></td> 
<td><aloc href=""></aloc></td> 
<td></td> 
</tr> 
 
</table> 
 
<p/> 
You can also access an extensive list of the public 
<aloc href="ProgramMethods">methods</aloc> in these classes, 
which compensates for the brevity of the current page. 
 
</chapter> 
 
<!-- Copyright (C) 2020 Torbjorn Sjostrand --> 
