FastJet 3.0.2
08-selector.cc
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00001 //----------------------------------------------------------------------
00002 /// \file
00003 /// \page Example08 08 - using the Selector tool
00004 ///
00005 /// fastjet sample program to illustrate the use of fastjet::Selector
00006 ///
00007 /// run it with    : ./08-selector < data/single-event.dat
00008 ///
00009 /// Source code: 08-selector.cc
00010 //----------------------------------------------------------------------
00011 
00012 //STARTHEADER
00013 // $Id: 08-selector.cc 2684 2011-11-14 07:41:44Z soyez $
00014 //
00015 // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
00016 //
00017 //----------------------------------------------------------------------
00018 // This file is part of FastJet.
00019 //
00020 //  FastJet is free software; you can redistribute it and/or modify
00021 //  it under the terms of the GNU General Public License as published by
00022 //  the Free Software Foundation; either version 2 of the License, or
00023 //  (at your option) any later version.
00024 //
00025 //  The algorithms that underlie FastJet have required considerable
00026 //  development and are described in hep-ph/0512210. If you use
00027 //  FastJet as part of work towards a scientific publication, please
00028 //  include a citation to the FastJet paper.
00029 //
00030 //  FastJet is distributed in the hope that it will be useful,
00031 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
00032 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00033 //  GNU General Public License for more details.
00034 //
00035 //  You should have received a copy of the GNU General Public License
00036 //  along with FastJet. If not, see <http://www.gnu.org/licenses/>.
00037 //----------------------------------------------------------------------
00038 //ENDHEADER
00039 
00040 #include "fastjet/ClusterSequence.hh"
00041 #include "fastjet/Selector.hh" 
00042 #include <iostream> // needed for io
00043 #include <cstdio>   // needed for io
00044 
00045 using namespace std;
00046 using namespace fastjet;
00047 
00048 int main(){
00049   
00050   // read in input particles
00051   //----------------------------------------------------------
00052   vector<PseudoJet> input_particles;
00053   
00054   double px, py , pz, E;
00055   while (cin >> px >> py >> pz >> E) {
00056     // create a PseudoJet with these components and put it onto
00057     // the back of the input_particles vector
00058     input_particles.push_back(PseudoJet(px,py,pz,E)); 
00059   }
00060 
00061   // Selector application #1: keep particles within a given acceptance
00062   // e.g. all particles with 1<|y|<2.5, and all particles with pt>1 for |y|<1
00063   // (we include the (redundant) fastjet:: prefix just as a reminder that this
00064   // is the namespace where Selector is to be found).
00065   //----------------------------------------------------------
00066   fastjet::Selector particle_selector = fastjet::SelectorAbsRapRange(1.0,2.5)
00067     || (fastjet::SelectorAbsRapMax(1.0) && fastjet::SelectorPtMin(1.0));
00068   cout << input_particles.size() << " particles before selector" << endl;
00069   input_particles = particle_selector(input_particles);
00070   cout << input_particles.size() << " particles after selector" << endl;
00071 
00072   // create a jet definition: 
00073   // a jet algorithm with a given radius parameter
00074   //----------------------------------------------------------
00075   double R = 0.6;
00076   JetDefinition jet_def(kt_algorithm, R);
00077 
00078 
00079   // run the jet clustering with the above jet definition
00080   //----------------------------------------------------------
00081   ClusterSequence clust_seq(input_particles, jet_def);
00082 
00083 
00084   // get the 5 hardest jets within |y|<2 
00085   //
00086   // Note that this nicely illustrates that you should watch out that
00087   // Selectors do not necessarily commute.
00088   //
00089   // The && operator behaves like a logical and, i.e. it keeps objects
00090   // that satisfy both criteria (independently). It does commute.
00091   //
00092   // The * operator applies Selectors successively (starting from the
00093   // rightmost one as in a usual operator product). Here, order may matter.
00094   //----------------------------------------------------------
00095   Selector jet_selector = SelectorNHardest(5) * SelectorAbsRapMax(2.0);
00096   vector<PseudoJet> inclusive_jets = sorted_by_pt(jet_selector(clust_seq.inclusive_jets()));
00097 
00098 
00099   // tell the user what was done
00100   //  - the description of the algorithm used
00101   //  - the description of teh selectors used
00102   //  - the jets
00103   //    show the output as 
00104   //      {index, rap, phi, pt}
00105   //----------------------------------------------------------
00106   double rapmin, rapmax;
00107 
00108   cout << "Ran " << jet_def.description() << endl;
00109 
00110   cout << "Selected particles: " << particle_selector.description() << endl;
00111   particle_selector.get_rapidity_extent(rapmin, rapmax);
00112   cout << "  with a total rapidity range of [" << rapmin << ", " << rapmax << "]" << endl;
00113 
00114   cout << "Selected jets: " << jet_selector.description() << endl;
00115   jet_selector.get_rapidity_extent(rapmin, rapmax);
00116   cout << "  with a total rapidity range of [" << rapmin << ", " << rapmax << "]" << endl;
00117 
00118   // label the columns
00119   printf("%5s %15s %15s %15s\n","jet #", "rapidity", "phi", "pt");
00120  
00121   // print out the details for each jet
00122   for (unsigned int i = 0; i < inclusive_jets.size(); i++) {
00123     printf("%5u %15.8f %15.8f %15.8f\n",
00124            i, inclusive_jets[i].rap(), inclusive_jets[i].phi(),
00125            inclusive_jets[i].perp());
00126   }
00127 
00128   return 0;
00129 }
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