1 | //STARTHEADER |
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2 | // $Id: Subtractor.cc 999 2013-03-04 11:48:06Z pavel $ |
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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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