1 | #ifndef __FASTJET_RESTFRAMENSUBJETTINESS_TAGGER_HH__ |
---|
2 | #define __FASTJET_RESTFRAMENSUBJETTINESS_TAGGER_HH__ |
---|
3 | |
---|
4 | //STARTHEADER |
---|
5 | // $Id: RestFrameNSubjettinessTagger.hh 2689 2011-11-14 14:51:06Z soyez $ |
---|
6 | // |
---|
7 | // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez |
---|
8 | // |
---|
9 | //---------------------------------------------------------------------- |
---|
10 | // This file is part of FastJet. |
---|
11 | // |
---|
12 | // FastJet is free software; you can redistribute it and/or modify |
---|
13 | // it under the terms of the GNU General Public License as published by |
---|
14 | // the Free Software Foundation; either version 2 of the License, or |
---|
15 | // (at your option) any later version. |
---|
16 | // |
---|
17 | // The algorithms that underlie FastJet have required considerable |
---|
18 | // development and are described in hep-ph/0512210. If you use |
---|
19 | // FastJet as part of work towards a scientific publication, please |
---|
20 | // include a citation to the FastJet paper. |
---|
21 | // |
---|
22 | // FastJet is distributed in the hope that it will be useful, |
---|
23 | // but WITHOUT ANY WARRANTY; without even the implied warranty of |
---|
24 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
---|
25 | // GNU General Public License for more details. |
---|
26 | // |
---|
27 | // You should have received a copy of the GNU General Public License |
---|
28 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>. |
---|
29 | //---------------------------------------------------------------------- |
---|
30 | //ENDHEADER |
---|
31 | |
---|
32 | #include <fastjet/PseudoJet.hh> |
---|
33 | #include <fastjet/JetDefinition.hh> |
---|
34 | #include <fastjet/CompositeJetStructure.hh> |
---|
35 | #include <fastjet/tools/Transformer.hh> |
---|
36 | |
---|
37 | FASTJET_BEGIN_NAMESPACE |
---|
38 | |
---|
39 | class RestFrameNSubjettinessTagger; |
---|
40 | class RestFrameNSubjettinessTaggerStructure; |
---|
41 | |
---|
42 | //---------------------------------------------------------------------- |
---|
43 | /// @ingroup tools_taggers |
---|
44 | /// \class RestFrameNSubjettinessTagger |
---|
45 | /// Class that helps perform 2-pronged boosted tagging using |
---|
46 | /// a reclustering in the jet's rest frame, supplemented with a cut on N-subjettiness |
---|
47 | /// (and a decay angle), as discussed by Ji-Hun Kim in arXiv:1011.1493. |
---|
48 | /// |
---|
49 | /// To tag a fat jet, the tagger proceeds as follows: |
---|
50 | /// |
---|
51 | /// - boost its constituents into the rest frame of the jet |
---|
52 | /// |
---|
53 | /// - recluster them using another jet definition (the original |
---|
54 | /// choice was SISCone in spherical coordinates with R=0.6 and |
---|
55 | /// f=0.75. |
---|
56 | /// |
---|
57 | /// - keep the 2 most energetic subjets (\f$q_{1,2}\f$) and compute |
---|
58 | /// the 2-subjettiness |
---|
59 | /// \f[ |
---|
60 | /// \tau_2^j = \frac{2}{m_{\rm jet}^2}\, |
---|
61 | /// \sum_{k\in {\rm jet}} {\rm min}(q_1.p_k,q_2.p_k) |
---|
62 | /// \f] |
---|
63 | /// where the sum runs over the constituents of the jet. |
---|
64 | /// |
---|
65 | /// - require \f$\tau_2^j < \tau_2^{\rm cut}\f$ [0.08 by default] |
---|
66 | /// |
---|
67 | /// - impose that (in the rest frame of the fat jet), the angles |
---|
68 | /// between the 2 most energetic subjets and the boost axis are |
---|
69 | /// both large enough: \f$\cos(\theta_s)<c_\theta^{\rm cut}\f$ |
---|
70 | /// [0.8 by default] |
---|
71 | /// |
---|
72 | /// Note that in the original version, the jets to be tagged were reconstructed |
---|
73 | /// using SISCone with R=0.8 and f=0.75. Also, b-tagging was imposed |
---|
74 | /// on the 2 subjets found in the rest-frame tagging procedure. |
---|
75 | /// |
---|
76 | /// \section desc Options |
---|
77 | /// |
---|
78 | /// The constructor has the following arguments: |
---|
79 | /// - The first argument is the jet definition to be used to |
