1 | #ifndef __FASTJET_JH_TOP_TAGGER_HH__
|
---|
2 | #define __FASTJET_JH_TOP_TAGGER_HH__
|
---|
3 |
|
---|
4 | //STARTHEADER
|
---|
5 | // $Id: JHTopTagger.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 |
|
---|
33 | #include <fastjet/tools/TopTaggerBase.hh>
|
---|
34 | #include <fastjet/CompositeJetStructure.hh>
|
---|
35 | #include <fastjet/LimitedWarning.hh>
|
---|
36 |
|
---|
37 | FASTJET_BEGIN_NAMESPACE
|
---|
38 |
|
---|
39 | class JHTopTagger;
|
---|
40 | class JHTopTaggerStructure;
|
---|
41 |
|
---|
42 | //----------------------------------------------------------------------
|
---|
43 | /// @ingroup tools_taggers
|
---|
44 | /// \class JHTopTagger
|
---|
45 | /// Class that helps perform boosted top tagging using the "Johns Hopkins"
|
---|
46 | /// method from arXiv:0806.0848 (Kaplan, Rehermann, Schwartz
|
---|
47 | /// and Tweedie)
|
---|
48 | ///
|
---|
49 | ///The tagger proceeds as follows:
|
---|
50 | /// - start from a jet J obtained with the Cambridge/Aachen algorithm
|
---|
51 | /// - undo the last iteration j -> j_1,j_2 (with pt_1>pt_2) until the
|
---|
52 | /// two subjets satisfy pt_1 > delta_p pt_J (with pt_J the pt of
|
---|
53 | /// the original jet) and |y_1 - y_2| + |phi_1 - phi_2| > delta_r.
|
---|
54 | /// - if one of these criteria is not satisfied, carry on the
|
---|
55 | /// procedure with j_1 (discarding j_2)
|
---|
56 | /// - for each of the subjets found, repeat the procedure. If some
|
---|
57 | /// new substructure is found, keep these 2 new subjets, otherwise
|
---|
58 | /// keep the original subjet (found during the first iteration)
|
---|
59 | /// - at this stage, one has at most 4 subjets. If one has less than
|
---|
60 | /// 3, the tagger has failed.
|
---|
61 | /// - reconstruct the W from the 2 subjets with a mass closest to the
|
---|
62 | /// W mass
|
---|
63 | /// - impose that the W helicity angle be less than a threshold
|
---|
64 | /// cos_theta_W_max.
|
---|
65 | ///
|
---|
66 | /// \section input Input conditions
|
---|
67 | ///
|
---|
68 | /// - the original jet must have an associated (and valid)
|
---|
69 | /// ClusterSequence
|
---|
70 | /// - the tagger is designed to work with jets formed by the
|
---|
71 | /// Cambridge/Aachen (C/A) algorithm; if a non-C/A jet is passed to
|
---|
72 | /// the tagger, a warning will be issued
|
---|
73 | ///
|
---|
74 | /// \section Example
|
---|
75 | ///
|
---|
76 | /// A JHTopTagger can be used as follows:
|
---|
77 | ///
|
---|
78 | /// \code
|
---|
79 | /// double delta_p = 0.10; // subjets must carry at least this fraction of the original jet's p_t
|
---|
80 | /// double delta_r = 0.19; // subjets must be separated by at least this Manhattan distance
|
---|
81 | /// double cos_theta_W_max = 0.7; // the maximal allowed value of the W helicity angle
|
---|
82 | /// JHTopTagger top_tagger(delta_p, delta_r, cos_theta_W_max);
|
---|
83 | /// // indicate the acceptable range of top, W masses (default: no limits)
|
---|
84 | /// top_tagger.set_top_selector(SelectorMassRange(150,200));
|
---|
85 | /// top_tagger.set_W_selector (SelectorMassRange( 65, 95));
|
---|
86 | /// // now try and tag a jet
|
---|
87 | /// PseudoJet top_candidate = top_tagger(jet); // jet should come from a Cambridge/Aachen clustering
|
---|
88 | /// if (top_candidate != 0) { // successful tagging
|
---|
89 | /// double top_mass = top_candidate.m();
|
---|
90 | /// double W_mass = top_candidate.structure_of<JHTopTagger>().W().m();
|
---|
91 | /// }
|
---|
92 | /// \endcode
|
---|
93 | ///
|
---|
94 | /// The full set of information available from the structure_of<JHTopTagger>()
|
---|
95 | /// call is
|
---|
96 | ///
|
---|
97 | /// - PseudoJet W() : the W subjet of the top candidate
|
---|
98 | /// - PseudoJet non_W(): non-W subjet(s) of the top candidate (i.e. the b)
|
---|
99 | /// - double cos_theta_W(): the W helicity angle
|
---|
100 | /// - PseudoJet W1(): the harder of the two prongs of the W
|
---|
101 | /// - PseudoJet W2(): the softer of the two prongs of the W
|
---|
102 | ///
|
---|
103 | /// The structure of the top_candidate can also be accessed through its
|
---|
104 | /// pieces() function:
|
---|
105 | ///
|
---|
106 | /// - top_candidate.pieces()[0]: W
|
---|
107 | /// - top_candidate.pieces()[1]: non_W
|
---|
108 | ///
|
---|
109 | /// The W itself has two pieces (corresponding to W1, W2).
|
---|
110 | ///
|
---|
111 | /// The existence of the first two of the structural calls (W(),
|
---|
112 | /// non_W()) and the fact that the top is made of two pieces (W,
|
---|
113 | /// non_W) are features that should be common to all taggers derived
|
---|
114 | /// from TopTaggerBase.
