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1//STARTHEADER
2// $Id: ClusterSequenceAreaBase.hh 2687 2011-11-14 11:17:51Z soyez $
3//
4// Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
5//
6//----------------------------------------------------------------------
7// This file is part of FastJet.
8//
9// FastJet is free software; you can redistribute it and/or modify
10// it under the terms of the GNU General Public License as published by
11// the Free Software Foundation; either version 2 of the License, or
12// (at your option) any later version.
13//
14// The algorithms that underlie FastJet have required considerable
15// development and are described in hep-ph/0512210. If you use
16// FastJet as part of work towards a scientific publication, please
17// include a citation to the FastJet paper.
18//
19// FastJet is distributed in the hope that it will be useful,
20// but WITHOUT ANY WARRANTY; without even the implied warranty of
21// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22// GNU General Public License for more details.
23//
24// You should have received a copy of the GNU General Public License
25// along with FastJet. If not, see <http://www.gnu.org/licenses/>.
26//----------------------------------------------------------------------
27//ENDHEADER
28
29#ifndef __FASTJET_CLUSTERSEQUENCEAREABASE_HH__
30#define __FASTJET_CLUSTERSEQUENCEAREABASE_HH__
31
32#include "fastjet/ClusterSequence.hh"
33#include "fastjet/LimitedWarning.hh"
34#include "fastjet/Selector.hh"
35
36FASTJET_BEGIN_NAMESPACE
37
38/// @ingroup area_classes
39/// \class ClusterSequenceAreaBase
40/// base class that sets interface for extensions of ClusterSequence
41/// that provide information about the area of each jet
42///
43/// the virtual functions here all return 0, since no area determination
44/// is implemented.
45class ClusterSequenceAreaBase : public ClusterSequence {
46public:
47
48 /// a constructor which just carries out the construction of the
49 /// parent class
50 template<class L> ClusterSequenceAreaBase
51 (const std::vector<L> & pseudojets,
52 const JetDefinition & jet_def_in,
53 const bool & writeout_combinations = false) :
54 ClusterSequence(pseudojets, jet_def_in, writeout_combinations) {}
55
56
57 /// default constructor
58 ClusterSequenceAreaBase() {}
59
60
61 /// destructor
62 virtual ~ClusterSequenceAreaBase() {}
63
64
65 /// return the area associated with the given jet; this base class
66 /// returns 0.
67 virtual double area (const PseudoJet & ) const {return 0.0;}
68
69 /// return the error (uncertainty) associated with the determination
70 /// of the area of this jet; this base class returns 0.
71 virtual double area_error (const PseudoJet & ) const {return 0.0;}
72
73 /// return a PseudoJet whose 4-vector is defined by the following integral
74 ///
75 /// \int drap d\phi PseudoJet("rap,phi,pt=one") *
76 /// * Theta("rap,phi inside jet boundary")
77 ///
78 /// where PseudoJet("rap,phi,pt=one") is a 4-vector with the given
79 /// rapidity (rap), azimuth (phi) and pt=1, while Theta("rap,phi
80 /// inside jet boundary") is a function that is 1 when rap,phi
81 /// define a direction inside the jet boundary and 0 otherwise.
82 ///
83 /// This base class returns a null 4-vector.
84 virtual PseudoJet area_4vector(const PseudoJet & ) const {
85 return PseudoJet(0.0,0.0,0.0,0.0);}
86
87 /// true if a jet is made exclusively of ghosts
88 ///
89 /// NB: most area classes do not give any explicit ghost jets, but
90 /// some do, and they should replace this function with their own
91 /// version.
92 virtual bool is_pure_ghost(const PseudoJet & ) const {
93 return false;
94 }
95
96 /// returns true if ghosts are explicitly included within
97 /// jets for this ClusterSequence;
98 ///
99 /// Derived classes that do include explicit ghosts should provide
100 /// an alternative version of this routine and set it properly.
101 virtual bool has_explicit_ghosts() const {
102 return false;
103 }
104
105 /// return the total area, corresponding to the given Selector, that
106 /// is free of jets, in general based on the inclusive jets.
