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| 2 | <head> |
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| 3 | <title>Program Files</title> |
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| 4 | <link rel="stylesheet" type="text/css" href="pythia.css"/> |
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| 5 | <link rel="shortcut icon" href="pythia32.gif"/> |
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| 6 | </head> |
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| 7 | <body> |
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| 8 | |
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| 9 | <h2>Program Files</h2> |
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| 10 | |
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| 11 | The code is subdivided into a set of files, mainly by physics |
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| 12 | task. Each file typically contains one main class, but often |
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| 13 | with a few related helper classes that are not used elsewhere in |
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| 14 | the program. Normally the files come in pairs. |
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| 15 | <ul> |
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| 16 | <li>A header file, <code>.h</code> in the <code>include</code> |
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| 17 | subdirectory, where the public interface of the class is declared, |
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| 18 | and inline methods are defined.</li> |
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| 19 | <li>A source code file, <code>.cc</code> in the <code>src</code> |
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| 20 | subdirectory, where most of the methods are implemented.</li> |
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| 21 | </ul> |
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| 22 | During compilation, related dependency files, <code>.d</code>, and |
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| 23 | compiled code, <code>.o</code> are created in the <code>tmp</code> |
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| 24 | subdirectory. |
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| 25 | |
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| 26 | <p/> |
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| 27 | In part the <code>.xml</code> documentation files in the |
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| 28 | <code>xmldoc</code> subdirectory have matching names, but the match |
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| 29 | is broken by the desire to group topics more by user interaction than |
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| 30 | internal operation. On these pages the function of the different code |
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| 31 | files is summarized. Currently, each <code>.xml</code> file is also |
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| 32 | translated into an <code>.html</code> one in the |
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| 33 | <code>htmldoc</code> subdirectory, to allow easy viewing of the |
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| 34 | contents in a web browser, and an <code>.php</code> one in |
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| 35 | <code>phpdoc</code>, for more sophisticated interactivity |
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| 36 | if that subdirectory is installed on a web server. |
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| 37 | |
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| 38 | <p/> |
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| 39 | Here is the current list of files, ordered alphabetically, with a brief |
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| 40 | description of contents. |
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| 41 | |
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| 42 | <p/><code>file </code><strong> Analysis </strong> <br/> |
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| 43 | contains routines to analyze events. Currently it can do sphericity, |
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| 44 | thrust, Lund/Jade/Durham jet clustering, cone-jet finding, and the |
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| 45 | <i>kT</i>, anti-<i>kT</i> and Cambridge/Aachen algorithms for |
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| 46 | hadron colliders. |
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| 47 | |
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| 48 | |
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| 49 | <p/><code>file </code><strong> Basics </strong> <br/> |
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| 50 | contains some basic facilities of general use: a random number |
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| 51 | generator <code>Rndm</code>, a four-vector class <code>Vec4</code>, and a |
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| 52 | histogram class <code>Hist</code>. |
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| 53 | |
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| 54 | |
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| 55 | <p/><code>file </code><strong> BeamParticle </strong> <br/> |
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| 56 | contains information on all partons extracted from one of the two |
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| 57 | beams. Defines modified parton distributions accordingly during the |
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| 58 | showering and multiparton interactions processing, thereby extending on |
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| 59 | the one-particle-inclusive distributions defined by the previous class. |
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| 60 | Finds the internal structure for a beam remnant. |
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| 61 | |
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| 62 | |
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| 63 | <p/><code>file </code><strong> BeamRemnants </strong> <br/> |
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| 64 | adds primordial <i>kT</i> to the set of hard subsystems, |
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| 65 | and combines these subsystems with the two beam remnants to provide |
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| 66 | the overall energy-momentum picture. Also ties together all the |
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| 67 | colour lines into consistent singlets. |
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| 68 | |
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| 69 | |
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| 70 | <p/><code>file </code><strong> BeamShape </strong> <br/> |
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| 71 | generates momentum spread of beams, and spread of collision vertex |
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| 72 | position. |
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| 73 | |
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| 74 | |
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| 75 | <p/><code>file </code><strong> BoseEinstein </strong> <br/> |
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| 76 | provides a simple method to impose Bose-Einstein correlations on |
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| 77 | pairs of identical mesons. |
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| 78 | |
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| 79 | |
