FastJet 3.0.2
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00001 //STARTHEADER 00002 // $Id: Subtractor.cc 2577 2011-09-13 15:11:38Z salam $ 00003 // 00004 // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez 00005 // 00006 //---------------------------------------------------------------------- 00007 // This file is part of FastJet. 00008 // 00009 // FastJet is free software; you can redistribute it and/or modify 00010 // it under the terms of the GNU General Public License as published by 00011 // the Free Software Foundation; either version 2 of the License, or 00012 // (at your option) any later version. 00013 // 00014 // The algorithms that underlie FastJet have required considerable 00015 // development and are described in hep-ph/0512210. If you use 00016 // FastJet as part of work towards a scientific publication, please 00017 // include a citation to the FastJet paper. 00018 // 00019 // FastJet is distributed in the hope that it will be useful, 00020 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00021 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00022 // GNU General Public License for more details. 00023 // 00024 // You should have received a copy of the GNU General Public License 00025 // along with FastJet. If not, see <http://www.gnu.org/licenses/>. 00026 //---------------------------------------------------------------------- 00027 //ENDHEADER 00028 00029 #include "fastjet/tools/Subtractor.hh" 00030 #include <cassert> 00031 #include <sstream> 00032 #include <limits> 00033 using namespace std; 00034 00035 FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh 00036 00037 const double Subtractor::_invalid_rho = -numeric_limits<double>::infinity(); 00038 00039 00040 Subtractor::Subtractor(double rho) : _bge(0), _rho(rho) { 00041 assert(_rho>0.0); 00042 } 00043 00044 PseudoJet Subtractor::result(const PseudoJet & jet) const { 00045 if (!jet.has_area()){ 00046 throw Error("Trying to subtract a jet without area support"); 00047 } 00048 00049 double rho; 00050 if (_bge != 0) { 00051 rho = _bge->rho(jet); 00052 } else if (_rho != _invalid_rho) { 00053 rho = _rho; 00054 } else { 00055 throw Error("default Subtractor does not have any information about the background, which is needed to perform the subtraction"); 00056 } 00057 00058 PseudoJet subtracted_jet = jet; 00059 PseudoJet area4vect = jet.area_4vector(); 00060 // sanity check 00061 if (rho*area4vect.perp() < jet.perp() ) { 00062 // this subtraction should retain the jet's structural 00063 // information 00064 subtracted_jet -= rho*area4vect; 00065 } else { 00066 // this sets the jet's momentum to zero while 00067 // maintaining all of the jet's structural information 00068 subtracted_jet *= 0; 00069 } 00070 return subtracted_jet; 00071 } 00072 00073 //---------------------------------------------------------------------- 00074 std::string Subtractor::description() const{ 00075 if (_bge != 0) { 00076 return "Subtractor that uses the following background estimator to determine rho: "+_bge->description(); 00077 } else if (_rho != _invalid_rho) { 00078 ostringstream ostr; 00079 ostr << "Subtractor that uses a fixed value of rho = " << _rho; 00080 return ostr.str(); 00081 } else { 00082 return "Uninitialised subtractor"; 00083 } 00084 } 00085 00086 FASTJET_END_NAMESPACE