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[u/mrichter/AliRoot.git] / PYTHIA8 / pythia8130 / xmldoc / ProgramFiles.xml
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5ad4eb21 1<chapter name="Program Files">
2
3<h2>Program Files</h2>
4
5The code is subdivided into a set of files, mainly by physics
6task. Each file typically contains one main class, but often
7with a few related helper classes that are not used elsewhere in
8the program. Normally the files come in pairs.
9<ul>
10<li>A header file, <code>.h</code> in the <code>include</code>
11subdirectory, where the public interface of the class is declared,
12and inline methods are defined.</li>
13<li>A source code file, <code>.cc</code> in the <code>src</code>
14subdirectory, where most of the methods are implemented.</li>
15</ul>
16During compilation, related dependency files, <code>.d</code>, and
17compiled code, <code>.o</code> are created in the <code>tmp</code>
18subdirectory.
19
20<p/>
21In part the <code>.xml</code> documentation files in the
22<code>xmldoc</code> subdirectory have matching names, but the match
23is broken by the desire to group topics more by user interaction than
24internal operation. On these pages the function of the different code
25files is summarized. Currently, each <code>.xml</code> file is also
26translated into an <code>.html</code> one in the
27<code>htmldoc</code> subdirectory, to allow easy viewing of the
28contents in a web browser, and an <code>.php</code> one in
29<code>phpdoc</code>, for more sophisticated interactivity
30if that subdirectory is installed on a web server.
31
32<p/>
33Here is the current list of files, ordered alphabetically, with a brief
34description of contents.
35
36<file name="Analysis">
37contains routines to analyze events. Currently it can do sphericity,
38thrust, Lund/Jade/Durham jet clustering, and cone-jet finding.
39</file>
40
41<file name="Basics">
42contains some basic facilities of general use: a random number
43generator <code>Rndm</code>, a four-vector class <code>Vec4</code>, and a
44histogram class <code>Hist</code>.
45</file>
46
47<file name="BeamParticle">
48contains information on all partons extracted from one of the two
49beams. Defines modified parton distributions accordingly during the
50showering and multiple interactions processing, thereby extending on
51the one-particle-inclusive distributions defined by the previous class.
52Finds the internal structure for a beam remnant.
53</file>
54
55<file name="BeamRemnants">
56adds primordial <ei>kT</ei> to the set of hard subsystems,
57and combines these subsystems with the two beam remnants to provide
58the overall energy-momentum picture. Also ties together all the
59colour lines into consistent singlets.
60</file>
61
62<file name="BoseEinstein">
63provides a simple method to impose Bose-Einstein correlations on
64pairs of identical mesons.
65</file>
66
67<file name="Event">
68contains the event record, which basically is a vector of particles.
69This file also contains the <code>Particle</code> class, used by
70<code>Event</code>. <code>Pythia</code> uses two <code>Event</code>
71objects, one for the process-level record (<code>process</code>) and
72one for the complete event (<code>event</code>).
73</file>
74
75<file name="FragmentationFlavZpT">
76contains the classes for describing the fragmentation steps in
77flavour and in longitudinal and transverse momentum.
78</file>
79
80<file name="FragmentationSystems">
81defines some containers of parton systems, for use in
82the fragmentation routines.
83</file>
84
85<file name="HadronLevel">
86turns the parton-level event above into a set of outgoing particles,
87by applying string fragmentation (with special treatment for low-mass
88systems) and secondary decays, and optionally Bose-Einstein corrections.
89</file>
90
91<file name="HepMCInterface">
92contains an interface to convert the PYTHIA 8 event record into the
93HepMC format. The <code>HepMCInterface.cc</code> file is located in
94the subdirectory <code>hepmcinterface</code> and is used to build a
95separate <code>libhepmcinterface</code> library.
96</file>
97
98<file name="Info">
99is a simple container that gives access to some information on the
100nature of the current process, such as Mandelstam variables.
101Also contains a small database for errors and warnings encountered
102during program execution.
