[35cdc46] | 1 | //FJSTARTHEADER
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| 2 | // $Id: CASubJetTagger.cc 3433 2014-07-23 08:17:03Z salam $
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[d7d2da3] | 3 | //
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[35cdc46] | 4 | // Copyright (c) 2005-2014, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
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[d7d2da3] | 5 | //
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| 6 | //----------------------------------------------------------------------
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| 7 | // This file is part of FastJet.
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| 8 | //
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| 9 | // FastJet is free software; you can redistribute it and/or modify
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| 10 | // it under the terms of the GNU General Public License as published by
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| 11 | // the Free Software Foundation; either version 2 of the License, or
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| 12 | // (at your option) any later version.
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| 13 | //
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| 14 | // The algorithms that underlie FastJet have required considerable
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[35cdc46] | 15 | // development. They are described in the original FastJet paper,
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| 16 | // hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use
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[d7d2da3] | 17 | // FastJet as part of work towards a scientific publication, please
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[35cdc46] | 18 | // quote the version you use and include a citation to the manual and
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| 19 | // optionally also to hep-ph/0512210.
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[d7d2da3] | 20 | //
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| 21 | // FastJet is distributed in the hope that it will be useful,
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| 22 | // but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 23 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 24 | // GNU General Public License for more details.
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| 25 | //
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| 26 | // You should have received a copy of the GNU General Public License
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| 27 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>.
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| 28 | //----------------------------------------------------------------------
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[35cdc46] | 29 | //FJENDHEADER
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[d7d2da3] | 30 |
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| 31 | #include <fastjet/tools/CASubJetTagger.hh>
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| 32 | #include <fastjet/ClusterSequence.hh>
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| 33 |
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| 34 | #include <algorithm>
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| 35 | #include <cmath>
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| 36 | #include <sstream>
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| 37 |
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| 38 | using namespace std;
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| 39 |
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| 40 | FASTJET_BEGIN_NAMESPACE
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| 41 |
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| 42 |
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| 43 | LimitedWarning CASubJetTagger::_non_ca_warnings;
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| 44 |
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| 45 | // the tagger's description
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| 46 | //----------------------------------------------------------------------
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| 47 | string CASubJetTagger::description() const{
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| 48 | ostringstream oss;
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| 49 | oss << "CASubJetTagger with z_threshold=" << _z_threshold ;
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| 50 | if (_absolute_z_cut) oss << " (defined wrt original jet)";
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| 51 | oss << " and scale choice ";
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| 52 | switch (_scale_choice) {
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| 53 | case kt2_distance: oss << "kt2_distance"; break;
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| 54 | case jade_distance: oss << "jade_distance"; break;
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| 55 | case jade2_distance: oss << "jade2_distance"; break;
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| 56 | case plain_distance: oss << "plain_distance"; break;
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| 57 | case mass_drop_distance: oss << "mass_drop_distance"; break;
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| 58 | case dot_product_distance: oss << "dot_product_distance"; break;
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| 59 | default:
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| 60 | throw Error("unrecognized scale choice");
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| 61 | }
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| 62 |
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| 63 | return oss.str();
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| 64 | }
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| 65 |
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| 66 | // run the tagger on the given cs/jet
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| 67 | // returns the tagged PseudoJet if successful, 0 otherwise
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| 68 | //----------------------------------------------------------------------
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| 69 | PseudoJet CASubJetTagger::result(const PseudoJet & jet) const{
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| 70 | // make sure that the jet results from a Cambridge/Aachen clustering
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| 71 | if (jet.validated_cs()->jet_def().jet_algorithm() != cambridge_algorithm)
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| 72 | _non_ca_warnings.warn("CASubJetTagger should only be applied on jets from a Cambridge/Aachen clustering; use it with other algorithms at your own risk");
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| 73 |
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| 74 | // recurse in the jet to find the max distance
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| 75 | JetAux aux;
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| 76 | aux.jet = PseudoJet();
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| 77 | aux.aux_distance = -numeric_limits<double>::max();
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| 78 | aux.delta_r = 0.0;
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| 79 | aux.z = 1.0;
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| 80 | _recurse_through_jet(jet, aux, jet); // last arg remains original jet
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| 81 |
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| 82 | // create the result and its associated structure
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| 83 | PseudoJet result_local = aux.jet;
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| 84 |
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| 85 | // the tagger is considered to have failed if aux has never been set
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| 86 | // (in which case it will not have parents).
