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source: svn/trunk/external/fastjet/tools/BackgroundEstimatorBase.hh@ 1204

Last change on this file since 1204 was 999, checked in by Pavel Demin, 12 years ago

add fastjet/tools

File size: 7.7 KB
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1#ifndef __FASTJET_BACKGROUND_ESTIMATOR_BASE_HH__
2#define __FASTJET_BACKGROUND_ESTIMATOR_BASE_HH__
3
4//STARTHEADER
5// $Id: BackgroundEstimatorBase.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/ClusterSequenceAreaBase.hh>
33#include <fastjet/FunctionOfPseudoJet.hh>
34#include <fastjet/Selector.hh>
35#include <fastjet/Error.hh>
36#include <iostream>
37
38FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
39
40
41/// @ingroup tools_background
42/// \class BackgroundEstimatorBase
43///
44/// Abstract base class that provides the basic interface for classes
45/// that estimate levels of background radiation in hadrion and
46/// heavy-ion collider events.
47///
48///
49class BackgroundEstimatorBase {
50public:
51 /// @name constructors and destructors
52 //\{
53 //----------------------------------------------------------------
54 BackgroundEstimatorBase() : _rescaling_class(0) {}
55 //\}
56
57 /// a default virtual destructor that does nothing
58 virtual ~BackgroundEstimatorBase() {}
59
60
61 /// @name setting a new event
62 //\{
63 //----------------------------------------------------------------
64
65 /// tell the background estimator that it has a new event, composed
66 /// of the specified particles.
67 virtual void set_particles(const std::vector<PseudoJet> & particles) = 0;
68
69 //\}
70
71 /// @name retrieving fundamental information
72 //\{
73 //----------------------------------------------------------------
74
75 /// get rho, the background density per unit area
76 virtual double rho() const = 0;
77
78 /// get sigma, the background fluctuations per unit area; must be
79 /// multipled by sqrt(area) to get fluctuations for a region of a
80 /// given area.
81 virtual double sigma() const {
82 throw Error("sigma() not supported for this Background Estimator");
83 }
84
85 /// get rho, the background density per unit area, locally at the
86 /// position of a given jet. Note that this is not const, because a
87 /// user may then wish to query other aspects of the background that
88 /// could depend on the position of the jet last used for a rho(jet)
89 /// determination.
90 virtual double rho(const PseudoJet & jet) = 0;
91
92 /// get sigma, the background fluctuations per unit area, locally at
93 /// the position of a given jet. As for rho(jet), it is non-const.
94 virtual double sigma(const PseudoJet & /*jet*/) {
95 throw Error("sigma(jet) not supported for this Background Estimator");
96 }
97
98 /// returns true if this background estimator has support for
99 /// determination of sigma
100 virtual bool has_sigma() {return false;}
101 //\}
102
103
104 /// @name configuring the behaviour
105 //\{
106 //----------------------------------------------------------------
107
108 /// Set a pointer to a class that calculates the rescaling factor as
109 /// a function of the jet (position). Note that the rescaling factor
110 /// is used both in the determination of the "global" rho (the pt/A
111 /// of each jet is divided by this factor) and when asking for a
112 /// local rho (the result is multiplied by this factor).
113 ///
114 /// The BackgroundRescalingYPolynomial class can be used to get a
115 /// rescaling that depends just on rapidity.
116 virtual void set_rescaling_class(const FunctionOfPseudoJet<double> * rescaling_class_in) { _rescaling_class = rescaling_class_in; }
117
118 /// return the pointer to the jet density class
119 const FunctionOfPseudoJet<double> * rescaling_class() const{
120 return _rescaling_class;
121 }
122
123 //\}
124
125 /// @name description
126 //\{
127 //----------------------------------------------------------------
128
129 /// returns a textual description of the background estimator
130 virtual std::string description() const = 0;
131
132 //\}
133
134protected:
135 /// @name helpers for derived classes
136 ///
137 /// Note that these helpers are related to median-based estimation
138 /// of the background, so there is no guarantee that they will
139 /// remain in this base class in the long term
140 //\{
141 //----------------------------------------------------------------
142
143 /// given a quantity in a vector (e.g. pt_over_area) and knowledge
144 /// about the number of empty jets, calculate the median and
145 /// stand_dev_if_gaussian (roughly from the 16th percentile)
146 ///
147 /// If do_fj2_calculation is set to true then this performs FastJet
148 /// 2.X estimation of the standard deviation, which has a spurious
149 /// offset in the limit of a small number of jets.
150 void _median_and_stddev(const std::vector<double> & quantity_vector,
151 double n_empty_jets,
152 double & median,
153 double & stand_dev_if_gaussian,
154 bool do_fj2_calculation = false
155 ) const;
156
157 /// computes a percentile of a given _sorted_ vector
158 /// \param sorted_quantity_vector the vector contains the data sample
159 /// \param percentile the percentile (defined between 0 and 1) to compute
160 /// \param nempty an additional number of 0's
161 /// (considered at the beginning of
162 /// the quantity vector)
163 /// \param do_fj2_calculation carry out the calculation as it
164 /// was done in fj2 (suffers from "edge effects")
165 double _percentile(const std::vector<double> & sorted_quantity_vector,
166 const double percentile,
167 const double nempty=0.0,
168 const bool do_fj2_calculation = false) const;
169
170 //\}
171
172 const FunctionOfPseudoJet<double> * _rescaling_class;
173 static LimitedWarning _warnings_empty_area;
174};
175
176
177
178//----------------------------------------------------------------------
179/// @ingroup tools_background
180/// A background rescaling that is a simple polynomial in y
181class BackgroundRescalingYPolynomial : public FunctionOfPseudoJet<double> {
182public:
183 /// construct a background rescaling polynomial of the form
184 /// a0 + a1*y + a2*y^2 + a3*y^3 + a4*y^4
185 ///
186 /// The following values give a reasonable reproduction of the
187 /// Pythia8 tune 4C background shape for pp collisions at
188 /// sqrt(s)=7TeV:
189 ///
190 /// - a0 = 1.157
191 /// - a1 = 0
192 /// - a2 = -0.0266
193 /// - a3 = 0
194 /// - a4 = 0.000048
195 ///
196 BackgroundRescalingYPolynomial(double a0=1,
197 double a1=0,
198 double a2=0,
199 double a3=0,
200 double a4=0) : _a0(a0), _a1(a1), _a2(a2), _a3(a3), _a4(a4) {}
201
202 /// return the rescaling factor associated with this jet
203 virtual double result(const PseudoJet & jet) const;
204private:
205 double _a0, _a1, _a2, _a3, _a4;
206};
207
208
209
210
211
212FASTJET_END_NAMESPACE
213
214#endif // __BACKGROUND_ESTIMATOR_BASE_HH__
215
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