FastJet 3.0.2
PxConePlugin.hh
00001 //STARTHEADER
00002 // $Id: PxConePlugin.hh 2758 2011-11-24 08:31:58Z soyez $
00003 //
00004 // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
00005 //
00006 //----------------------------------------------------------------------
00007 // This file is part of FastJet.
00008 //
00009 //  FastJet is free software; you can redistribute it and/or modify
00010 //  it under the terms of the GNU General Public License as published by
00011 //  the Free Software Foundation; either version 2 of the License, or
00012 //  (at your option) any later version.
00013 //
00014 //  The algorithms that underlie FastJet have required considerable
00015 //  development and are described in hep-ph/0512210. If you use
00016 //  FastJet as part of work towards a scientific publication, please
00017 //  include a citation to the FastJet paper.
00018 //
00019 //  FastJet is distributed in the hope that it will be useful,
00020 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
00021 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00022 //  GNU General Public License for more details.
00023 //
00024 //  You should have received a copy of the GNU General Public License
00025 //  along with FastJet. If not, see <http://www.gnu.org/licenses/>.
00026 //----------------------------------------------------------------------
00027 //ENDHEADER
00028 
00029 #ifndef __PXCONEPLUGIN_HH__
00030 #define __PXCONEPLUGIN_HH__
00031 
00032 #include "fastjet/JetDefinition.hh"
00033 
00034 // questionable whether this should be in fastjet namespace or not...
00035 
00036 FASTJET_BEGIN_NAMESPACE      // defined in fastjet/internal/base.hh
00037 
00038 //----------------------------------------------------------------------
00039 //
00040 /// @ingroup plugins
00041 /// \class PxConePlugin
00042 /// Implementation of the PxCone algorithm (plugin for fastjet v2.1 upwards)
00043 ///
00044 /// PxConePlugin is a plugin for fastjet (v2.1 upwards) that provides
00045 /// an interface to the fortran pxcone iterative cone algorithm with
00046 /// midpoint seeds.
00047 ///
00048 /// Pxcone was written by Luis del Pozo and Michael H. Seymour. It is
00049 /// not a "supported" program, so if you encounter problems, you are
00050 /// on your own...
00051 ///
00052 /// Note that pxcone sometimes encounters non-stable iterations; in
00053 /// such cases it returns an error -- the plugin propagates this by
00054 /// throwing a fastjet::Error exception; if the user wishes to have
00055 /// robust code, they should catch this exception.
00056 ///
00057 /// Pxcone has a hard-coded limit (by default 4000) on the maximum
00058 /// number of particles and protojets; if the number of particles or
00059 /// protojets exceeds this, again a fastjet::Error exception will be
00060 /// thrown.
00061 ///
00062 /// The functionality of pxcone is described at 
00063 /// http://www.hep.man.ac.uk/u/wplano/ConeJet.ps
00064 //
00065 //----------------------------------------------------------------------
00066 class PxConePlugin : public JetDefinition::Plugin {
00067 public:
00068 
00069   /// constructor for the PxConePlugin, whose arguments have the
00070   /// following meaning:
00071   ///
00072   ///   - the cone_radius is as usual in cone algorithms
00073   ///
00074   ///   - stables cones (protojets) below min_jet_energy are discarded
00075   ///     before calling the splitting procedure to resolve overlaps
00076   ///     (called epslon in pxcone).
00077   ///
00078   ///   - when two protojets overlap, if
00079   ///       (overlapping_Et)/(Et_of_softer_protojet) < overlap_threshold
00080   ///     the overlapping energy is split between the two protojets;
00081   ///     otherwise the less energetic protojet is discarded. Called
00082   ///     ovlim in pxcone.
00083   ///
00084   ///   - pxcone carries out p-scheme recombination, and the resulting 
00085   ///     jets are massless; setting E_scheme_jets = true (default
00086   ///     false) doesn't change the jet composition, but the final
00087   ///     momentum sum for the jets is carried out by direct
00088   ///     four-vector addition instead of p-scheme recombination.
00089   ///
00090   PxConePlugin (double  cone_radius_in      , 
00091                 double  min_jet_energy_in = 5.0  , 
00092                 double  overlap_threshold_in = 0.5,
00093                 bool    E_scheme_jets_in = false) : 
00094     _cone_radius        (cone_radius_in      ),
00095     _min_jet_energy     (min_jet_energy_in   ),
00096     _overlap_threshold  (overlap_threshold_in),
00097     _E_scheme_jets      (E_scheme_jets_in    ) {}
00098 
00099 
00100   // some functions to return info about parameters ----------------
00101 
00102   /// the cone radius
00103   double cone_radius        () const {return _cone_radius        ;}
00104 
00105   /// minimum jet energy (protojets below this are thrown own before
00106   /// merging/splitting) -- called epslon in pxcone
00107   double min_jet_energy     () const {return _min_jet_energy     ;}
00108 
00109   /// Maximum fraction of overlap energy in a jet -- called ovlim in pxcone.
00110   double overlap_threshold  () const {return _overlap_threshold  ;}
00111 
00112   /// if true then the final jets are returned as the E-scheme recombination
00113   /// of the particle momenta (by default, pxcone returns massless jets with
00114   /// a mean phi,eta type of recombination); regardless of what is
00115   /// returned, the internal pxcone jet-finding procedure is
00116   /// unaffected.
00117   bool E_scheme_jets()         const {return _E_scheme_jets      ;}
00118 
00119 
00120   // the things that are required by base class
00121   virtual std::string description () const;
00122   virtual void run_clustering(ClusterSequence &) const;
00123   /// the plugin mechanism's standard way of accessing the jet radius
00124   virtual double R() const {return cone_radius();}
00125 
00126 private:
00127 
00128   double _cone_radius       ;
00129   double _min_jet_energy    ;
00130   double _overlap_threshold ;
00131 
00132   bool _E_scheme_jets;
00133 
00134   static bool _first_time;
00135 
00136   /// print a banner for reference to the 3rd-party code
00137   void _print_banner(std::ostream *ostr) const;
00138 };
00139 
00140 FASTJET_END_NAMESPACE      // defined in fastjet/internal/base.hh
00141 
00142 #endif // __PXCONEPLUGIN_HH__
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