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-<title>Sample Main Programs</title>
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-<h2>Sample Main Programs</h2>
-
-Descriptions of available classes, methods and settings are all
-very good and useful. Ultimately they are necessary for you to
-be able to fine-tune your runs to the task at hand. To get going,
-however, nothing helps like having explicit examples to study.
-This is what is provided in the <code>examples</code> subdirectory,
-along with instructions how they should be run:
-<ul>
-
-<li><code>main00.cc</code> : does not exist, but it has been defined
-in the <code>Makefile</code>, so this name could be used for a simple
-first test run.
-
-<li><code>main01.cc</code> : a simple study of the charged multiplicity
-for jet events at the LHC. (Brief example fitting on one slide.)</li>
-
-<li><code>main02.cc</code> : a simple study of the <i>pT</i> spectrum
-of Z bosons at the Tevatron. (Brief example fitting on one slide.)</li>
-
-<li><code>main03.cc</code> : a simple study of several different kinds
-of events, with the choice to be made in the <code>main03.cmnd</code>
-"cards file".</li>
-
-<li><code>main04.cc</code> : tests of cross sections, multiplicities and
-average transverse momenta for elastic, diffractive and nondiffractive
-topologies, using <code>main04.cmnd</code> to pick processes.</li>
-
-<li><code>main05.cc</code> : generation of QCD jet events at the LHC,
-with jet analysis using the <code>SlowJet</code> inclusive anti-<i>kT</i>
-sequential-recombination finder and the <code>CellJet</code>
-cone-jet finder.</li>
-
-<li><code>main06.cc</code> : generation of LEP1 hadronic events, i.e.
-<i>e^+e^- -> gamma*/Z^0 -> q qbar</i>, with charged multiplicity,
-sphericity, thrust and jet analysis.</li>
-
-<li><code>main07.cc</code> : set up a fictitious production process
-to a generic resonance, where you easily can compose your own list
-of (two-body) decay modes to a variety of final states. Also traces
-decay chains down to truly stable particles: gamma, e+-, p/pbar and
-neutrinos. Suitable for astroparticle applications, like neutralino
-pair annihilation, where cross sections are calculated separately
-in another program.</li>
-
-<li><code>main08.cc</code> : generation of the QCD jet cross section
-biased towards higher pT values, by two different techniques.
-Firstly, by splitting the run into subruns, each in its own <i>pT</i>
-bin, and adding the results properly reweighted. Two suboptions, with
-limits set either in the main program or by subrun specification in the
-<code>main08.cmnd</code> file. Secondly, by a continuous reweighting
-with a <i>pT^4</i> bias in the selection, compensated by a
-<i>1/pT^4</i> event weight. Also inclusion of soft processes is
-illustrated, with subruns and weighted events.</li>
-
-<li><code>main09.cc</code> : generation of two predetermined hard
-interactions in each event.</li>
-
-<li><code>main10.cc</code> : illustration how userHooks can be used
-interact directly with the event-generation process.</li>
-
-<li><code>main11.cc</code> : a study of top events, fed in from the
-Les Houches Event File <code>ttbar.lhe</code>, here generated by
-PYTHIA 6.4. This file currently only contains 100 events
-so as not to make the distributed PYTHIA package too big, and so serves
-mainly as a demonstration of the principles involved. </li>
-
-<li><code>main12.cc</code> : a more sophisticated variant of
-<code>main11.cc</code>, where two Les Houches Event Files
-(<code>ttbar.lhe</code> and <code>ttbar2.lhe</code>) successively
-are used as input. Also illustrating some other aspects, like the
-capability to mix in internally generated events.</li>
-
-<li><code>main13.cc</code> : a streamlined version of
-<code>main12.cc</code>, where two Les Houches Event Files
-(<code>ttbar.lhe</code> and <code>ttbar2.lhe</code>) successively
-are used as input in <code>main13.cmnd</code> file.</li>
-
-<li><code>main14.cc</code> : a systematic comparison of several
-cross section values with their corresponding values in PYTHIA 6.4,
-the latter available as a table in the code.</li>
-
-<li><code>main15.cc</code> : loop over several tries, either to redo
-B decays only or to redo the complete hadronization chain of an event.