---|
80 | /// recluster the constituents of the jet to be filtered (in the |
---|
81 | /// rest frame of the tagged jet). |
---|
82 | /// - The second argument is the cut on tau_2 [0.08 by default] |
---|
83 | /// - The 3rd argument is the cut on cos(theta_s) [0.8 by default] |
---|
84 | /// - If the 4th argument is true, 2 exclusive rest-frame jets will |
---|
85 | /// be considered in place of the 2 most energetic inclusive jets |
---|
86 | /// |
---|
87 | /// \section input Input conditions |
---|
88 | /// |
---|
89 | /// - the original jet must have constituents |
---|
90 | /// |
---|
91 | /// \section output Output/structure |
---|
92 | /// |
---|
93 | /// - the 2 subjets are kept as pieces if some substructure is found, |
---|
94 | /// otherwise a single 0-momentum piece |
---|
95 | /// - the tau2 and maximal cos(theta_s) values computed during the |
---|
96 | /// tagging can be obtained via the resulting jet's structure_of<...>() |
---|
97 | /// function |
---|
98 | /// |
---|
99 | class RestFrameNSubjettinessTagger : public Transformer{ |
---|
100 | public: |
---|
101 | /// ctor with arguments (see the class description above) |
---|
102 | RestFrameNSubjettinessTagger(const JetDefinition subjet_def, |
---|
103 | const double tau2cut=0.08, |
---|
104 | const double costhetascut=0.8, |
---|
105 | const bool use_exclusive = false) |
---|
106 | : _subjet_def(subjet_def), _t2cut(tau2cut), _costscut(costhetascut), |
---|
107 | _use_exclusive(use_exclusive){}; |
---|
108 | |
---|
109 | /// returns a textual description of the tagger |
---|
110 | virtual std::string description() const; |
---|
111 | |
---|
112 | /// runs the tagger on the given jet and |
---|
113 | /// returns the tagged PseudoJet if successful, a PseudoJet==0 otherwise |
---|
114 | /// (standard access is through operator()). |
---|
115 | virtual PseudoJet result(const PseudoJet & jet) const; |
---|
116 | |
---|
117 | /// the type of Structure returned |
---|
118 | typedef RestFrameNSubjettinessTaggerStructure StructureType; |
---|
119 | |
---|
120 | protected: |
---|
121 | JetDefinition _subjet_def; |
---|
122 | double _t2cut, _costscut; |
---|
123 | bool _use_exclusive; |
---|
124 | }; |
---|
125 | |
---|
126 | |
---|
127 | //------------------------------------------------------------------------ |
---|
128 | /// @ingroup tools_taggers |
---|
129 | /// \class RestFrameNSubjettinessTaggerStructure |
---|
130 | /// the structure returned by the RestFrameNSubjettinessTagger transformer. |
---|
131 | /// |
---|
132 | /// See the RestFrameNSubjettinessTagger class description for the details of |
---|
133 | /// what is inside this structure |
---|
134 | /// |
---|
135 | class RestFrameNSubjettinessTaggerStructure : public CompositeJetStructure{ |
---|
136 | public: |
---|
137 | /// ctor with pieces initialisation |
---|
138 | RestFrameNSubjettinessTaggerStructure(const std::vector<PseudoJet> & pieces_in) : |
---|
139 | CompositeJetStructure(pieces_in), _tau2(0.0), _costhetas(1.0){} |
---|
140 | |
---|
141 | /// returns the associated N-subjettiness |
---|
142 | inline double tau2() const{return _tau2;} |
---|
143 | |
---|
144 | /// returns the associated angle with the boosted axis |
---|
145 | inline double costhetas() const {return _costhetas;} |
---|
146 | |
---|
147 | // /// returns the original jet (before tagging) |
---|
148 | // const PseudoJet & original() const {return _original_jet;} |
---|
149 | |
---|
150 | protected: |
---|
151 | double _tau2; ///< the value of the N-subjettiness |
---|
152 | double _costhetas; ///< the minimal angle between the dijets |
---|
153 | ///< and the boost axis |
---|
154 | // PseudoJet _original_jet; ///< the original jet (before tagging) |
---|
155 | |
---|
156 | // allow the tagger to set these |
---|
157 | friend class RestFrameNSubjettinessTagger; |
---|
158 | }; |
---|
159 | |
---|
160 | FASTJET_END_NAMESPACE |
---|
161 | #endif // __FASTJET_RESTFRAMENSUBJETTINESS_TAGGER_HH__ |
---|
162 | |
---|