FastJet 3.0.2
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00001 //---------------------------------------------------------------------- 00002 /// \file 00003 /// \page Example06 06 - using jet areas 00004 /// 00005 /// fastjet example program for jet areas 00006 /// It mostly illustrates the usage of the 00007 /// fastjet::AreaDefinition and fastjet::ClusterSequenceArea classes 00008 /// 00009 /// run it with : ./06-area < data/single-event.dat 00010 /// 00011 /// Source code: 06-area.cc 00012 //---------------------------------------------------------------------- 00013 00014 //STARTHEADER 00015 // $Id: 06-area.cc 2684 2011-11-14 07:41:44Z soyez $ 00016 // 00017 // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez 00018 // 00019 //---------------------------------------------------------------------- 00020 // This file is part of FastJet. 00021 // 00022 // FastJet is free software; you can redistribute it and/or modify 00023 // it under the terms of the GNU General Public License as published by 00024 // the Free Software Foundation; either version 2 of the License, or 00025 // (at your option) any later version. 00026 // 00027 // The algorithms that underlie FastJet have required considerable 00028 // development and are described in hep-ph/0512210. If you use 00029 // FastJet as part of work towards a scientific publication, please 00030 // include a citation to the FastJet paper. 00031 // 00032 // FastJet is distributed in the hope that it will be useful, 00033 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00034 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00035 // GNU General Public License for more details. 00036 // 00037 // You should have received a copy of the GNU General Public License 00038 // along with FastJet. If not, see <http://www.gnu.org/licenses/>. 00039 //---------------------------------------------------------------------- 00040 //ENDHEADER 00041 00042 #include "fastjet/ClusterSequenceArea.hh" // use this instead of the "usual" ClusterSequence to get area support 00043 #include <iostream> // needed for io 00044 #include <cstdio> // needed for io 00045 00046 using namespace std; 00047 00048 /// an example program showing how to use fastjet 00049 int main(){ 00050 00051 // read in input particles 00052 //---------------------------------------------------------- 00053 vector<fastjet::PseudoJet> input_particles; 00054 00055 double px, py , pz, E; 00056 while (cin >> px >> py >> pz >> E) { 00057 // create a fastjet::PseudoJet with these components and put it onto 00058 // back of the input_particles vector 00059 input_particles.push_back(fastjet::PseudoJet(px,py,pz,E)); 00060 } 00061 00062 00063 // create a jet definition: 00064 // a jet algorithm with a given radius parameter 00065 //---------------------------------------------------------- 00066 double R = 0.6; 00067 fastjet::JetDefinition jet_def(fastjet::kt_algorithm, R); 00068 00069 00070 // Now we also need an AreaDefinition to define the properties of the 00071 // area we want 00072 // 00073 // This is made of 2 building blocks: 00074 // - the area type: 00075 // passive, active, active with explicit ghosts, or Voronoi area 00076 // - the specifications: 00077 // a VoronoiSpec or a GhostedAreaSpec for the 3 ghost-bases ones 00078 // 00079 //---------------------------------------------------------- For 00080 // GhostedAreaSpec (as below), the minimal info you have to provide 00081 // is up to what rapidity ghosts are placed. 00082 // Other commonm parameters (that mostly have an impact on the 00083 // precision on the area) include the number of repetitions 00084 // (i.e. the number of different sets of ghosts that are used) and 00085 // the ghost density (controlled through the ghost_area). 00086 // Other, more exotic, parameters (not shown here) control how ghosts 00087 // are placed. 00088 // 00089 // The ghost rapidity interval should be large enough to cover the 00090 // jets for which you want to calculate. E.g. if you want to 00091 // calculate the area of jets up to |y|=4, you need to put ghosts up 00092 // to at least 4+R (or, optionally, up to the largest particle 00093 // rapidity if this is smaller). 00094 double maxrap = 5.0; 00095 unsigned int n_repeat = 3; // default is 1 00096 double ghost_area = 0.01; // this is the default 00097 fastjet::GhostedAreaSpec area_spec(maxrap, n_repeat, ghost_area); 00098 00099 fastjet::AreaDefinition area_def(fastjet::active_area, area_spec); 00100 00101 // run the jet clustering with the above jet and area definitions 00102 // 00103 // The only change is the usage of a ClusterSequenceArea rather than 00104 //a ClusterSequence 00105 //---------------------------------------------------------- 00106 fastjet::ClusterSequenceArea clust_seq(input_particles, jet_def, area_def); 00107 00108 00109 // get the resulting jets ordered in pt 00110 //---------------------------------------------------------- 00111 double ptmin = 5.0; 00112 vector<fastjet::PseudoJet> inclusive_jets = sorted_by_pt(clust_seq.inclusive_jets(ptmin)); 00113 00114 00115 // tell the user what was done 00116 // - the description of the algorithm and area used 00117 // - extract the inclusive jets with pt > 5 GeV 00118 // show the output as 00119 // {index, rap, phi, pt, number of constituents} 00120 //---------------------------------------------------------- 00121 cout << endl; 00122 cout << "Ran " << jet_def.description() << endl; 00123 cout << "Area: " << area_def.description() << endl << endl; 00124 00125 // label the columns 00126 printf("%5s %15s %15s %15s %15s %15s\n","jet #", "rapidity", "phi", "pt", "area", "area error"); 00127 00128 // print out the details for each jet 00129 for (unsigned int i = 0; i < inclusive_jets.size(); i++) { 00130 printf("%5u %15.8f %15.8f %15.8f %15.8f %15.8f\n", i, 00131 inclusive_jets[i].rap(), inclusive_jets[i].phi(), inclusive_jets[i].perp(), 00132 inclusive_jets[i].area(), inclusive_jets[i].area_error()); 00133 } 00134 00135 return 0; 00136 }