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| 80 | <p/><code>file </code><strong> Event </strong> <br/> |
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| 81 | contains the event record, which basically is a vector of particles. |
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| 82 | This file also contains the <code>Particle</code> class, used by |
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| 83 | <code>Event</code>. <code>Pythia</code> uses two <code>Event</code> |
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| 84 | objects, one for the process-level record (<code>process</code>) and |
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| 85 | one for the complete event (<code>event</code>). |
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| 86 | |
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| 87 | |
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| 88 | <p/><code>file </code><strong> FragmentationFlavZpT </strong> <br/> |
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| 89 | contains the classes for describing the fragmentation steps in |
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| 90 | flavour and in longitudinal and transverse momentum. |
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| 91 | |
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| 92 | |
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| 93 | <p/><code>file </code><strong> FragmentationSystems </strong> <br/> |
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| 94 | defines some containers of parton systems, for use in |
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| 95 | the fragmentation routines. |
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| 96 | |
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| 97 | |
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| 98 | <p/><code>file </code><strong> HadronLevel </strong> <br/> |
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| 99 | turns the parton-level event above into a set of outgoing particles, |
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| 100 | by applying string fragmentation (with special treatment for low-mass |
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| 101 | systems) and secondary decays, and optionally Bose-Einstein corrections. |
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| 102 | |
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| 103 | |
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| 104 | <p/><code>file </code><strong> HelicityBasics </strong> <br/> |
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| 105 | basic classes for the handling of helicities in tau lepton decays. |
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| 106 | |
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| 107 | |
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| 108 | <p/><code>file </code><strong> HelicityMatrixElements </strong> <br/> |
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| 109 | helicity-dependent decay matrix elements for the tau lepton. |
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| 110 | |
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| 111 | |
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| 112 | <p/><code>file </code><strong> HepMCInterface </strong> <br/> |
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| 113 | contains an interface to convert the PYTHIA 8 event record into the |
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| 114 | HepMC format. The <code>HepMCInterface.cc</code> file is located in |
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| 115 | the subdirectory <code>hepmcinterface</code> and is used to build a |
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| 116 | separate <code>libhepmcinterface</code> library. |
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| 117 | |
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| 118 | |
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| 119 | <p/><code>file </code><strong> HiddenValleyFragmentation </strong> <br/> |
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| 120 | hadronization in models with a hidden sector that contains an unbroken |
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| 121 | <i>SU(N)</i>, which gives confinement. The model and code is largely |
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| 122 | derived from the normal fragmentation classes. |
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| 123 | |
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| 124 | |
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| 125 | <p/><code>file </code><strong> History </strong> <br/> |
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| 126 | methods to reconstruct the imagined shower history of a |
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| 127 | matrix-element-generated multiparton configuration, as part of |
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| 128 | the CKKW-L matrix element merging. |
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| 129 | |
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| 130 | |
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| 131 | <p/><code>file </code><strong> Info </strong> <br/> |
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| 132 | is a simple container that gives access to some information on the |
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| 133 | nature of the current process, such as Mandelstam variables. |
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| 134 | Also contains a small database for errors and warnings encountered |
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| 135 | during program execution. |
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| 136 | |
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| 137 | |
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| 138 | <p/><code>file </code><strong> LesHouches </strong> <br/> |
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| 139 | gives the possibility to feed in parton configurations for the |
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| 140 | subsequent event generation. One base class is defined, with containers |
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| 141 | for initialization and event information, that can be read from |
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| 142 | <code>Pythia</code>. Derived classes allow for a few different cases. |
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| 143 | |
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| 144 | |
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| 145 | <p/><code>file </code><strong> LHAFortran </strong> <br/> |
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| 146 | is a header file only, for a class derived from the above LesHouches |
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| 147 | one, to be used for runtime interfacing to Fortran programs, such as |
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| 148 | PYTHIA 6. |
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| 149 | |
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| 150 | |
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| 151 | <p/><code>file </code><strong> LHAPDFInterface </strong> <br/> |
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| 152 | is a header file only, with interfaces to the key LHAPDF routines, |
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| 153 | as needed for a runtime interface. There is a file |
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| 154 | <code>lhapdfdummy/LHAPDFdummy.cc</code> with matching dummy |
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| 155 | implementations, however. This file is used to build a separate |