103</file>
104
105<file name="LesHouches">
106gives the possibility to feed in parton configurations for the
107subsequent event generation. One base class is defined, with containers
108for initialization and event information, that can be read from
109<code>Pythia</code>. Derived classes allow for a few different cases.
110</file>
111
112<file name="LHAFortran">
113is a header file only, for a class derived from the above LesHouches
114one, to be used for runtime interfacing to Fortran programs, such as
115PYTHIA 6.
116</file>
117
118<file name="LHAPDFInterface">
119is a header file only, with interfaces to the key LHAPDF routines,
120as needed for a runtime interface. There is a file
121<code>lhapdfdummy/LHAPDFdummy.cc</code> with matching dummy
122implementations, however. This file is used to build a separate
123<code>liblhapdfdummy</code> library, to be linked when the LHAPDF
124library is not used, so as to avoid problems with undefined references.
125</file>
126
127<file name="MiniStringFragmentation">
128performs string fragmentation in cases where the colour singlet
129subsystem mass is so small that one or at most two primary hadrons
130should be produced from it.
131</file>
132
133<file name="MultipleInteractions">
134performs multiple parton-parton interactions.
135</file>
136
137<file name="ParticleData">
138contains a database of all necessary particle data (masses, names, ..)
139and decay channels.
140</file>
141
142<file name="ParticleDecays">
143performs the decays of all normal unstable hadrons and leptons, i.e.
144in mass up to and including <ei>b bbar</ei> systems. It is not
145intended for decays of electroweak resonances, like <ei>Z^0</ei>.
146</file>
147
148<file name="PartonDistributions">
149contains parton distribution functions for the proton and electron.
150Currently very simple, with only two <ei>p</ei> parametrizations
151and one <ei>e</ei> ditto available, but it is possible to link in
152external sets.
153</file>
154
155<file name="PartonLevel">
156turns the (hard) process above into a complete set of partons, by
157adding initial- and final-state radiation, multiple parton--parton
158interactions, and beam remnants.
159</file>
160
161<file name="PhaseSpace">
162selects a point in phase space for the hard-process generation,
163optimized separately for each process to give improved Monte Carlo
164efficiency.
165</file>
166
167<file name="ProcessContainer">
168packages the information on a given subprocess, combining the
169phase-space selection and cross-section evaluation machineries
170with some statistics information. Also sets up the list of processes
171to be studied in a run.
172</file>
173
174<file name="ProcessLevel">
175handles the generation of the (hard) process that sets the character
176of the event. This involves either using internally implemented
177processes or linking to Les Houches information. The latter can
178be by runtime interfaces or by reading in a file. This step also
179includes resonance decays.
180</file>
181
182<file name="Pythia">
183is the main class, that administrates the whole event generation
184process by making use of all the others classes. Objects of most
185other classes reside (directly or indirectly) inside <code>Pythia</code>,
186so only a <code>Pythia</code> object needs to be explicitly instantiated
187and addressed by the user.
188</file>
189
190<file name="Pythia6Interface">
191is a header file only, with interfaces to the key PYTHIA 6 routines,
192as needed for a runtime Les Houches interface to this program.
193</file>
194
195<file name="PythiaComplex">
196is only a <code>.h</code> file, containing a <code>typedef</code> for
197double precision complex numbers.
198</file>
199
200<file name="PythiaStdlib">
201is only a <code>.h</code> file, containing most of the <code>Stdlib</code>
202headers used in PYTHIA 8, with <code>using</code> directives. It defines
203<code>M_PI</code> if this is not already done. Also a few simple inline
204methods: <code>pow2(x)</code>, <code>pow3(x)</code>, <code>pow4(x)</code>
205and <code>pow5(x)</code> for small integer powers, and
206<code>sqrtpos(x)</code> where a <code>max(0., x)</code> ensures that one
207does not take the square root of a negative number.
208</file>
209
210<file name="ResonanceDecays">
211decays resonances as part of the hard-process stage, in many cases
212(but not all) including angular correlations between the decay products.