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| 87 | if (result_local == PseudoJet()) return result_local;
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| 88 |
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| 89 | // otherwise sort out the structure
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| 90 | CASubJetTaggerStructure * s = new CASubJetTaggerStructure(result_local);
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| 91 | // s->_original_jet = jet;
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| 92 | s->_scale_choice = _scale_choice;
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| 93 | s->_distance = aux.aux_distance;
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| 94 | s->_absolute_z = _absolute_z_cut;
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| 95 | s->_z = aux.z;
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| 96 |
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| 97 | result_local.set_structure_shared_ptr(SharedPtr<PseudoJetStructureBase>(s));
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| 98 |
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| 99 | return result_local;
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| 100 | }
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| 101 |
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| 102 |
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| 103 | ///----------------------------------------------------------------------
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| 104 | /// work through the jet, establishing a distance at each branching
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| 105 | inline void CASubJetTagger::_recurse_through_jet(const PseudoJet & jet, JetAux &aux, const PseudoJet & original_jet) const {
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| 106 |
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| 107 | PseudoJet parent1, parent2;
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| 108 | if (! jet.has_parents(parent1, parent2)) return;
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| 109 |
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| 110 | /// make sure the objects are not _too_ close together
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| 111 | if (parent1.squared_distance(parent2) < _dr2_min) return;
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| 112 |
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| 113 | // distance
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| 114 | double dist=0.0;
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| 115 | switch (_scale_choice) {
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| 116 | case kt2_distance:
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| 117 | // a standard (LI) kt distance
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| 118 | dist = parent1.kt_distance(parent2);
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| 119 | break;
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| 120 | case jade_distance:
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| 121 | // something a bit like a mass: pti ptj Delta R_ij^2
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| 122 | dist = parent1.perp()*parent2.perp()*parent1.squared_distance(parent2);
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| 123 | break;
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| 124 | case jade2_distance:
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| 125 | // something a bit like a mass*deltaR^2: pti ptj Delta R_ij^4
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| 126 | dist = parent1.perp()*parent2.perp()*pow(parent1.squared_distance(parent2),2);
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| 127 | break;
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| 128 | case plain_distance:
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| 129 | // Delta R_ij^2
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| 130 | dist = parent1.squared_distance(parent2);
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| 131 | break;
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| 132 | case mass_drop_distance:
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| 133 | // Delta R_ij^2
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| 134 | dist = jet.m() - std::max(parent1.m(),parent2.m());
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| 135 | break;
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| 136 | case dot_product_distance:
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| 137 | // parent1 . parent2
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| 138 | // ( = jet.m2() - parent1.m2() - parent2.m() in a
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| 139 | // 4-vector recombination scheme)
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| 140 | dist = dot_product(parent1, parent2);
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| 141 | break;
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| 142 | default:
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| 143 | throw Error("unrecognized scale choice");
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| 144 | }
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| 145 |
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| 146 | // check the z cut
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| 147 | bool zcut1 = true;
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| 148 | bool zcut2 = true;
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| 149 | double z2 = 0.0;
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| 150 |
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| 151 | // not very efficient -- sort out later
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| 152 | if (parent1.perp2() < parent2.perp2()) std::swap(parent1,parent2);
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| 153 |
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| 154 | if (_absolute_z_cut) {
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| 155 | z2 = parent2.perp() / original_jet.perp();
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| 156 | zcut1 = parent1.perp() / original_jet.perp() >= _z_threshold;
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| 157 | } else {
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| 158 | z2 = parent2.perp()/(parent1.perp()+parent2.perp());
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| 159 | }
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| 160 | zcut2 = z2 >= _z_threshold;
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| 161 |
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| 162 | if (zcut1 && zcut2){
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| 163 | if (dist > aux.aux_distance){
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| 164 | aux.jet = jet;
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| 165 | aux.aux_distance = dist;
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| 166 | aux.delta_r = sqrt(parent1.squared_distance(parent2));
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| 167 | aux.z = z2; // the softest
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| 168 | }
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| 169 | }
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| 170 |
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| 171 | if (zcut1) _recurse_through_jet(parent1, aux, original_jet);
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| 172 | if (zcut2) _recurse_through_jet(parent2, aux, original_jet);
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| 173 | }
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| 174 |
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| 175 | FASTJET_END_NAMESPACE
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