2 // $Id: CDFMidPointPlugin.hh 1186 2008-04-04 16:15:39Z salam $
4 // Copyright (c) 2005-2006, Matteo Cacciari and Gavin Salam
6 //----------------------------------------------------------------------
7 // This file is part of FastJet.
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.
14 // The algorithms that underlie FastJet have required considerable
15 // development and are described in hep-ph/0512210. If you use
16 // FastJet as part of work towards a scientific publication, please
17 // include a citation to the FastJet paper.
19 // FastJet is distributed in the hope that it will be useful,
20 // but WITHOUT ANY WARRANTY; without even the implied warranty of
21 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 // GNU General Public License for more details.
24 // You should have received a copy of the GNU General Public License
25 // along with FastJet; if not, write to the Free Software
27 // 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
28 //----------------------------------------------------------------------
31 #ifndef __CDFMIDPOINTPLUGIN_HH__
32 #define __CDFMIDPOINTPLUGIN_HH__
34 #include "fastjet/JetDefinition.hh"
36 // questionable whether this should be in fastjet namespace or not...
38 namespace fastjet { // defined in fastjet/internal/base.hh
40 //----------------------------------------------------------------------
42 /// CDFMidPointPlugin is a plugin for fastjet (v2.1 upwards) that
43 /// provides an interface to the CDF version of Run-II iterative cone
44 /// algorithm with midpoint seeds (also known as the Iterative Legacy
45 /// Cone Algorithm, ILCA).
47 /// The CDF code has been taken from Joey Huston's webpage
48 /// http://www.pa.msu.edu/~huston/Les_Houches_2005/Les_Houches_SM.html
50 /// Note that the CDF midpoint code contains options that go beyond
51 /// those described in the Tevatron run-II document (hep-ex/0005012),
52 /// notably search-cones, as described in hep-ph/0111434, and
53 /// midpoints bewteen multiplets of stable cones.
55 /// Additionally, the version of the CDF midpoint code distributed
56 /// here has been modified by the FastJet authors, so as to allow one
57 /// to choose the scale used in the split-merge step.
59 //----------------------------------------------------------------------
60 class CDFMidPointPlugin : public JetDefinition::Plugin {
62 /// the choice of scale to be used in the split-merge step
63 // NB: just replicates what we've added to the CDF midpoint code
64 enum SplitMergeScale {SM_pt, SM_Et, SM_mt, SM_pttilde};
67 /// A CDFMidPointPlugin constructor that looks like the one provided
68 /// by CDF. Its arguments should have the following meaning:
70 /// - seed_threshold: minimum pt for a particle to be considered
71 /// a seed of the iteration.
73 /// - cone_radius: standard meaning
75 /// - cone_area_fraction: stable-cones are searched for with a
76 /// radius Rsearch = R * sqrt(cone_area_fraction), and then
77 /// expanded to size R afterwards; note (hep-ph/0610012) that this
78 /// introduces IR unsafety at NLO for X+2-jet observables (where X
81 /// - max_pair_size: "midpoints" can be added between pairs of
82 /// stable cones, triplets of stable cones, etc.; max_pair_size
83 /// indicates the maximum number of stable cones that are
84 /// assembled when adding midpoints.
86 /// - max_iterations: the maximum number of iterations to carry out
87 /// when looking for a stable cone.
89 /// - overlap_threshold: if
90 /// (overlapping_Et)/(Et_of_softer_protojet) < overlap_threshold,
91 /// overlapping jets are split, otherwise they are merged.
93 /// - sm_scale: a choice for the scale to be used in the split-merge
94 /// step (both for ordering the momenta and quantifying the
95 /// overlap); the three options are
97 /// . SM_pt: pt (default -- source of small IR safety issue in purely
100 /// . SM_Et: Et (not boost invariant, reduces to mt at zero rapidity and
101 /// to pt and infinite rapidity)
103 /// . SM_mt: transverse mass = sqrt(m^2+pt^2)
106 double seed_threshold ,
108 double cone_area_fraction ,
111 double overlap_threshold ,
112 SplitMergeScale sm_scale = SM_pt) :
113 _seed_threshold (seed_threshold ),
114 _cone_radius (cone_radius ),
115 _cone_area_fraction (cone_area_fraction ),
116 _max_pair_size (max_pair_size ),
117 _max_iterations (max_iterations ),
118 _overlap_threshold (overlap_threshold ),
119 _sm_scale (sm_scale) {}
121 /// a compact constructor
123 /// NB: as of version 2.4, the default value for the
124 /// overlap_threshold threshold has been removed, to avoid
125 /// misleading people into using the value of 0.5 without thinking,
126 /// which is known to have adverse effects in high-noise
127 /// environments. A recommended value is 0.75.
128 CDFMidPointPlugin (double cone_radius,
129 double overlap_threshold,// = 0.5,
130 double seed_threshold = 1.0,
131 double cone_area_fraction = 1.0) :
132 _seed_threshold (seed_threshold ),
133 _cone_radius (cone_radius ),
134 _cone_area_fraction (cone_area_fraction ),
136 _max_iterations (100 ),
137 _overlap_threshold (overlap_threshold ),
141 // some functions to return info about parameters
142 double seed_threshold () const {return _seed_threshold ;}
143 double cone_radius () const {return _cone_radius ;}
144 double cone_area_fraction () const {return _cone_area_fraction ;}
145 int max_pair_size () const {return _max_pair_size ;}
146 int max_iterations () const {return _max_iterations ;}
147 double overlap_threshold () const {return _overlap_threshold ;}
150 // the things that are required by base class
151 virtual std::string description () const;
152 virtual void run_clustering(ClusterSequence &) const;
153 /// the plugin mechanism's standard way of accessing the jet radius
154 virtual double R() const {return cone_radius();}
158 double _seed_threshold ;
159 double _cone_radius ;
160 double _cone_area_fraction;
162 int _max_iterations ;
163 double _overlap_threshold ;
164 SplitMergeScale _sm_scale ;
167 } // fastjet namespace
169 #endif // __CDFMIDPOINTPLUGIN_HH__