213</file>
214
215<file name="ResonanceWidths">
216encodes some properties of resonances, in particular the dynamic
217calculation of widths.
218</file>
219
220<file name="Settings">
221contains a database of all flags, modes, parameters and words that
222determine the performance of the generator. Initial values are obtained
223from the contents of the <code>.xml</code> files, but these values can
224then be changed by the user.
225</file>
226
227<file name="SigmaCompositeness">
228contains the cross sections and matrix elements for production of
229some particles in compositeness scenarios, specifically excited
230fermions.
231</file>
232
233<file name="SigmaEW">
234contains the cross sections and matrix elements for electroweak
235processes involving photons, <ei>Z^0</ei>'s and <ei>W^+-</ei>'s.
236</file>
237
238<file name="SigmaExtraDim">
239contains the cross sections and matrix elements for processes in
240scenarios involving extra dimensions.
241</file>
242
243<file name="SigmaHiggs">
244contains the cross sections and matrix elements for Higgs production.
245</file>
246
247<file name="SigmaLeftRightSym">
248contains the cross sections and matrix elements for particle production
249in left-right-symmetry scenarios, specifically righthanded <ei>Z</ei>
250and <ei>W</ei> bosons and doubly-charged Higgs bosons.
251</file>
252
253<file name="SigmaLeptoquark">
254contains the cross sections and matrix elements for leptoquark production.
255</file>
256
257<file name="SigmaNewGaugeBosons">
258contains the cross sections and matrix elements for a <ei>Z'^0</ei>,
259a <ei>W^+-</ei> and a horizontal gauge boson <ei>R^0</ei>.
260</file>
261
262<file name="SigmaOnia">
263contains the cross sections and matrix elements for charmonium and
264bottomonium production.
265</file>
266
267<file name="SigmaProcess">
268contains the base class and derived classes for the evaluation of
269different matrix elements. Also keeps track of allowed incoming
270parton configurations and their cross sections, including parton
271densities. In order to keep this file from becoming too big, actual
272cross sections are found in several separate files of derived classes:
273<code>SigmaQCD</code>, <code>SigmaEW</code>, <code>SigmaOnia</code>,
274<code>SigmaHiggs</code>, <code>SigmaSUSY</code>,
275<code>SigmaNewGaugeBosons</code>, <code>SigmaLeftRightSym</code>,
276<code>SigmaLeptoquark</code>, <code>SigmaCompositeness</code> and
277<code>SigmaExtraDim</code>.
278</file>
279
280<file name="SigmaQCD">
281contains the cross sections and matrix elements for soft and hard
282QCD processes.
283</file>
284
285<file name="SigmaSUSY">
286contains the cross sections and matrix elements for Supersymmetric
287processes.
288</file>
289
290<file name="SigmaTotal">
291contains parametrizations of total, elastic and diffractive hadronic
292cross sections.
293</file>
294
295<file name="SpaceShower">
296performs spacelike initial-state transverse-momentum-ordered
297shower evolution.
298</file>
299
300<file name="StandardModel">
301contains the running <ei>alpha_strong</ei>, with <ei>Lambda</ei>
302matching at flavour thresholds, the running <ei>alpha_em</ei>,
303CKM mixing matrices, and a few other parameters such as
304<ei>sin^2(theta_W)</ei>.
305</file>
306
307<file name="StringFragmentation">
308performs string fragmentation of a given set of partons.
309</file>
310
311<file name="SusyLesHouches">
312contains information on SUSY parameters and particle data as specified
313by the SUSY Les Houches Accord.
314</file>
315
316<file name="TimeShower">
317performs timelike final-state transverse-momentum-ordered
318shower evolution.
319</file>
320
321<file name="UserHooks">
322Provides a way for a user to study the event at a few intermediate
323stages of evolution, to reject the event as a whole or to modify
324its cross-section weight.
325</file>
326
327</chapter>
328
329<!-- Copyright (C) 2008 Torbjorn Sjostrand -->