| 1 | //STARTHEADER
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| 2 | // $Id$
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| 3 | //
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| 4 | // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
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| 5 | //
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| 6 | //----------------------------------------------------------------------
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| 7 | // This file is part of FastJet.
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| 8 | //
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| 9 | // FastJet is free software; you can redistribute it and/or modify
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| 10 | // it under the terms of the GNU General Public License as published by
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| 11 | // the Free Software Foundation; either version 2 of the License, or
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| 12 | // (at your option) any later version.
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| 13 | //
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| 14 | // The algorithms that underlie FastJet have required considerable
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| 15 | // development and are described in hep-ph/0512210. If you use
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| 16 | // FastJet as part of work towards a scientific publication, please
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| 17 | // include a citation to the FastJet paper.
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| 18 | //
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| 19 | // FastJet is distributed in the hope that it will be useful,
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| 20 | // but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 21 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 22 | // GNU General Public License for more details.
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| 23 | //
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| 24 | // You should have received a copy of the GNU General Public License
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| 25 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>.
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| 26 | //----------------------------------------------------------------------
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| 27 | //ENDHEADER
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| 28 |
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| 29 | #include "fastjet/tools/Subtractor.hh"
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| 30 | #include <cassert>
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| 31 | #include <sstream>
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| 32 | #include <limits>
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| 33 | using namespace std;
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| 34 |
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| 35 | FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
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| 36 |
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| 37 | const double Subtractor::_invalid_rho = -numeric_limits<double>::infinity();
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| 38 |
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| 39 |
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| 40 | Subtractor::Subtractor(double rho) : _bge(0), _rho(rho) {
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| 41 | assert(_rho>0.0);
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| 42 | }
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| 43 |
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| 44 | PseudoJet Subtractor::result(const PseudoJet & jet) const {
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| 45 | if (!jet.has_area()){
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| 46 | throw Error("Trying to subtract a jet without area support");
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| 47 | }
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| 48 |
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| 49 | double rho;
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| 50 | if (_bge != 0) {
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| 51 | rho = _bge->rho(jet);
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| 52 | } else if (_rho != _invalid_rho) {
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| 53 | rho = _rho;
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| 54 | } else {
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| 55 | throw Error("default Subtractor does not have any information about the background, which is needed to perform the subtraction");
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| 56 | }
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| 57 |
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| 58 | PseudoJet subtracted_jet = jet;
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| 59 | PseudoJet area4vect = jet.area_4vector();
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| 60 | // sanity check
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| 61 | if (rho*area4vect.perp() < jet.perp() ) {
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| 62 | // this subtraction should retain the jet's structural
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| 63 | // information
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| 64 | subtracted_jet -= rho*area4vect;
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| 65 | } else {
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| 66 | // this sets the jet's momentum to zero while
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| 67 | // maintaining all of the jet's structural information
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| 68 | subtracted_jet *= 0;
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| 69 | }
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| 70 | return subtracted_jet;
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| 71 | }
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| 72 |
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| 73 | //----------------------------------------------------------------------
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| 74 | std::string Subtractor::description() const{
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| 75 | if (_bge != 0) {
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| 76 | return "Subtractor that uses the following background estimator to determine rho: "+_bge->description();
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| 77 | } else if (_rho != _invalid_rho) {
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| 78 | ostringstream ostr;
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| 79 | ostr << "Subtractor that uses a fixed value of rho = " << _rho;
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| 80 | return ostr.str();
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| 81 | } else {
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| 82 | return "Uninitialised subtractor";
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| 83 | }
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| 84 | }
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| 85 |
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| 86 | FASTJET_END_NAMESPACE
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