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| 156 | <code>liblhapdfdummy</code> library, to be linked when the LHAPDF |
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| 157 | library is not used, so as to avoid problems with undefined references. |
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| 158 | |
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| 159 | |
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| 160 | <p/><code>file </code><strong> MergingHooks </strong> <br/> |
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| 161 | intercede in the normal shower evolution to construct the relevant |
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| 162 | Sudakov form factor suppressions as part of the CKKW-L matrix element |
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| 163 | merging. |
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| 164 | |
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| 165 | |
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| 166 | <p/><code>file </code><strong> MiniStringFragmentation </strong> <br/> |
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| 167 | performs string fragmentation in cases where the colour singlet |
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| 168 | subsystem mass is so small that one or at most two primary hadrons |
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| 169 | should be produced from it. |
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| 170 | |
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| 171 | |
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| 172 | <p/><code>file </code><strong> MultipartonInteractions </strong> <br/> |
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| 173 | performs multiparton interactions. |
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| 174 | |
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| 175 | |
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| 176 | <p/><code>file </code><strong> ParticleData </strong> <br/> |
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| 177 | contains a database of all necessary particle data (masses, names, ..) |
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| 178 | and decay channels. |
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| 179 | |
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| 180 | |
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| 181 | <p/><code>file </code><strong> ParticleDecays </strong> <br/> |
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| 182 | performs the decays of all normal unstable hadrons and leptons, i.e. |
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| 183 | in mass up to and including <i>b bbar</i> systems. It is not |
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| 184 | intended for decays of electroweak resonances, like <i>Z^0</i>. |
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| 185 | |
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| 186 | |
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| 187 | <p/><code>file </code><strong> PartonDistributions </strong> <br/> |
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| 188 | contains parton distribution functions for the proton and electron. |
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| 189 | Currently very simple, with only two <i>p</i> parametrizations |
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| 190 | and one <i>e</i> ditto available, but it is possible to link in |
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| 191 | external sets. |
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| 192 | |
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| 193 | |
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| 194 | <p/><code>file </code><strong> PartonLevel </strong> <br/> |
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| 195 | turns the (hard) process above into a complete set of partons, by |
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| 196 | adding initial- and final-state radiation, multiparton |
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| 197 | interactions, and beam remnants. |
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| 198 | |
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| 199 | |
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| 200 | <p/><code>file </code><strong> PartonSystems </strong> <br/> |
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| 201 | keeps track of which partons belong to which partonic subsystem, |
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| 202 | i.e. one of the multiparton (semi)hard interactions with associated |
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| 203 | showers. |
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| 204 | |
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| 205 | |
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| 206 | <p/><code>file </code><strong> PhaseSpace </strong> <br/> |
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| 207 | selects a point in phase space for the hard-process generation, |
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| 208 | optimized separately for each process to give improved Monte Carlo |
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| 209 | efficiency. |
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| 210 | |
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| 211 | |
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| 212 | <p/><code>file </code><strong> ProcessContainer </strong> <br/> |
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| 213 | packages the information on a given subprocess, combining the |
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| 214 | phase-space selection and cross-section evaluation machineries |
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| 215 | with some statistics information. Also sets up the list of processes |
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| 216 | to be studied in a run. |
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| 217 | |
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| 218 | |
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| 219 | <p/><code>file </code><strong> ProcessLevel </strong> <br/> |
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| 220 | handles the generation of the (hard) process that sets the character |
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| 221 | of the event. This involves either using internally implemented |
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| 222 | processes or linking to Les Houches information. The latter can |
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| 223 | be by runtime interfaces or by reading in a file. This step also |
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| 224 | includes resonance decays. |
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| 225 | |
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| 226 | |
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| 227 | <p/><code>file </code><strong> Pythia </strong> <br/> |
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| 228 | is the main class, that administrates the whole event generation |
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| 229 | process by making use of all the others classes. Objects of most |
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| 230 | other classes reside (directly or indirectly) inside <code>Pythia</code>, |
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| 231 | so only a <code>Pythia</code> object needs to be explicitly instantiated |
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| 232 | and addressed by the user. |
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| 233 | |
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| 234 | |
