[d7d2da3] | 1 | #ifndef __FASTJET_RESTFRAMENSUBJETTINESS_TAGGER_HH__
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| 2 | #define __FASTJET_RESTFRAMENSUBJETTINESS_TAGGER_HH__
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| 3 |
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[35cdc46] | 4 | //FJSTARTHEADER
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[cb80e6f] | 5 | // $Id: RestFrameNSubjettinessTagger.hh 4442 2020-05-05 07:50:11Z soyez $
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[d7d2da3] | 6 | //
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[cb80e6f] | 7 | // Copyright (c) 2005-2020, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
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[d7d2da3] | 8 | //
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| 9 | //----------------------------------------------------------------------
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| 10 | // This file is part of FastJet.
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| 11 | //
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| 12 | // FastJet is free software; you can redistribute it and/or modify
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| 13 | // it under the terms of the GNU General Public License as published by
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| 14 | // the Free Software Foundation; either version 2 of the License, or
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| 15 | // (at your option) any later version.
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| 16 | //
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| 17 | // The algorithms that underlie FastJet have required considerable
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[35cdc46] | 18 | // development. They are described in the original FastJet paper,
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| 19 | // hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use
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[d7d2da3] | 20 | // FastJet as part of work towards a scientific publication, please
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[35cdc46] | 21 | // quote the version you use and include a citation to the manual and
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| 22 | // optionally also to hep-ph/0512210.
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[d7d2da3] | 23 | //
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| 24 | // FastJet is distributed in the hope that it will be useful,
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| 25 | // but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 26 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 27 | // GNU General Public License for more details.
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| 28 | //
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| 29 | // You should have received a copy of the GNU General Public License
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| 30 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>.
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| 31 | //----------------------------------------------------------------------
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[35cdc46] | 32 | //FJENDHEADER
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[d7d2da3] | 33 |
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| 34 | #include <fastjet/PseudoJet.hh>
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| 35 | #include <fastjet/JetDefinition.hh>
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| 36 | #include <fastjet/CompositeJetStructure.hh>
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| 37 | #include <fastjet/tools/Transformer.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 RestFrameNSubjettinessTagger;
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| 42 | class RestFrameNSubjettinessTaggerStructure;
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| 43 |
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| 44 | //----------------------------------------------------------------------
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| 45 | /// @ingroup tools_taggers
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| 46 | /// \class RestFrameNSubjettinessTagger
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| 47 | /// Class that helps perform 2-pronged boosted tagging using
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| 48 | /// a reclustering in the jet's rest frame, supplemented with a cut on N-subjettiness
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| 49 | /// (and a decay angle), as discussed by Ji-Hun Kim in arXiv:1011.1493.
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| 50 | ///
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| 51 | /// To tag a fat jet, the tagger proceeds as follows:
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| 52 | ///
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| 53 | /// - boost its constituents into the rest frame of the jet
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| 54 | ///
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| 55 | /// - recluster them using another jet definition (the original
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| 56 | /// choice was SISCone in spherical coordinates with R=0.6 and
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| 57 | /// f=0.75.
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| 58 | ///
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| 59 | /// - keep the 2 most energetic subjets (\f$q_{1,2}\f$) and compute
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| 60 | /// the 2-subjettiness
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| 61 | /// \f[
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| 62 | /// \tau_2^j = \frac{2}{m_{\rm jet}^2}\,
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| 63 | /// \sum_{k\in {\rm jet}} {\rm min}(q_1.p_k,q_2.p_k)
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| 64 | /// \f]
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| 65 | /// where the sum runs over the constituents of the jet.
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| 66 | ///
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| 67 | /// - require \f$\tau_2^j < \tau_2^{\rm cut}\f$ [0.08 by default]
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| 68 | ///
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| 69 | /// - impose that (in the rest frame of the fat jet), the angles
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| 70 | /// between the 2 most energetic subjets and the boost axis are
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| 71 | /// both large enough: \f$\cos(\theta_s)<c_\theta^{\rm cut}\f$
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| 72 | /// [0.8 by default]
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| 73 | ///
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| 74 | /// Note that in the original version, the jets to be tagged were reconstructed
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| 75 | /// using SISCone with R=0.8 and f=0.75. Also, b-tagging was imposed
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| 76 | /// on the 2 subjets found in the rest-frame tagging procedure.
