[35cdc46] | 1 | //FJSTARTHEADER
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[b7b836a] | 2 | // $Id: CASubJetTagger.hh 4354 2018-04-22 07:12:37Z salam $
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[d7d2da3] | 3 | //
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[b7b836a] | 4 | // Copyright (c) 2005-2018, 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 | #ifndef __CASUBJET_TAGGER_HH__
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| 32 | #define __CASUBJET_TAGGER_HH__
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| 33 |
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| 34 | #include <fastjet/PseudoJet.hh>
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| 35 | #include <fastjet/WrappedStructure.hh>
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| 36 | #include <fastjet/tools/Transformer.hh>
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| 37 | #include "fastjet/LimitedWarning.hh"
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| 38 |
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| 39 | FASTJET_BEGIN_NAMESPACE
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| 40 |
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| 41 | class CASubJetTagger;
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| 42 | class CASubJetTaggerStructure;
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| 43 |
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| 44 | //----------------------------------------------------------------------
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| 45 | /// @ingroup tools_taggers
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| 46 | /// \class CASubJetTagger
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| 47 | /// clean (almost parameter-free) tagger searching for the element in
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| 48 | /// the clustering history that maximises a chosen distance
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| 49 | ///
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| 50 | /// class to help us get a clean (almost parameter-free) handle on
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| 51 | /// substructure inside a C/A jet. It follows the logic described in
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| 52 | /// arXiv:0906.0728 (and is inspired by the original Cambridge
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| 53 | /// algorithm paper in its use of separate angular and dimensionful
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| 54 | /// distances), but provides some extra flexibility.
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| 55 | ///
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| 56 | /// It searches for all splittings that pass a symmetry cut (zcut) and
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| 57 | /// then selects the one with the largest auxiliary scale choice
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| 58 | /// (e.g. jade distance of the splitting, kt distance of the
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| 59 | /// splitting, etc.)
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| 60 | ///
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| 61 | /// By default, the zcut is calculated from the fraction of the child
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| 62 | /// pt carried by the parent jet. If one calls set_absolute_z_cut the
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| 63 | /// fraction of transverse momentum will be computed wrt the original
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| 64 | /// jet.
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| 65 | ///
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| 66 | /// original code copyright (C) 2009 by Gavin Salam, released under
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| 67 | /// the GPL.
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| 68 | ///
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| 69 | /// \section desc Options
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| 70 | ///
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| 71 | /// - the distance choice: options are
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| 72 | /// kt2_distance : usual min(kti^2,ktj^2)DeltaR_{ij}^2
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| 73 | /// jade_distance : kti . ktj DeltaR_{ij}^2 (LI version of jade)
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| 74 | /// jade2_distance : kti . ktj DeltaR_{ij}^4 (LI version of jade * DR^2)
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| 75 | /// plain_distance : DeltaR_{ij}^2
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| 76 | /// mass_drop_distance : m_jet - max(m_parent1,m_parent2)
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| 77 | /// dot_product_distance: parent1.parent2
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| 78 | /// (kt2_distance by default)
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| 79 | ///
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| 80 | /// - the z cut (0 by default)
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| 81 | ///
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| 82 | /// - by calling set_absolute_z_cut(), one can ask that the pt
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| 83 | /// fraction if calculated wrt the original jet
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| 84 | ///
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| 85 | /// - by calling set_dr_min(drmin), one can ask that only the
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| 86 | /// recombinations where the 2 objects are (geometrically) distant
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| 87 | /// by at least drmin are kept in the maximisation.
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| 88 | ///
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| 89 | /// \section input Input conditions
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| 90 | ///
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| 91 | /// - the jet must have been obtained from a Cambridge/Aachen cluster
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| 92 | /// sequence
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| 93 | ///
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| 94 | /// \section output Output/structure
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| 95 | ///
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| 96 | /// - the element of the cluster sequence maximising the requested
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| 97 | /// distance (and satisfying the zcut) is returned.
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| 98 | ///
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| 99 | /// - if the original jet has no parents, it will be returned
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| 100 | ///
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| 101 | /// - the value of the "z" and distance corresponding to that history
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| 102 | /// element are stored and accessible through
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| 103 | /// result.structure_of<CASubJetTagger>().z();
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| 104 | /// result.structure_of<CASubJetTagger>().distance();
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| 105 | ///
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| 106 | class CASubJetTagger : public Transformer {
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| 107 | public:
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| 108 |
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| 109 | /// the available choices of auxiliary scale with respect to which
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| 110 | /// to order the splittings
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| 111 | enum ScaleChoice {
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| 112 | kt2_distance, //< usual min(kti^2,ktj^2)DeltaR_{ij}^2
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| 113 | jade_distance, //< kti . ktj DeltaR_{ij}^2 (LI version of jade)
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| 114 | jade2_distance, //< kti . ktj DeltaR_{ij}^4 (LI version of jade * DR^2)
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| 115 | plain_distance, //< DeltaR_{ij}^2
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| 116 | mass_drop_distance, //< m_jet - max(m_parent1,m_parent2)
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| 117 | dot_product_distance //< parent1.parent2
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| 118 | };
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| 119 |
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| 120 | /// just constructs
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| 121 | CASubJetTagger(ScaleChoice scale_choice = jade_distance,
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| 122 | double z_threshold = 0.1)
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| 123 | : _scale_choice(scale_choice), _z_threshold(z_threshold),
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| 124 | _dr2_min(0.0), _absolute_z_cut(false){};
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| 125 |
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| 126 | /// sets a minimum delta R below which spliting will be ignored
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| 127 | /// (only relevant if set prior to calling run())
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| 128 | void set_dr_min(double drmin) {_dr2_min = drmin*drmin;}
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| 129 |
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| 130 | /// returns a textual description of the tagger
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| 131 | virtual std::string description() const;
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| 132 |
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| 133 | /// If (abs_z_cut) is set to false (the default) then for a
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| 134 | /// splitting to be considered, each subjet must satisfy
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| 135 | ///
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| 136 | /// p_{t,sub} > z_threshold * p_{t,parent}
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| 137 | ///
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| 138 | /// whereas if it is set to true, then each subject must satisfy
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| 139 | ///
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| 140 | /// p_{t,sub} > z_threshold * p_{t,original-jet}
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| 141 | ///
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| 142 | /// where parent is the immediate parent of the splitting, and
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| 143 | /// original jet is the one supplied to the run() function.
