[35cdc46] | 1 | //FJSTARTHEADER
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[b7b836a] | 2 | // $Id: MassDropTagger.cc 4354 2018-04-22 07:12:37Z salam $
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[d7d2da3] | 3 | //
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[b7b836a] | 4 | // Copyright (c) 2005-2018, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
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[d7d2da3] | 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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[35cdc46] | 15 | // development. They are described in the original FastJet paper,
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| 16 | // hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use
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[d7d2da3] | 17 | // FastJet as part of work towards a scientific publication, please
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[35cdc46] | 18 | // quote the version you use and include a citation to the manual and
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| 19 | // optionally also to hep-ph/0512210.
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[d7d2da3] | 20 | //
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| 21 | // FastJet is distributed in the hope that it will be useful,
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| 22 | // but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 23 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 24 | // GNU General Public License for more details.
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| 25 | //
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| 26 | // You should have received a copy of the GNU General Public License
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| 27 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>.
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| 28 | //----------------------------------------------------------------------
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[35cdc46] | 29 | //FJENDHEADER
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[d7d2da3] | 30 |
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| 31 | #include <fastjet/tools/MassDropTagger.hh>
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| 32 | #include <fastjet/ClusterSequence.hh>
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| 33 | #include <sstream>
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| 34 |
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| 35 | FASTJET_BEGIN_NAMESPACE
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| 36 |
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| 37 | LimitedWarning MassDropTagger::_warnings_nonca;
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[b7b836a] | 38 | LimitedWarning MassDropTagger::_negative_mass_warning;
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[d7d2da3] | 39 |
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| 40 | using namespace std;
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| 41 |
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| 42 | //----------------------------------------------------------------------
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| 43 | // MassDropTagger class implementation
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| 44 | //----------------------------------------------------------------------
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| 45 |
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| 46 | //------------------------------------------------------------------------
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| 47 | // description of the tagger
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| 48 | string MassDropTagger::description() const{
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| 49 | ostringstream oss;
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| 50 | oss << "MassDropTagger with mu=" << _mu << " and ycut=" << _ycut;
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| 51 | return oss.str();
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| 52 | }
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| 53 |
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| 54 | //------------------------------------------------------------------------
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| 55 | // returns the tagged PseudoJet if successful, 0 otherwise
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| 56 | // - jet the PseudoJet to tag
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| 57 | PseudoJet MassDropTagger::result(const PseudoJet & jet) const{
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| 58 | PseudoJet j = jet;
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| 59 |
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| 60 | // issue a warning if the jet is not obtained through a C/A
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| 61 | // clustering
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| 62 | if ((! j.has_associated_cluster_sequence()) ||
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[d69dfe4] | 63 | (j.validated_cs()->jet_def().jet_algorithm() != cambridge_algorithm))
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[d7d2da3] | 64 | _warnings_nonca.warn("MassDropTagger should only be applied on jets from a Cambridge/Aachen clustering; use it with other algorithms at your own risk.");
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| 65 |
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| 66 |
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| 67 | PseudoJet j1, j2;
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| 68 | bool had_parents;
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| 69 |
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| 70 | // we just ask that we can "walk" in the cluster sequence.
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| 71 | // appropriate errors will be thrown automatically if this is not
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| 72 | // the case
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| 73 | while ((had_parents = j.has_parents(j1,j2))) {
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[b7b836a] | 74 | if (j.m2() <= 0) {
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| 75 | _negative_mass_warning.warn(
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| 76 | "MassDropTagger: parent (sub)jet has mass^2<=0; returning null jet");
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| 77 | return PseudoJet();
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| 78 | }
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[d7d2da3] | 79 | // make parent1 the more massive jet
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| 80 | if (j1.m2() < j2.m2()) std::swap(j1,j2);
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| 81 |
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| 82 | // if we pass the conditions on the mass drop and its degree of
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| 83 | // asymmetry (kt_dist/m^2 > rtycut [where kt_dist/m^2 \sim
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| 84 | // z/(1-z)), then we've found something interesting, so exit the
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| 85 | // loop
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| 86 | if ( (j1.m2() < _mu*_mu*j.m2()) && (j1.kt_distance(j2) > _ycut*j.m2()) )
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| 87 | break;
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| 88 | else
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| 89 | j = j1;
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| 90 | }
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| 91 |
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| 92 | if (!had_parents)
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| 93 | // no Higgs found, return an empty PseudoJet
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| 94 | return PseudoJet();
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| 95 |
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| 96 | // create the result and its structure
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| 97 | PseudoJet result_local = j;
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| 98 | MassDropTaggerStructure * s = new MassDropTaggerStructure(result_local);
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[b7b836a] | 99 | s->_mu = j1.m() / j.m();
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| 100 | s->_y = j1.kt_distance(j2)/j.m2();
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[d7d2da3] | 101 |
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| 102 | result_local.set_structure_shared_ptr(SharedPtr<PseudoJetStructureBase>(s));
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| 103 |
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| 104 | return result_local;
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| 105 | }
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| 106 |
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| 107 | FASTJET_END_NAMESPACE
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| 108 |
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