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| 77 | ///
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| 78 | /// \section desc Options
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| 79 | ///
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| 80 | /// The constructor has the following arguments:
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| 81 | /// - The first argument is the jet definition to be used to
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| 82 | /// recluster the constituents of the jet to be filtered (in the
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| 83 | /// rest frame of the tagged jet).
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| 84 | /// - The second argument is the cut on tau_2 [0.08 by default]
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| 85 | /// - The 3rd argument is the cut on cos(theta_s) [0.8 by default]
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| 86 | /// - If the 4th argument is true, 2 exclusive rest-frame jets will
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| 87 | /// be considered in place of the 2 most energetic inclusive jets
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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 original jet must have constituents
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| 92 | ///
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| 93 | /// \section output Output/structure
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| 94 | ///
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| 95 | /// - the 2 subjets are kept as pieces if some substructure is found,
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| 96 | /// otherwise a single 0-momentum piece
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| 97 | /// - the tau2 and maximal cos(theta_s) values computed during the
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| 98 | /// tagging can be obtained via the resulting jet's structure_of<...>()
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| 99 | /// function
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| 100 | ///
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| 101 | class RestFrameNSubjettinessTagger : public Transformer{
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| 102 | public:
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| 103 | /// ctor with arguments (see the class description above)
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| 104 | RestFrameNSubjettinessTagger(const JetDefinition subjet_def,
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| 105 | const double tau2cut=0.08,
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| 106 | const double costhetascut=0.8,
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| 107 | const bool use_exclusive = false)
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| 108 | : _subjet_def(subjet_def), _t2cut(tau2cut), _costscut(costhetascut),
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| 109 | _use_exclusive(use_exclusive){};
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| 110 |
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| 111 | /// returns a textual description of the tagger
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| 112 | virtual std::string description() const;
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| 113 |
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| 114 | /// runs the tagger on the given jet and
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| 115 | /// returns the tagged PseudoJet if successful, a PseudoJet==0 otherwise
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| 116 | /// (standard access is through operator()).
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| 117 | virtual PseudoJet result(const PseudoJet & jet) const;
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| 118 |
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| 119 | /// the type of Structure returned
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| 120 | typedef RestFrameNSubjettinessTaggerStructure StructureType;
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| 121 |
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| 122 | protected:
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| 123 | JetDefinition _subjet_def;
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| 124 | double _t2cut, _costscut;
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| 125 | bool _use_exclusive;
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| 126 | };
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| 127 |
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| 128 |
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| 129 | //------------------------------------------------------------------------
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| 130 | /// @ingroup tools_taggers
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| 131 | /// \class RestFrameNSubjettinessTaggerStructure
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| 132 | /// the structure returned by the RestFrameNSubjettinessTagger transformer.
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| 133 | ///
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| 134 | /// See the RestFrameNSubjettinessTagger class description for the details of
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| 135 | /// what is inside this structure
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| 136 | ///
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| 137 | class RestFrameNSubjettinessTaggerStructure : public CompositeJetStructure{
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| 138 | public:
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| 139 | /// ctor with pieces initialisation
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| 140 | RestFrameNSubjettinessTaggerStructure(const std::vector<PseudoJet> & pieces_in) :
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| 141 | CompositeJetStructure(pieces_in), _tau2(0.0), _costhetas(1.0){}
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| 142 |
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| 143 | /// returns the associated N-subjettiness
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| 144 | inline double tau2() const{return _tau2;}
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| 145 |
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| 146 | /// returns the associated angle with the boosted axis
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| 147 | inline double costhetas() const {return _costhetas;}
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| 148 |
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| 149 | // /// returns the original jet (before tagging)
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| 150 | // const PseudoJet & original() const {return _original_jet;}
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| 151 |
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| 152 | protected:
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| 153 | double _tau2; ///< the value of the N-subjettiness
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| 154 | double _costhetas; ///< the minimal angle between the dijets
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| 155 | ///< and the boost axis
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| 156 | // PseudoJet _original_jet; ///< the original jet (before tagging)
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| 157 |
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| 158 | // allow the tagger to set these
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| 159 | friend class RestFrameNSubjettinessTagger;
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| 160 | };
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| 161 |
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| 162 | FASTJET_END_NAMESPACE
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| 163 | #endif // __FASTJET_RESTFRAMENSUBJETTINESS_TAGGER_HH__
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| 164 |
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