1 //FJSTARTHEADER 2 // $Id: CDFMidPointPlugin.hh 4442 2020-05-05 07:50:11Z soyez $ 3 // 4 // Copyright (c) 2005-2020, 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. They are described in the original FastJet paper, 16 // hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use 17 // FastJet as part of work towards a scientific publication, please 18 // quote the version you use and include a citation to the manual and 19 // optionally also to hep-ph/0512210. 20 // 21 // FastJet is distributed in the hope that it will be useful, 22 // but WITHOUT ANY WARRANTY; without even the implied warranty of 23 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 24 // GNU General Public License for more details. 25 // 26 // You should have received a copy of the GNU General Public License 27 // along with FastJet. If not, see <http://www.gnu.org/licenses/>. 28 //---------------------------------------------------------------------- 29 //FJENDHEADER 30 31 #ifndef __CDFMIDPOINTPLUGIN_HH__ 32 #define __CDFMIDPOINTPLUGIN_HH__ 33 34 #include "fastjet/JetDefinition.hh" 35 36 // questionable whether this should be in fastjet namespace or not... 37 38 FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh 39 40 //---------------------------------------------------------------------- 41 // 42 /// @ingroup plugins 43 /// \class CDFMidPointPlugin 44 /// Implementation of the MidPoint algorithm from CDF (plugin for 45 /// fastjet-v2.1 upwards) 46 /// 47 /// A plugin for fastjet-v2.1 that provides an interface to the CDF 48 /// midpoint algorithm 49 /// 50 /// CDFMidPointPlugin is a plugin for fastjet (v2.1 upwards) that 51 /// provides an interface to the CDF version of Run-II iterative cone 52 /// algorithm with midpoint seeds (also known as the Iterative Legacy 53 /// Cone Algorithm, ILCA). 54 /// 55 /// The CDF code has been taken from Joey Huston's webpage 56 /// http://www.pa.msu.edu/~huston/Les_Houches_2005/Les_Houches_SM.html 57 /// 58 /// Note that the CDF midpoint code contains options that go beyond 59 /// those described in the Tevatron run-II document (hep-ex/0005012), 60 /// notably search-cones, as described in hep-ph/0111434, and 61 /// midpoints bewteen multiplets of stable cones. 62 /// 63 /// Additionally, the version of the CDF midpoint code distributed 64 /// here has been modified by the FastJet authors, so as to allow one 65 /// to choose the scale used in the split-merge step. 66 // 67 //---------------------------------------------------------------------- 68 class CDFMidPointPlugin : public JetDefinition::Plugin { 69 public: 70 /// the choice of scale to be used in the split-merge step 71 // NB: just replicates what we've added to the CDF midpoint code 72 enum SplitMergeScale {SM_pt, SM_Et, SM_mt, SM_pttilde}; 73 74 /// 75 /// A CDFMidPointPlugin constructor that looks like the one provided 76 /// by CDF. Its arguments should have the following meaning: 77 /// 78 /// - seed_threshold: minimum pt for a particle to be considered 79 /// a seed of the iteration. 80 /// 81 /// - cone_radius: standard meaning 82 /// 83 /// - cone_area_fraction: stable-cones are searched for with a 84 /// radius Rsearch = R * sqrt(cone_area_fraction), and then 85 /// expanded to size R afterwards; note (hep-ph/0610012) that this 86 /// introduces IR unsafety at NLO for X+2-jet observables (where X 87 /// any hard object). 88 /// 89 /// - max_pair_size: "midpoints" can be added between pairs of 90 /// stable cones, triplets of stable cones, etc.; max_pair_size 91 /// indicates the maximum number of stable cones that are 92 /// assembled when adding midpoints. 