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| 144 | ///
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| 145 | /// Only relevant is called prior to run().
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| 146 | void set_absolute_z_cut(bool abs_z_cut=true) {_absolute_z_cut = abs_z_cut;}
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| 147 |
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| 148 | /// runs the tagger on the given jet and
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| 149 | /// returns the tagged PseudoJet if successful, or a PseudoJet==0 otherwise
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| 150 | /// (standard access is through operator()).
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| 151 | virtual PseudoJet result(const PseudoJet & jet) const;
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| 152 |
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| 153 | /// the type of Structure returned
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| 154 | typedef CASubJetTaggerStructure StructureType;
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| 155 |
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| 156 | protected:
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| 157 | /// class that contains the result internally
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| 158 | class JetAux {
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| 159 | public:
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| 160 | PseudoJet jet; //< the subjet (immediate parent of splitting)
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| 161 | double aux_distance; //< the auxiliary distance between its two subjets
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| 162 | double delta_r; //< the angular distance between its two subjets
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| 163 | double z; //< the transverse momentum fraction
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| 164 | };
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| 165 |
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| 166 |
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| 167 | void _recurse_through_jet(const PseudoJet & current_jet,
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| 168 | JetAux &aux_max,
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| 169 | const PseudoJet & original_jet) const;
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| 170 |
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| 171 | ScaleChoice _scale_choice;
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| 172 | double _z_threshold;
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| 173 | double _dr2_min;
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| 174 | bool _absolute_z_cut;
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| 175 |
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| 176 | static LimitedWarning _non_ca_warnings;
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| 177 | };
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| 178 |
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| 179 |
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| 180 | //------------------------------------------------------------------------
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| 181 | /// @ingroup tools_taggers
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| 182 | /// the structure returned by a CASubJetTagger
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| 183 | ///
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| 184 | /// Since this is directly an element of the ClusterSequence, we keep
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| 185 | /// basically the original ClusterSequenceStructure (wrapped for
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| 186 | /// memory-management reasons) and add information about the pt
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| 187 | /// fraction and distance of the subjet structure
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| 188 | class CASubJetTaggerStructure : public WrappedStructure{
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| 189 | public:
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| 190 | /// default ctor
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| 191 | /// \param result_jet the jet for which we have to keep the
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| 192 | /// structure
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| 193 | CASubJetTaggerStructure(const PseudoJet & result_jet)
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| 194 | : WrappedStructure(result_jet.structure_shared_ptr()){}
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| 195 |
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| 196 | /// returns the scale choice asked for the maximisation
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| 197 | CASubJetTagger::ScaleChoice scale_choice() const {return _scale_choice;}
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| 198 |
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| 199 | /// returns the value of the distance measure (corresponding to
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| 200 | /// ScaleChoice) for this jet's splitting
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| 201 | double distance() const {return _distance;}
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| 202 |
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| 203 | /// returns the pt fraction contained by the softer of the two component
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| 204 | /// pieces of this jet (normalised relative to this jet)
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| 205 | double z() const {return _z;}
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| 206 |
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| 207 | /// returns the pt fraction contained by the softer of the two component
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| 208 | /// pieces of this jet (normalised relative to the original jet)
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| 209 | bool absolute_z() const {return _absolute_z;}
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| 210 |
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| 211 | // /// returns the original jet (before tagging)
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| 212 | // const PseudoJet & original() const {return _original_jet;}
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| 213 |
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| 214 | protected:
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| 215 | CASubJetTagger::ScaleChoice _scale_choice; ///< the user scale choice
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| 216 | double _distance; ///< the maximal distance associated with the result
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| 217 | bool _absolute_z; ///< whether z is computed wrt to the original jet or not
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| 218 | double _z; ///< the transverse momentum fraction
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| 219 | // PseudoJet _original_jet; ///< the original jet (before tagging)
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| 220 |
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| 221 | friend class CASubJetTagger; ///< to allow setting the internal information
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| 222 | };
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| 223 |
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| 224 | FASTJET_END_NAMESPACE
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| 225 |
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| 226 | #endif // __CASUBJET_HH__
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