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| 235 | <p/><code>file </code><strong> PythiaComplex </strong> <br/> |
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| 236 | is only a <code>.h</code> file, containing a <code>typedef</code> for |
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| 237 | double precision complex numbers. |
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| 238 | |
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| 239 | |
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| 240 | <p/><code>file </code><strong> PythiaStdlib </strong> <br/> |
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| 241 | contains most of the <code>Stdlib</code> headers used in PYTHIA 8, |
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| 242 | with <code>using</code> directives. It defines <code>M_PI</code> if |
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| 243 | this is not already done. Also a few simple inline methods: |
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| 244 | <code>pow2(x)</code>, <code>pow3(x)</code>, <code>pow4(x)</code>, |
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| 245 | <code>pow5(x)</code> and <code>pow6(x)</code> for small integer |
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| 246 | powers, and <code>sqrtpos(x)</code> where a <code>max(0., x)</code> |
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| 247 | ensures that one does not take the square root of a negative number. |
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| 248 | Also non-inlined <code>GammaReal(x)</code> for the <i>Gamma</i> |
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| 249 | function value of a real argument. |
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| 250 | |
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| 251 | |
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| 252 | <p/><code>file </code><strong> ResonanceDecays </strong> <br/> |
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| 253 | decays resonances as part of the hard-process stage, in many cases |
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| 254 | (but not all) including angular correlations between the decay products. |
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| 255 | |
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| 256 | |
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| 257 | <p/><code>file </code><strong> ResonanceWidths </strong> <br/> |
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| 258 | encodes some properties of resonances, in particular the dynamic |
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| 259 | calculation of widths. |
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| 260 | |
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| 261 | |
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| 262 | <p/><code>file </code><strong> RHadrons </strong> <br/> |
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| 263 | handles the production and decay of hadrons formed by long-lived |
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| 264 | gluinos, stops or sbottoms. |
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| 265 | |
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| 266 | |
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| 267 | <p/><code>file </code><strong> Settings </strong> <br/> |
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| 268 | contains a database of all flags, modes, parameters and words that |
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| 269 | determine the performance of the generator. Initial values are obtained |
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| 270 | from the contents of the <code>.xml</code> files, but these values can |
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| 271 | then be changed by the user. |
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| 272 | |
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| 273 | |
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| 274 | <p/><code>file </code><strong> SigmaCompositeness </strong> <br/> |
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| 275 | contains the cross sections and matrix elements for production of |
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| 276 | some particles in compositeness scenarios, specifically excited |
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| 277 | fermions. |
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| 278 | |
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| 279 | |
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| 280 | <p/><code>file </code><strong> SigmaEW </strong> <br/> |
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| 281 | contains the cross sections and matrix elements for electroweak |
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| 282 | processes involving photons, <i>Z^0</i>'s and <i>W^+-</i>'s. |
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| 283 | |
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| 284 | |
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| 285 | <p/><code>file </code><strong> SigmaExtraDim </strong> <br/> |
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| 286 | contains the cross sections and matrix elements for processes in |
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| 287 | scenarios involving extra dimensions. |
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| 288 | |
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| 289 | |
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| 290 | <p/><code>file </code><strong> SigmaGeneric </strong> <br/> |
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| 291 | contains the cross sections and matrix elements for some generic |
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| 292 | processes, to be used as building blocks for a few BSM scenarios. |
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| 293 | |
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| 294 | |
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| 295 | <p/><code>file </code><strong> SigmaHiggs </strong> <br/> |
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| 296 | contains the cross sections and matrix elements for Higgs production. |
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| 297 | |
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| 298 | |
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| 299 | <p/><code>file </code><strong> SigmaLeftRightSym </strong> <br/> |
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| 300 | contains the cross sections and matrix elements for particle production |
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| 301 | in left-right-symmetry scenarios, specifically righthanded <i>Z</i> |
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| 302 | and <i>W</i> bosons and doubly-charged Higgs bosons. |
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| 303 | |
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| 304 | |
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| 305 | <p/><code>file </code><strong> SigmaLeptoquark </strong> <br/> |
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| 306 | contains the cross sections and matrix elements for leptoquark production. |
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| 307 | |
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| 308 | |
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| 309 | <p/><code>file </code><strong> SigmaNewGaugeBosons </strong> <br/> |
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| 310 | contains the cross sections and matrix elements for a <i>Z'^0</i>, |
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| 311 | a <i>W^+-</i> and a horizontal gauge boson <i>R^0</i>. |