-Since much of the generation process is only made once this is a way
-to increase efficiency.</li>
-
-<li><code>main16.cc</code> : put all user analysis code into a class
-of its own, separate from the main program; provide the "cards file"
-name as a command-line argument.</li>
-
-<li><code>main17.cc</code> : shows (a) how to use UserHooks to
-regularize onium cross section for pT -> 0, and (b) how decays
-could be handled externally.</li>
-
-<li><code>main18.cc</code> : shows how to write an event filter class,
-where you keep a vector of pointers to the subset of particles you
-want to study further. The event record itself remains unchanged.</li>
-
-<li><code>main19.cc</code> : use several instances of Pythia, one for
-signal events and others for a variable number of pileup and "beam-gas"
-events, combined into one common event record.</li>
-
-<li><code>main20.cc</code> : shows how PYTHIA 8 can write a Les Houches
-Event File, using facilities potentially useful also for other programs
-to write an LHEF.</li>
-
-<li><code>main21.cc</code> : an example how a single particle or various
-parton-level configurations can be input directly for hadronization,
-without being tied to the full process-generation machinery, e.g. to
-study the hadronization of junction topologies. Can also be used for
-single-resonance decays, with showers.</li>
-
-<li><code>main22.cc</code> : shows how an external resonance can be
-implemented as a new class derived from a PYTHIA base class, and be
-used in an external process, both of them handed in for generation
-as with normal internal classes.</li>
-
-<li><code>main23.cc</code> : shows how an external beam momentum spread
-and vertex location generator can be implemented as a new class derived
-from a PYTHIA base class, and then handed in for internal use.
-Also how to use an external random-number generator and an external
-parton distribution set.</li>
-
-<li><code>main24.cc</code> : tests of internally implemented cross sections
-for Supersymmetric particle production, with SYSY spectrum defined in
-<code>cmssm.spc</code> and settings in <code>main24.cmnd</code>. For
-illustration, an alternative example spectrum is also
-available, <code>sps1aWithDecays.spc</code>, which contains a decay
-table in SLHA format.</li>
-
-<li><code>main25.cc</code> : input RPV-SUSY events from an LHEF file that
-contains an SLHA spectrum inside its header. The event file,
-<code>main25.lhe</code>, contains a sample events that
-illustrate how to arrange color tags in the presence of the
-color-space epsilon tensors that accompany baryon number violating
-event topologies. </li>
-
-<li><code>main26.cc</code> : test program for processes in scenarios
-with large extra dimensions or unparticles. </li>
-
-<li><code>main27.cc</code> : production of Kaluza-Klein <i>gamma/Z</i>
-states in TeV-sized extra dimensions. </li>
-
-<li><code>main28.cc</code> : production of long-lived R-hadrons, that
-are forced to decay at a separate vertices and possibly with changed
-momenta.</li>
-
-<li><code>main31.cc</code> : exemplifies an improved matching of
-parton showers to LHEF-style input based on the POWHEG approach.
-The <code>main31.cmnd</code> allows to switch between several
-different matching options. It also allows to select input process,
-in this case either for the POWHEG-hvq program applied to top
-pair production [<a href="Bibliography.html" target="page">Cor10</a>] or for QCD 2+3-jet events. The small
-samples of input events are stored in the <code>powheg-hvq.lhe</code>
-and <code>powheg-dijets.lhe</code> files, respectively.
-</li>
-
-<li><code>main32.cc</code> : exemplifies MLM merging for ALPGEN events,
-see <a href="AlpgenAndMLM.html" target="page">ALPGEN and MLM merging</a> for further
-details. Traditionally the ALPGEN output is split into one file with
-events and another with parameters and cross sections (unlike in LHEF).
-Here a sample of <i>W + 3 jets</i> events is stored in
-<code>main32.unw</code> and the parameters to go with it in
-<code>main32_unw.par</code>, while normal PYTHIA control cards are in
-<code>main32.cmnd</code>.
-</li>
-
-<li><code>main41.cc</code> : similar to <code>main01</code>, except that
-the event record is output in the HepMC event record format. Requires that
-HepMC is properly linked. Note that the <code>hepmcout41.dat</code> output
-file can become quite big; so no example is included in this
-distribution.</li>
-
-<li><code>main42.cc</code> : a streamlined version for the generation
-of events that are then stored in HepMC format, without any event
-analysis. That is, all physics studies will have to be done afterwards.