93 /// 94 /// - max_iterations: the maximum number of iterations to carry out 95 /// when looking for a stable cone. 96 /// 97 /// - overlap_threshold: if 98 /// (overlapping_Et)/(Et_of_softer_protojet) < overlap_threshold, 99 /// overlapping jets are split, otherwise they are merged. 100 /// 101 /// - sm_scale: a choice for the scale to be used in the split-merge 102 /// step (both for ordering the momenta and quantifying the 103 /// overlap); the three options are 104 /// 105 /// . SM_pt: pt (default -- source of small IR safety issue in purely 106 /// hadronic events) 107 /// 108 /// . SM_Et: Et (not boost invariant, reduces to mt at zero rapidity and 109 /// to pt and infinite rapidity) 110 /// 111 /// . SM_mt: transverse mass = sqrt(m^2+pt^2) 112 /// CDFMidPointPlugin(double seed_threshold_in,double cone_radius_in,double cone_area_fraction_in,int max_pair_size_in,int max_iterations_in,double overlap_threshold_in,SplitMergeScale sm_scale_in=SM_pt)113 CDFMidPointPlugin ( 114 double seed_threshold_in , 115 double cone_radius_in , 116 double cone_area_fraction_in , 117 int max_pair_size_in , 118 int max_iterations_in , 119 double overlap_threshold_in , 120 SplitMergeScale sm_scale_in = SM_pt) : 121 _seed_threshold (seed_threshold_in ), 122 _cone_radius (cone_radius_in ), 123 _cone_area_fraction (cone_area_fraction_in ), 124 _max_pair_size (max_pair_size_in ), 125 _max_iterations (max_iterations_in ), 126 _overlap_threshold (overlap_threshold_in ), 127 _sm_scale (sm_scale_in) {} 128 129 /// a compact constructor 130 /// 131 /// NB: as of version 2.4, the default value for the 132 /// overlap_threshold threshold has been removed, to avoid 133 /// misleading people into using the value of 0.5 without thinking, 134 /// which is known to have adverse effects in high-noise 135 /// environments. A recommended value is 0.75. CDFMidPointPlugin(double cone_radius_in,double overlap_threshold_in,double seed_threshold_in=1.0,double cone_area_fraction_in=1.0)136 CDFMidPointPlugin (double cone_radius_in, 137 double overlap_threshold_in,// = 0.5, 138 double seed_threshold_in = 1.0, 139 double cone_area_fraction_in = 1.0) : 140 _seed_threshold (seed_threshold_in ), 141 _cone_radius (cone_radius_in ), 142 _cone_area_fraction (cone_area_fraction_in ), 143 _max_pair_size (2 ), 144 _max_iterations (100 ), 145 _overlap_threshold (overlap_threshold_in ), 146 _sm_scale (SM_pt) {} 147 148 149 // some functions to return info about parameters seed_threshold() const150 double seed_threshold () const {return _seed_threshold ;} cone_radius() const151 double cone_radius () const {return _cone_radius ;} cone_area_fraction() const152 double cone_area_fraction () const {return _cone_area_fraction ;} max_pair_size() const153 int max_pair_size () const {return _max_pair_size ;} max_iterations() const154 int max_iterations () const {return _max_iterations ;} overlap_threshold() const155 double overlap_threshold () const {return _overlap_threshold ;} 156 157 158 // the things that are required by base class 159 virtual std::string description () const; 160 virtual void run_clustering(ClusterSequence &) const; 161 /// the plugin mechanism's standard way of accessing the jet radius R() const162 virtual double R() const {return cone_radius();} 163 164 private: 165 166 double _seed_threshold ; 167 double _cone_radius ; 168 double _cone_area_fraction; 169 int _max_pair_size ; 170 int _max_iterations ; 171 double _overlap_threshold ; 172 SplitMergeScale _sm_scale ; 173 174 static bool _first_time; 175 176 /// print a banner for reference to the 3rd-party code 177 void _print_banner(std::ostream *ostr) const; 178 }; 179 180 FASTJET_END_NAMESPACE // defined in fastjet/internal/base.hh 181 182 #endif // __CDFMIDPOINTPLUGIN_HH__ 183