[d7d2da3] | 1 | //STARTHEADER
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| 2 | // $Id: MassDropTagger.hh 2731 2011-11-21 12:15:21Z soyez $
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| 3 | //
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| 4 | // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
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| 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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| 15 | // development and are described in hep-ph/0512210. If you use
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| 16 | // FastJet as part of work towards a scientific publication, please
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| 17 | // include a citation to the FastJet paper.
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| 18 | //
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| 19 | // FastJet is distributed in the hope that it will be useful,
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| 20 | // but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 21 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 22 | // GNU General Public License for more details.
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| 23 | //
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| 24 | // You should have received a copy of the GNU General Public License
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| 25 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>.
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| 26 | //----------------------------------------------------------------------
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| 27 | //ENDHEADER
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| 28 |
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| 29 | #ifndef __FASTJET_MASS_DROP_TAGGER_HH__
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| 30 | #define __FASTJET_MASS_DROP_TAGGER_HH__
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| 31 |
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| 32 | #include <fastjet/tools/Transformer.hh>
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| 33 | #include <fastjet/LimitedWarning.hh>
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| 34 | #include <fastjet/WrappedStructure.hh>
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| 35 |
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| 36 | FASTJET_BEGIN_NAMESPACE
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| 37 |
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| 38 | class MassDropTagger;
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| 39 | class MassDropTaggerStructure;
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| 40 |
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| 41 | //----------------------------------------------------------------------
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| 42 | /// @ingroup tools_taggers
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| 43 | /// \class MassDropTagger
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| 44 | /// Class that helps perform 2-pronged boosted tagging using
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| 45 | /// the "mass-drop" technique (with asymmetry cut) introduced by Jonathan
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| 46 | /// Butterworth, Adam Davison, Mathieu Rubin and Gavin Salam in
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| 47 | /// arXiv:0802.2470 in the context of a boosted Higgs search.
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| 48 | ///
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| 49 | /// The tagger proceeds as follows:
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| 50 | ///
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| 51 | /// 0. start from a jet obtained from with the Cambridge/Aachen
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| 52 | /// algorithm
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| 53 | ///
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| 54 | /// 1. undo the last step of the clustering step j -> j1 + j2 (label
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| 55 | /// them such as j1 is the most massive).
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| 56 | ///
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| 57 | /// 2. if there is a mass drop, i.e. m_j1/m_j < mu_cut, and the
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| 58 | /// splitting is sufficiently symmetric, \f${\rm
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| 59 | /// min}(p_{tj1}^2,p_{tj2}^2)\Delta R_{j1,j2}^2 > y_{\rm cut}
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| 60 | /// m_j^2\f$, keep j as the result of the tagger (with j1 and j2
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| 61 | /// its 2 subjets)
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| 62 | ///
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| 63 | /// 3. otherwise, redefine j to be equal to j1 and return to step 1.
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| 64 | ///
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| 65 | /// Note that in the original proposal, j1 and j2 are both required
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| 66 | /// to be b-tagged and a filter (with Rfilt=min(0.3,Rbb/2) and
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| 67 | /// n_filt=3) is also applied to j to obtain the final "Higgs candidate".
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| 68 | /// See the example \subpage Example12 for details.
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| 69 | ///
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| 70 | /// \section desc Options
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| 71 | ///
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| 72 | /// The constructor has the following arguments:
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| 73 | /// - The first argument is the minimal mass drop that is required (mu_cut) [0.67
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| 74 | /// by default]
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| 75 | /// - The second argument is the asymmetry cut (y_cut) [0.09 by default]
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| 76 | ///
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| 77 | /// \section input Input conditions
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| 78 | ///
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| 79 | /// - one must be able to successively "uncluster" the original jet
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| 80 | /// using "has_parents"
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| 81 | ///
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| 82 | /// \section output Output/structure
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| 83 | ///
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| 84 | /// - the 2 subjets are kept as pieces if some substructure is found,
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| 85 | /// otherwise a single 0-momentum piece is returned
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| 86 | /// - the 'mu' and 'y' values corresponding to the unclustering step
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| 87 | /// that passed the tagger's cuts
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| 88 | ///
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| 89 | /// See also \subpage Example12 for a usage example.
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| 90 | class MassDropTagger : public Transformer{
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| 91 | public:
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| 92 | /// default ctor
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| 93 | MassDropTagger(const double mu=0.67, const double ycut=0.09) : _mu(mu), _ycut(ycut){};
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| 94 |
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| 95 | /// returns a textual description of the tagger
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| 96 | virtual std::string description() const;
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| 97 |
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| 98 | /// runs the tagger on the given jet and
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| 99 | /// returns the tagged PseudoJet if successful, a PseudoJet==0 otherwise
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| 100 | /// (standard access is through operator()).
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| 101 | /// \param jet the PseudoJet to tag
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| 102 | virtual PseudoJet result(const PseudoJet & jet) const;
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| 103 |
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| 104 | /// the type of the associated structure
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| 105 | typedef MassDropTaggerStructure StructureType;
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| 106 |
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| 107 | protected:
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| 108 | double _mu, _ycut;
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| 109 | static LimitedWarning _warnings_nonca;
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| 110 | };
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| 111 |
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| 112 |
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| 113 | //------------------------------------------------------------------------
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| 114 | /// @ingroup tools_taggers
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| 115 | /// \class MassDropTaggerStructure
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| 116 | /// the structure returned by the MassDropTagger transformer.
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| 117 | ///
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| 118 | /// See the MassDropTagger class description for the details of what
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| 119 | /// is inside this structure
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| 120 | ///
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| 121 | class MassDropTaggerStructure : public WrappedStructure{
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| 122 | public:
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| 123 | /// ctor with initialisation
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| 124 | /// \param pieces the pieces of the created jet
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| 125 | /// \param rec the recombiner from the underlying cluster sequence
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| 126 | MassDropTaggerStructure(const PseudoJet & result_jet) :
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| 127 | WrappedStructure(result_jet.structure_shared_ptr()), _mu(0.0), _y(0.0){}
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| 128 |
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| 129 | /// returns the mass-drop ratio, pieces[0].m()/jet.m(), for the splitting
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| 130 | /// that triggered the mass-drop condition
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| 131 | inline double mu() const{return _mu;}
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| 132 |
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| 133 | /// returns the value of y = (squared kt distance) / (squared mass) for the
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| 134 | /// splitting that triggered the mass-drop condition
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| 135 | inline double y() const {return _y;}
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| 136 |
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| 137 | // /// returns the original jet (before tagging)
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| 138 | // const PseudoJet & original() const {return _original_jet;}
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| 139 |
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| 140 | protected:
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| 141 | double _mu; ///< the value of the mass-drop parameter
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| 142 | double _y; ///< the value of the asymmetry parameter
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| 143 | // PseudoJet _original_jet; ///< the original jet (before tagging)
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| 144 |
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| 145 | // allow the tagger to set these
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| 146 | friend class MassDropTagger;
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| 147 | };
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| 148 |
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| 149 |
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| 150 |
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| 151 | FASTJET_END_NAMESPACE
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| 152 |
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| 153 | #endif // __FASTJET_MASS_DROP_TAGGER_HH__
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| 154 |
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