-The name of the input "cards file" (e.g. <code>main42.cmnd</code>)
-and output HepMC event file (e.g. <code>hepmcout42.dat</code>) are to
-be provided as command-line arguments. Requires that HepMC is properly
-linked. Note that the HepMC output file can become quite big; so no
-example is included in this distribution.</li>
-
-<li><code>main51.cc</code> : a test of the shape of parton densities,
-as a check prior to using a given PDF set in a generator. Requires
-that LHAPDF is properly linked.</li>
-
-<li><code>main52.cc</code> : compares the charged multiplicity
-distribution, and a few other minimum-bias physics aspects, between
-default PYTHIA PDF and another one. Requires that LHAPDF is properly
-linked.</li>
-
-<li><code>main53.cc</code> : tests the possibility to do backwards
-evolution from an incoming photon at the hard interaction. Requires
-that you link to a LHAPDF set that includes the photon PDF.</li>
-
-<li><code>main61.cc</code> : a streamlined version for the generation
-of events that are then stored in HepMC format, without any event
-analysis. That is, just like <code>main42.cc</code>, with the difference
-that <code>main61.cc</code> can be used in conjunction with LHAPDF.
-The name of the input "cards file" (e.g. <code>main61.cmnd</code>)
-and output HepMC event file (e.g. <code>hepmcout61.dat</code>) are to
-be provided as command-line arguments. Requires that HepMC and LHAPDF
-are properly linked. Note that the HepMC output file can become quite
-big; so no example is included in this distribution.</li>
-
-<li><code>main62.cc</code> : a further extension of <code>main61.cc</code>,
-where subruns are used to process several consecutive LHEF,
-as in <code>main13.cc</code>, with information stored e.g in
-<code>main62.cmnd</code>. Other comments as for <code>main61.cc</code>.</li>
-
-<li><code>main71.cc</code> : an example how the FastJet jet finding
-package can be linked to allow an analysis of the final state,
-in this case for a study of W + jet production.</li>
-
-<li><code>main72.cc</code> : a comparison of SlowJet and FastJet
-jet finding, showing that they find the same jets if run under
-identical conditions, in this case for QCD jets.</li>
-
-<li><code>main81.cc</code> : do CKKW-L merging with a merging scale
-defined in <i>kT</i>. Input is provided by the <code>main81.cmnd</code>
-file and the three data files <code>w+_production_lhc_0.lhe</code>,
-<code>w+_production_lhc_1.lhe</code> and <code>w+_production_lhc_2.lhe</code>.
-</li>
-
-<li><code>main82.cc</code> : do CKKW-L merging with a user-defined
-merging scale function. Input is provided by the <code>main82.cmnd</code>
-file and the three data files <code>w+_production_lhc_0.lhe</code>,
-<code>w+_production_lhc_1.lhe</code> and <code>w+_production_lhc_2.lhe</code>.
-</li>
-
-<li><code>main83.cc</code> : as <code>main82.cc</code> but with an
-additional cut on the lowest multiplicity allowed for the reclustered
-state. The same input as for <code>main82.cc</code> can be used.
-</li>
-
-<li><code>main84.cc</code> : do CKKW-L merging with output in such a way
-that it can be used in subsequent RIVET analyses. Input is provided by
-the <code>main84.cmnd</code> file and the three data files
-<code>w+_production_lhc_0.lhe</code>, <code>w+_production_lhc_1.lhe</code>
-and <code>w+_production_lhc_2.lhe</code>.
-</li>
-
-<li><code>main91.cc</code> : exemplifies how you can link in runtime
-generation of hard processes from PYTHIA 6, using the Les Houches
-Accord facilities. This example is deprecated, since PYTHIA 8 by now
-contains essentially all hard processes found in PYTHIA 6.</li>
-
-</ul>
-
-In addition two main program illustrating the use of ROOT are available
-in the <code>rootexamples</code> subdirectory:
-
-<ul>
-
-<li><code>hist.cc</code> : shows how ROOT can be used for histogramming
-in a program that for the rest is structured like a normal PYTHIA run.
-</li>
-
-<li><code>tree.cc</code> : shows how PYTHIA events can be stored as
-ROOT trees.</li>
-
-</ul>
-
-This subdirectory also contains a special Makefile and related
-documentation.
-
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