107 ///
108 /// The selector passed as an argument has to have a finite area and
109 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
110 /// tools for more generic usages)
111 virtual double empty_area(const Selector & selector) const;
112
113 /// return the total area, corresponding to the given Selector, that
114 /// is free of jets, based on the supplied all_jets
115 ///
116 /// The selector passed as an argument has to have a finite area and
117 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
118 /// tools for more generic usages)
119 double empty_area_from_jets(const std::vector<PseudoJet> & all_jets,
120 const Selector & selector) const;
121
122 /// return something similar to the number of pure ghost jets
123 /// in the given selector's range in an active area case.
124 /// For the local implementation we return empty_area/(0.55 pi R^2),
125 /// based on measured properties of ghost jets with kt and cam
126 /// (cf arXiv:0802.1188).
127 ///
128 /// Note that the number returned is a double.
129 ///
130 /// The selector passed as an argument has to have a finite area and
131 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
132 /// tools for more generic usages)
133 virtual double n_empty_jets(const Selector & selector) const {
134 double R = jet_def().R();
135 return empty_area(selector)/(0.55*pi*R*R);
136 }
137
138 /// the median of (pt/area) for jets contained within the selector
139 /// range, making use also of the info on n_empty_jets
140 ///
141 /// The selector passed as an argument has to have a finite area and
142 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
143 /// tools for more generic usages)
144 double median_pt_per_unit_area(const Selector & selector) const;
145
146 /// the median of (pt/area_4vector) for jets contained within the
147 /// selector range, making use also of the info on n_empty_jets
148 ///
149 /// The selector passed as an argument has to have a finite area and
150 /// apply jet-by-jet
151 double median_pt_per_unit_area_4vector(const Selector & selector) const;
152
153 /// the function that does the work for median_pt_per_unit_area and
154 /// median_pt_per_unit_area_4vector:
155 /// - something_is_area_4vect = false -> use plain area
156 /// - something_is_area_4vect = true -> use 4-vector area
157 double median_pt_per_unit_something(
158 const Selector & selector, bool use_area_4vector) const;
159
160 /// using jets withing the selector range (and with 4-vector areas if
161 /// use_area_4vector), calculate the median pt/area, as well as an
162 /// "error" (uncertainty), which is defined as the 1-sigma
163 /// half-width of the distribution of pt/A, obtained by looking for
164 /// the point below which we have (1-0.6827)/2 of the jets
165 /// (including empty jets).
166 ///
167 /// The subtraction for a jet with uncorrected pt pt^U and area A is
168 ///
169 /// pt^S = pt^U - median*A +- sigma*sqrt(A)
170 ///
171 /// where the error is only that associated with the fluctuations
172 /// in the noise and not that associated with the noise having
173 /// caused changes in the hard-particle content of the jet.
174 ///
175 /// The selector passed as an argument has to have a finite area and
176 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
177 /// tools for more generic usages)
178 ///
179 /// NB: subtraction may also be done with 4-vector area of course,
180 /// and this is recommended for jets with larger values of R, as
181 /// long as rho has also been determined with a 4-vector area;
182 /// using a scalar area causes one to neglect terms of relative
183 /// order $R^2/8$ in the jet $p_t$.
184 virtual void get_median_rho_and_sigma(const Selector & selector,
185 bool use_area_4vector,
186 double & median, double & sigma,
187 double & mean_area) const;
188
189 /// a more advanced version of get_median_rho_and_sigma, which allows
190 /// one to use any "view" of the event containing all jets (so that,
191 /// e.g. one might use Cam on a different resolution scale without
192 /// have to rerun the algorithm).
193 ///
194 /// By default it will assume that "all" are not inclusive jets,
195 /// so that in dealing with empty area it has to calculate
196 /// the number of empty jets based on the empty area and the
197 /// the observed <area> of jets rather than a surmised area
198 ///
199 /// Note that for small effective radii, this can cause problems
200 /// because the harder jets get an area >> <ghost-jet-area>
201 /// and so the estimate comes out all wrong. In these situations
202 /// it is highly advisable to use an area with explicit ghosts, since
203 /// then the "empty" jets are actually visible.
