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source: svn/trunk/external/fastjet/tools/Subtractor.cc@ 1204

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

add fastjet/tools

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id Revision Date
File size: 2.8 KB
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1//STARTHEADER
2// $Id: Subtractor.cc 999 2013-03-04 11:48:06Z pavel $
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#include "fastjet/tools/Subtractor.hh"
30#include <cassert>
31#include <sstream>
32#include <limits>
33using namespace std;
34
35FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
36
37const double Subtractor::_invalid_rho = -numeric_limits<double>::infinity();
38
39
40Subtractor::Subtractor(double rho) : _bge(0), _rho(rho) {
41 assert(_rho>0.0);
42}
43
44PseudoJet Subtractor::result(const PseudoJet & jet) const {
45 if (!jet.has_area()){
46 throw Error("Trying to subtract a jet without area support");
47 }
48
49 double rho;
50 if (_bge != 0) {
51 rho = _bge->rho(jet);
52 } else if (_rho != _invalid_rho) {
53 rho = _rho;
54 } else {
55 throw Error("default Subtractor does not have any information about the background, which is needed to perform the subtraction");
56 }
57
58 PseudoJet subtracted_jet = jet;
59 PseudoJet area4vect = jet.area_4vector();
60 // sanity check
61 if (rho*area4vect.perp() < jet.perp() ) {
62 // this subtraction should retain the jet's structural
63 // information
64 subtracted_jet -= rho*area4vect;
65 } else {
66 // this sets the jet's momentum to zero while
67 // maintaining all of the jet's structural information
68 subtracted_jet *= 0;
69 }
70 return subtracted_jet;
71}
72
73//----------------------------------------------------------------------
74std::string Subtractor::description() const{
75 if (_bge != 0) {
76 return "Subtractor that uses the following background estimator to determine rho: "+_bge->description();
77 } else if (_rho != _invalid_rho) {
78 ostringstream ostr;
79 ostr << "Subtractor that uses a fixed value of rho = " << _rho;
80 return ostr.str();
81 } else {
82 return "Uninitialised subtractor";
83 }
84}
85
86FASTJET_END_NAMESPACE
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