|
---|
115 | ///
|
---|
116 | /// See also \subpage Example13 for a full usage example.
|
---|
117 | ///
|
---|
118 | class JHTopTagger : public TopTaggerBase {
|
---|
119 | public:
|
---|
120 | /// default ctor
|
---|
121 | /// The parameters are the following:
|
---|
122 | /// \param delta_p fractional pt cut imposed on the subjets
|
---|
123 | /// (computed as a fraction of the original jet)
|
---|
124 | /// \param delta_r minimal distance between 2 subjets
|
---|
125 | /// (computed as |y1-y2|+|phi1-phi2|)
|
---|
126 | /// \param cos_theta_W_max the maximal value for the polarisation
|
---|
127 | /// angle of the W
|
---|
128 | /// \param mW the W mass
|
---|
129 | ///
|
---|
130 | /// The default values of all these parameters are taken from
|
---|
131 | /// arXiv:0806:0848
|
---|
132 | JHTopTagger(const double delta_p=0.10, const double delta_r=0.19,
|
---|
133 | double cos_theta_W_max=0.7, double mW=80.4)
|
---|
134 | : _delta_p(delta_p), _delta_r(delta_r),
|
---|
135 | _cos_theta_W_max(cos_theta_W_max), _mW(mW){};
|
---|
136 |
|
---|
137 | /// returns a textual description of the tagger
|
---|
138 | virtual std::string description() const;
|
---|
139 |
|
---|
140 | /// runs the tagger on the given jet and
|
---|
141 | /// returns the tagged PseudoJet if successful, or a PseudoJet==0 otherwise
|
---|
142 | /// (standard access is through operator()).
|
---|
143 | /// \param jet the PseudoJet to tag
|
---|
144 | virtual PseudoJet result(const PseudoJet & jet) const;
|
---|
145 |
|
---|
146 | // the type of the associated structure
|
---|
147 | typedef JHTopTaggerStructure StructureType;
|
---|
148 |
|
---|
149 | protected:
|
---|
150 | /// runs the Johns Hopkins decomposition procedure
|
---|
151 | std::vector<PseudoJet> _split_once(const PseudoJet & jet_to_split,
|
---|
152 | const PseudoJet & reference_jet) const;
|
---|
153 |
|
---|
154 | double _delta_p, _delta_r, _cos_theta_W_max, _mW;
|
---|
155 | static LimitedWarning _warnings_nonca;
|
---|
156 | };
|
---|
157 |
|
---|
158 |
|
---|
159 | //------------------------------------------------------------------------
|
---|
160 | /// @ingroup tools_taggers
|
---|
161 | /// \class JHTopTaggerStructure
|
---|
162 | /// the structure returned by the JHTopTagger transformer.
|
---|
163 | ///
|
---|
164 | /// See the JHTopTagger class description for the details of what
|
---|
165 | /// is inside this structure
|
---|
166 | ///
|
---|
167 | class JHTopTaggerStructure : public CompositeJetStructure, public TopTaggerBaseStructure {
|
---|
168 | public:
|
---|
169 | /// ctor with pieces initialisation
|
---|
170 | JHTopTaggerStructure(std::vector<PseudoJet> pieces_in,
|
---|
171 | const JetDefinition::Recombiner *recombiner = 0) :
|
---|
172 | CompositeJetStructure(pieces_in, recombiner), _cos_theta_w(0.0){}
|
---|
173 |
|
---|
174 | /// returns the W subjet
|
---|
175 | inline const PseudoJet & W() const{
|
---|
176 | return _pieces[0];
|
---|
177 | }
|
---|
178 |
|
---|
179 | /// returns the first W subjet (the harder)
|
---|
180 | inline PseudoJet W1() const{
|
---|
181 | assert(W().pieces().size()>0);
|
---|
182 | return W().pieces()[0];
|
---|
183 | }
|
---|
184 |
|
---|
185 | /// returns the second W subjet
|
---|
186 | inline PseudoJet W2() const{
|
---|
187 | assert(W().pieces().size()>1);
|
---|
188 | return W().pieces()[1];
|
---|
189 | }
|
---|
190 |
|
---|
191 | /// returns the non-W subjet
|
---|
192 | /// It will have 1 or 2 pieces depending on whether the tagger has
|
---|
193 | /// found 3 or 4 pieces
|
---|
194 | inline const PseudoJet & non_W() const{
|
---|
195 | return _pieces[1];
|
---|
196 | }
|
---|
197 |
|
---|
198 | /// returns the W helicity angle
|
---|
199 | inline double cos_theta_W() const {return _cos_theta_w;}
|
---|
200 |
|
---|
201 | // /// returns the original jet (before tagging)
|
---|
202 | // const PseudoJet & original() const {return _original_jet;}
|
---|
203 |
|
---|
204 |
|
---|
205 | protected:
|
---|
206 | double _cos_theta_w; ///< the W helicity angle
|
---|
207 | //PseudoJet _W; ///< the tagged W
|
---|
208 | //PseudoJet _non_W; ///< the remaining pieces
|
---|
209 | // PseudoJet _original_jet; ///< the original jet (before tagging)
|
---|
210 |
|
---|
211 | // allow the tagger to set these
|
---|
212 | friend class JHTopTagger;
|
---|
213 | };
|
---|
214 |
|
---|
215 |
|
---|
216 |
|
---|
217 | FASTJET_END_NAMESPACE
|
---|
218 |
|
---|
219 | #endif // __FASTJET_JH_TOP_TAGGER_HH__
|
---|
220 |
|
---|