204 ///
205 /// The selector passed as an argument has to have a finite area and
206 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
207 /// tools for more generic usages)
208 virtual void get_median_rho_and_sigma(const std::vector<PseudoJet> & all_jets,
209 const Selector & selector,
210 bool use_area_4vector,
211 double & median, double & sigma,
212 double & mean_area,
213 bool all_are_inclusive = false) const;
214
215 /// same as the full version of get_median_rho_and_error, but without
216 /// access to the mean_area
217 ///
218 /// The selector passed as an argument has to have a finite area and
219 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
220 /// tools for more generic usages)
221 virtual void get_median_rho_and_sigma(const Selector & selector,
222 bool use_area_4vector,
223 double & median, double & sigma) const {
224 double mean_area;
225 get_median_rho_and_sigma(selector, use_area_4vector,
226 median, sigma, mean_area);
227 }
228
229
230 /// fits a form pt_per_unit_area(y) = a + b*y^2 in the selector range.
231 /// exclude_above allows one to exclude large values of pt/area from fit.
232 /// (if negative, the cut is discarded)
233 /// use_area_4vector = true uses the 4vector areas.
234 ///
235 /// The selector passed as an argument has to have a finite area and
236 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
237 /// tools for more generic usages)
238 virtual void parabolic_pt_per_unit_area(double & a, double & b,
239 const Selector & selector,
240 double exclude_above=-1.0,
241 bool use_area_4vector=false) const;
242
243 /// return a vector of all subtracted jets, using area_4vector, given rho.
244 /// Only inclusive_jets above ptmin are subtracted and returned.
245 /// the ordering is the same as that of sorted_by_pt(cs.inclusive_jets()),
246 /// i.e. not necessarily ordered in pt once subtracted
247 std::vector<PseudoJet> subtracted_jets(const double rho,
248 const double ptmin=0.0) const;
249
250 /// return a vector of subtracted jets, using area_4vector.
251 /// Only inclusive_jets above ptmin are subtracted and returned.
252 /// the ordering is the same as that of sorted_by_pt(cs.inclusive_jets()),
253 /// i.e. not necessarily ordered in pt once subtracted
254 ///
255 /// The selector passed as an argument has to have a finite area and
256 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
257 /// tools for more generic usages)
258 std::vector<PseudoJet> subtracted_jets(const Selector & selector,
259 const double ptmin=0.0) const;
260
261 /// return a subtracted jet, using area_4vector, given rho
262 PseudoJet subtracted_jet(const PseudoJet & jet,
263 const double rho) const;
264
265 /// return a subtracted jet, using area_4vector; note
266 /// that this is potentially inefficient if repeatedly used for many
267 /// different jets, because rho will be recalculated each time
268 /// around.
269 ///
270 /// The selector passed as an argument has to have a finite area and
271 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
272 /// tools for more generic usages)
273 PseudoJet subtracted_jet(const PseudoJet & jet,
274 const Selector & selector) const;
275
276 /// return the subtracted pt, given rho
277 double subtracted_pt(const PseudoJet & jet,
278 const double rho,
279 bool use_area_4vector=false) const;
280
281 /// return the subtracted pt; note that this is
282 /// potentially inefficient if repeatedly used for many different
283 /// jets, because rho will be recalculated each time around.
284 ///
285 /// The selector passed as an argument has to have a finite area and
286 /// apply jet-by-jet (see the BackgroundEstimator and Subtractor
287 /// tools for more generic usages)
288 double subtracted_pt(const PseudoJet & jet,
289 const Selector & selector,
290 bool use_area_4vector=false) const;
291
292protected:
293 /// check the selector is suited for the computations i.e. applies jet by jet and has a finite area
294 void _check_selector_good_for_median(const Selector &selector) const;
295
296
297private:
298 /// handle warning messages
299 static LimitedWarning _warnings;
300 static LimitedWarning _warnings_zero_area;
301 static LimitedWarning _warnings_empty_area;
302
303 /// check the jet algorithm is suitable (and if not issue a warning)
304 void _check_jet_alg_good_for_median() const;
305
306};
307
308
309
310FASTJET_END_NAMESPACE
311
312#endif // __FASTJET_CLUSTERSEQUENCEAREABASE_HH__
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