<html> <head> <title>Program Files</title> <link rel="stylesheet" type="text/css" href="pythia.css"/> <link rel="shortcut icon" href="pythia32.gif"/> </head> <body> <h2>Program Files</h2> The code is subdivided into a set of files, mainly by physics task. Each file typically contains one main class, but often with a few related helper classes that are not used elsewhere in the program. Normally the files come in pairs. <ul> <li>A header file, <code>.h</code> in the <code>include</code> subdirectory, where the public interface of the class is declared, and inline methods are defined.</li> <li>A source code file, <code>.cc</code> in the <code>src</code> subdirectory, where most of the methods are implemented.</li> </ul> During compilation, related dependency files, <code>.d</code>, and compiled code, <code>.o</code> are created in the <code>tmp</code> subdirectory. <p/> In part the <code>.xml</code> documentation files in the <code>xmldoc</code> subdirectory have matching names, but the match is broken by the desire to group topics more by user interaction than internal operation. On these pages the function of the different code files is summarized. Currently, each <code>.xml</code> file is also translated into an <code>.html</code> one in the <code>htmldoc</code> subdirectory, to allow easy viewing of the contents in a web browser, and an <code>.php</code> one in <code>phpdoc</code>, for more sophisticated interactivity if that subdirectory is installed on a web server. <p/> Here is the current list of files, ordered alphabetically, with a brief description of contents. <p/><code>file </code><strong> Analysis </strong> <br/> contains routines to analyze events. Currently it can do sphericity, thrust, Lund/Jade/Durham jet clustering, cone-jet finding, and the <i>kT</i>, anti-<i>kT</i> and Cambridge/Aachen algorithms for hadron colliders. <p/><code>file </code><strong> Basics </strong> <br/> contains some basic facilities of general use: a random number generator <code>Rndm</code>, a four-vector class <code>Vec4</code>, and a histogram class <code>Hist</code>. <p/><code>file </code><strong> BeamParticle </strong> <br/> contains information on all partons extracted from one of the two beams. Defines modified parton distributions accordingly during the showering and multiparton interactions processing, thereby extending on the one-particle-inclusive distributions defined by the previous class. Finds the internal structure for a beam remnant. <p/><code>file </code><strong> BeamRemnants </strong> <br/> adds primordial <i>kT</i> to the set of hard subsystems, and combines these subsystems with the two beam remnants to provide the overall energy-momentum picture. Also ties together all the colour lines into consistent singlets. <p/><code>file </code><strong> BeamShape </strong> <br/> generates momentum spread of beams, and spread of collision vertex position. <p/><code>file </code><strong> BoseEinstein </strong> <br/> provides a simple method to impose Bose-Einstein correlations on pairs of identical mesons. <p/><code>file </code><strong> Event </strong> <br/> contains the event record, which basically is a vector of particles. This file also contains the <code>Particle</code> class, used by <code>Event</code>. <code>Pythia</code> uses two <code>Event</code> objects, one for the process-level record (<code>process</code>) and one for the complete event (<code>event</code>). <p/><code>file </code><strong> FJcore </strong> <br/> contains the external FJcore package, providing the coure functionality of the FastJet jet fiding package <p/><code>file </code><strong> FragmentationFlavZpT </strong> <br/> contains the classes for describing the fragmentation steps in flavour and in longitudinal and transverse momentum. <p/><code>file </code><strong> FragmentationSystems </strong> <br/> defines some containers of parton systems, for use in the fragmentation routines. <p/><code>file </code><strong> HadronLevel </strong> <br/> turns the parton-level event above into a set of outgoing particles, by applying string fragmentation (with special treatment for low-mass systems) and secondary decays, and optionally Bose-Einstein corrections. <p/><code>file </code><strong> HadronScatter </strong> <br/> contains the beginning of a machinery for final state hadronic rescattering. <p/><code>file </code><strong> HelicityBasics </strong> <br/> basic classes for the handling of helicities in tau lepton decays. <p/><code>file </code><strong> HelicityMatrixElements </strong> <br/> helicity-dependent decay matrix elements for the tau lepton. <p/><code>file </code><strong> HiddenValleyFragmentation </strong> <br/> hadronization in models with a hidden sector that contains an unbroken <i>SU(N)</i>, which gives confinement. The model and code is largely derived from the normal fragmentation classes. <p/><code>file </code><strong> History </strong> <br/> methods to reconstruct the imagined shower history of a matrix-element-generated multiparton configuration, as part of the CKKW-L matrix element merging. <p/><code>file </code><strong> Info </strong> <br/> is a simple container that gives access to some information on the nature of the current process, such as Mandelstam variables. Also contains a small database for errors and