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| 312 | |
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| 313 | |
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| 314 | <p/><code>file </code><strong> SigmaOnia </strong> <br/> |
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| 315 | contains the cross sections and matrix elements for charmonium and |
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| 316 | bottomonium production. |
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| 317 | |
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| 318 | |
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| 319 | <p/><code>file </code><strong> SigmaProcess </strong> <br/> |
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| 320 | contains the base class and derived classes for the evaluation of |
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| 321 | different matrix elements. Also keeps track of allowed incoming |
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| 322 | parton configurations and their cross sections, including parton |
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| 323 | densities. In order to keep this file from becoming too big, actual |
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| 324 | cross sections are found in several separate files of derived classes: |
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| 325 | <code>SigmaQCD</code>, <code>SigmaEW</code>, <code>SigmaOnia</code>, |
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| 326 | <code>SigmaHiggs</code>, <code>SigmaSUSY</code>, |
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| 327 | <code>SigmaNewGaugeBosons</code>, <code>SigmaLeftRightSym</code>, |
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| 328 | <code>SigmaLeptoquark</code>, <code>SigmaCompositeness</code>, |
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| 329 | <code>SigmaExtraDim</code> and <code>SigmaGeneric</code>. |
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| 330 | |
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| 331 | |
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| 332 | <p/><code>file </code><strong> SigmaQCD </strong> <br/> |
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| 333 | contains the cross sections and matrix elements for soft and hard |
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| 334 | QCD processes. |
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| 335 | |
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| 336 | |
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| 337 | <p/><code>file </code><strong> SigmaSUSY </strong> <br/> |
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| 338 | contains the cross sections and matrix elements for Supersymmetric |
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| 339 | processes. |
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| 340 | |
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| 341 | |
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| 342 | <p/><code>file </code><strong> SigmaTotal </strong> <br/> |
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| 343 | contains parametrizations of total, elastic and diffractive hadronic |
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| 344 | cross sections. |
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| 345 | |
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| 346 | |
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| 347 | <p/><code>file </code><strong> SpaceShower </strong> <br/> |
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| 348 | performs spacelike initial-state transverse-momentum-ordered |
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| 349 | shower evolution. |
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| 350 | |
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| 351 | |
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| 352 | <p/><code>file </code><strong> StandardModel </strong> <br/> |
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| 353 | contains the running <i>alpha_strong</i>, with <i>Lambda</i> |
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| 354 | matching at flavour thresholds, the running <i>alpha_em</i>, |
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| 355 | CKM mixing matrices, and a few other parameters such as |
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| 356 | <i>sin^2(theta_W)</i>. |
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| 357 | |
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| 358 | |
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| 359 | <p/><code>file </code><strong> StringFragmentation </strong> <br/> |
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| 360 | performs string fragmentation of a given set of partons. |
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| 361 | |
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| 362 | |
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| 363 | <p/><code>file </code><strong> SusyCouplings </strong> <br/> |
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| 364 | stores the various couplings used for SUSY cross sections and |
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| 365 | decays, as calculated from input e.g. based on the SUSY Les Houches |
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| 366 | Accord. |
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| 367 | |
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| 368 | |
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| 369 | <p/><code>file </code><strong> SusyLesHouches </strong> <br/> |
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| 370 | contains information on SUSY parameters and particle data as specified |
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| 371 | by the SUSY Les Houches Accord. |
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| 372 | |
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| 373 | |
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| 374 | <p/><code>file </code><strong> TauDecays </strong> <br/> |
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| 375 | the main routines for handling tau lepton decays with helicity |
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| 376 | information. |
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| 377 | |
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| 378 | |
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| 379 | <p/><code>file </code><strong> TimeShower </strong> <br/> |
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| 380 | performs timelike final-state transverse-momentum-ordered |
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| 381 | shower evolution. |
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| 382 | |
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| 383 | |
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| 384 | <p/><code>file </code><strong> UserHooks </strong> <br/> |
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| 385 | Provides a way for a user to study the event at a few intermediate |
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| 386 | stages of evolution, to reject the event as a whole or to modify |
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| 387 | its cross-section weight. |
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| 388 | |
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| 389 | |
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| 390 | </body> |
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| 391 | </html> |
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| 392 | |
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| 393 | <!-- Copyright (C) 2012 Torbjorn Sjostrand --> |
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