warnings encountered during program execution. <p/><code>file </code><strong> LesHouches </strong> <br/> gives the possibility to feed in parton configurations for the subsequent event generation. One base class is defined, with containers for initialization and event information, that can be read from <code>Pythia</code>. Derived classes allow for a few different cases. <p/><code>file </code><strong> LHAFortran </strong> <br/> is a header file only, for a class derived from the above LesHouches one, to be used for runtime interfacing to Fortran programs, such as PYTHIA 6. <p/><code>file </code><strong> LHAPDFInterface </strong> <br/> is a header file only, with interfaces to the key LHAPDF routines, as needed for a runtime interface. There is a file <code>lhapdfdummy/LHAPDFdummy.cc</code> with matching dummy implementations, however. This file is used to build a separate <code>liblhapdfdummy</code> library, to be linked when the LHAPDF library is not used, so as to avoid problems with undefined references. <p/><code>file </code><strong> Merging </strong> <br/> Wpapper class to interface matrix element merging schemes with Pythia. <p/><code>file </code><strong> MergingHooks </strong> <br/> intercede in the normal shower evolution to construct the relevant Sudakov form factor suppressions as part of the CKKW-L matrix element merging. <p/><code>file </code><strong> MiniStringFragmentation </strong> <br/> performs string fragmentation in cases where the colour singlet subsystem mass is so small that one or at most two primary hadrons should be produced from it. <p/><code>file </code><strong> MultipartonInteractions </strong> <br/> performs multiparton interactions. <p/><code>file </code><strong> ParticleData </strong> <br/> contains a database of all necessary particle data (masses, names, ..) and decay channels. <p/><code>file </code><strong> ParticleDecays </strong> <br/> performs the decays of all normal unstable hadrons and leptons, i.e. in mass up to and including <i>b bbar</i> systems. It is not intended for decays of electroweak resonances, like <i>Z^0</i>. <p/><code>file </code><strong> PartonDistributions </strong> <br/> contains parton distribution functions for the proton and electron. Currently very simple, with only two <i>p</i> parametrizations and one <i>e</i> ditto available, but it is possible to link in external sets. <p/><code>file </code><strong> PartonLevel </strong> <br/> turns the (hard) process above into a complete set of partons, by adding initial- and final-state radiation, multiparton interactions, and beam remnants. <p/><code>file </code><strong> PartonSystems </strong> <br/> keeps track of which partons belong to which partonic subsystem, i.e. one of the multiparton (semi)hard interactions with associated showers. <p/><code>file </code><strong> PhaseSpace </strong> <br/> selects a point in phase space for the hard-process generation, optimized separately for each process to give improved Monte Carlo efficiency. <p/><code>file </code><strong> ProcessContainer </strong> <br/> packages the information on a given subprocess, combining the phase-space selection and cross-section evaluation machineries with some statistics information. Also sets up the list of processes to be studied in a run. <p/><code>file </code><strong> ProcessLevel </strong> <br/> handles the generation of the (hard) process that sets the character of the event. This involves either using internally implemented processes or linking to Les Houches information. The latter can be by runtime interfaces or by reading in a file. This step also includes resonance decays. <p/><code>file </code><strong> Pythia </strong> <br/> is the main class, that administrates the whole event generation process by making use of all the others classes. Objects of most other classes reside (directly or indirectly) inside <code>Pythia</code>, so only a <code>Pythia</code> object needs to be explicitly instantiated and addressed by the user. <p/><code>file </code><strong> Pythia8ToHepMC </strong> <br/> contains an interface to convert the PYTHIA 8 event record into the HepMC format. The <code>Pythia8ToHepMC.cc</code> file is located in the subdirectory <code>pythia8tohepmc</code> and is used to build a separate <code>libpythia8tohepmc</code> library. <p/><code>file </code><strong> PythiaComplex </strong> <br/> is only a <code>.h</code> file, containing a <code>typedef</code> for double precision complex numbers. <p/><code>file </code><strong> PythiaStdlib </strong> <br/> contains most of the <code>Stdlib</code> headers used in PYTHIA 8, with <code>using</code> directives. It defines <code>M_PI</code> if this is not already done. Also a few simple inline methods: <code>pow2(x)</code>, <code>pow3(x)</code>, <code>pow4(x)</code>, <code>pow5(x)</code> and <code>pow6(x)</code> for small integer powers, and <code>sqrtpos(x)</code> where a <code>max(0., x)</code> ensures that one does not take the square root of a negative number. Also non-inlined <code>GammaReal(x)</code> for the <i>Gamma</i> function value of a real argument. <p/><code>file </code><strong> ResonanceDecays </strong> <br/> decays resonances as part of the hard-process stage, in many cases (but not all) including angular correlations between the decay products. <p/><code>file </code><strong> ResonanceWidths </strong> <br/> encodes some properties of resonances, in particular the dynamic calculation of widths. <p/><code>file </code><strong> RHadrons </strong> <br/> handles the production and decay of hadrons formed by long-lived gluinos, stops or sbottoms. <p/><code>file </code><strong> Settings </strong> <br/> contains a database of all flags, modes, parameters and words that determine the performance of the generator. Initial values are obtained from the contents of the <code>.xml</code> files, but these values can then be changed by the user. <p/><code>file </code><strong> SigmaCompositeness </strong> <br/> contains the cross sections and matrix elements for production of some particles in compositeness scenarios, specifically excited fermions. <p/><code>file </code><strong> SigmaEW </strong> <br/> contains the cross sections and matrix elements for electroweak processes involving photons, <i>Z^0</i>'s and <i>W^+-</i>'s. <p/><code>file </code><strong> SigmaExtraDim </strong> <br/> contains the cross sections and matrix elements for processes in scenarios involving extra dimensions. <p/><code>file </code><strong> SigmaGeneric </strong> <br/> contains the cross sections and matrix elements for some generic processes, to be used as building blocks for a few BSM scenarios. <p/><code>file </code><strong> SigmaHiggs </strong> <br/> contains the cross sections and matrix elements for Higgs production. <p/><code>file </code><strong> SigmaLeftRightSym </strong> <br/> contains the cross sections and matrix elements for particle production in left-right-symmetry scenarios, specifically righthanded <i>Z</i> and <i>W</i> bosons and doubly-charged Higgs bosons. <p/><code>file </code><strong> SigmaLeptoquark </strong> <br/> contains the cross sections and matrix elements for leptoquark production. <p/><code>file </code><strong> SigmaNewGaugeBosons </strong> <br/> contains the cross sections and matrix elements for a <i>Z'^0</i>, a <i>W^+-</i> and a horizontal gauge boson <i>R^0</i>. <p/><code>file </code><strong> SigmaOnia </strong> <br/> contains the cross sections and matrix elements for charmonium and bottomonium production. <p/><code>file </code><strong> SigmaProcess </strong> <br/> contains the base class and derived classes for the evaluation of different matrix elements. Also keeps track of allowed incoming parton configurations and their cross sections, including parton densities. In order to keep this file from becoming too big, actual cross sections are found in several separate files of derived classes: <code>SigmaQCD</code>, <code>SigmaEW</code>, <code>SigmaOnia</code>, <code>SigmaHiggs</code>, <code>SigmaSUSY</code>, <code>SigmaNewGaugeBosons</code>, <code>SigmaLeftRightSym</code>, <code>SigmaLeptoquark</code>, <code>SigmaCompositeness</code>, <code>SigmaExtraDim</code> and <code>SigmaGeneric</code>. <p/><code>file </code><strong> SigmaQCD </strong> <br/> contains the cross sections and matrix elements for soft and hard QCD processes. <p/><code>file </code><strong> SigmaSUSY </strong> <br/> contains the cross sections and matrix elements for Supersymmetric processes. <p/><code>file </code><strong> SigmaTotal </strong> <br/> contains parametrizations of total, elastic and diffractive hadronic cross sections. <p/><code>file </code><strong> SLHAinterface </strong> <br/> handles the communication between the <code>SusyLesHouches</code> classes and Pythia. <p/><code>file </code><strong> SpaceShower </strong> <br/> performs spacelike initial-state transverse-momentum-ordered shower evolution. <p/><code>file </code><strong> StandardModel </strong> <br/> contains the running <i>alpha_strong</i>, with <i>Lambda</i> matching at flavour thresholds, the running <i>alpha_em</i>, CKM mixing matrices, and a few other parameters such as <i>sin^2(theta_W)</i>. <p/><code>file </code><strong> StringFragmentation </strong> <br/> performs string fragmentation of a given set of partons. <p/><code>file </code><strong> SusyCouplings </strong> <br/> stores the various couplings used for SUSY cross sections and decays, as calculated from input e.g. based on the SUSY Les Houches Accord. <p/><code>file </code><strong> SusyLesHouches </strong> <br/> contains information on SUSY parameters and particle data as specified by the SUSY Les Houches Accord. <p/><code>file </code><strong> SusyResonanceWidths </strong> <br/> encodes some properties of supersymmetric resonances, similar to what <code>ResonanceWidths</code> does for other resonances. <p/><code>file </code><strong> TauDecays </strong> <br/> the main routines for handling tau lepton decays with helicity information. <p/><code>file </code><strong> TimeShower </strong> <br/> performs timelike final-state transverse-momentum-ordered shower evolution. <p/><code>file </code><strong> UserHooks </strong> <br/> Provides a way for a user to study the event at a few intermediate stages of evolution, to reject the event as a whole or to modify its cross-section weight. <p/><code>file </code><strong> WeakShowerMEs </strong> <br/> provides some matrix elements used for ME corrections of <i>W</i> and <i>Z</i> weak gauge boson emission in both initial- and final-state parton showers. </body> </html> <!-- Copyright (C) 2014 Torbjorn Sjostrand -->
