1 #ifndef __SISCONESPHERICALPLUGIN_HH__
2 #define __SISCONESPHERICALPLUGIN_HH__
4 #include "SISConeBasePlugin.hh"
6 // forward declaration of the siscone classes we'll need
7 namespace siscone_spherical{
11 // questionable whether this should be in fastjet namespace or not...
12 namespace fastjet { // defined in fastjet/internal/base.hh
14 //----------------------------------------------------------------------
16 /// SISConeSphericalPlugin is a plugin for fastjet (v2.1 upwards) that
17 /// provides an interface to the seedless infrared safe cone jet
18 /// finder by Gregory Soyez and Gavin Salam.
20 /// This is the version of SISCone using spherical coordinates. Compared
21 /// to the original cylindrical version:
23 /// - Particles are within a cone if their opening angle relative to the
24 /// centre of the cone is less than R
26 /// - The split-merge step uses the total energy in the protojet as the
27 /// ordering and overlap-measure variable
29 /// - The IR safety of the split-merge step is _not_ guaranteed for
30 /// events consisting of two back-to-back identical heavy particles
31 /// that decay. This is because of potential degeneracies in the
32 /// ordering for the split-merge step.
34 /// For moderate values of R the problem should not be too severe
35 /// (or may even be absent for some values of the overlap
36 /// parameter), however the user should be aware of the issue.
38 /// The default split-merge scale may change at a later date to
39 /// resolve this issue.
42 /// SISCone uses geometrical techniques to exhaustively consider all
43 /// possible distinct cones. It then finds out which ones are stable
44 /// and sends the result to the Tevatron Run-II type split-merge
45 /// procedure for overlapping cones.
47 /// Four parameters govern the "physics" of the algorithm:
49 /// - the cone_radius (this should be self-explanatory!)
51 /// - the overlap_threshold is the parameter which dictates how much
52 /// two jets must overlap (E_overlap/min(E1,E2)) if they are to be
55 /// - Not all particles are in stable cones in the first round of
56 /// searching for stable cones; one can therefore optionally have the
57 /// the jet finder carry out additional passes of searching for
58 /// stable cones among particles that were in no stable cone in
59 /// previous passes --- the maximum number of passes carried out is
60 /// n_pass_max. If this is zero then additional passes are carried
61 /// out until no new stable cones are found.
63 /// - Protojet Emin: protojets that are below this Emin
64 /// (default = 0) are discarded before each iteration of the
67 /// One parameter governs some internal algorithmic shortcuts:
69 /// - if "caching" is turned on then the last event clustered by
70 /// siscone is stored -- if the current event is identical and the
71 /// cone_radius and n_pass_max are identical, then the only part of
72 /// the clustering that needs to be rerun is the split-merge part,
73 /// leading to significant speed gains; there is a small (O(N) storage
74 /// and speed) penalty for caching, so it should be kept off
75 /// (default) if only a single overlap_threshold is used.
77 /// The final jets can be accessed by requestion the
78 /// inclusive_jets(...) from the ClusterSequence object. Note that
79 /// these PseudoJets have their user_index() set to the index of the
80 /// pass in which they were found (first pass = 0). NB: This does not
81 /// currently work for jets that consist of a single particle.
83 /// For further information on the details of the algorithm see the
84 /// SISCone paper, arXiv:0704.0292 [JHEP 0705:086,2007].
86 /// For documentation about the implementation, see the
87 /// siscone/doc/html/index.html file.
89 class SISConeSphericalPlugin : public SISConeBasePlugin{
92 /// enum for the different split-merge scale choices;
93 /// Note that order _must_ be the same as in siscone
94 enum SplitMergeScale {SM_E, ///< Energy (IR unsafe with momentum conservation)
95 SM_Etilde ///< sum_{i \in jet} E_i [1+sin^2(theta_iJ)]
99 /// Main constructor for the SISConeSpherical Plugin class.
102 SISConeSphericalPlugin (double cone_radius,
103 double overlap_threshold,
105 double protojet_Emin = 0.0,
106 bool caching = false,
107 SplitMergeScale split_merge_scale = SM_Etilde,
108 double split_merge_stopping_scale = 0.0){
109 _cone_radius =cone_radius;
110 _overlap_threshold =overlap_threshold;
111 _n_pass_max =n_pass_max;
112 _protojet_Emin =protojet_Emin;
114 _split_merge_scale =split_merge_scale;
115 _split_merge_stopping_scale = split_merge_stopping_scale;
116 _ghost_sep_scale = 0.0;
117 _use_E_weighted_splitting = false;
120 /// minimum energy for a protojet to be considered in the split-merge step
122 double protojet_Emin () const {return _protojet_Emin ;}
124 /// return the scale to be passed to SISCone as the protojet_Emin
125 /// -- if we have a ghost separation scale that is above the
126 /// protojet_ptmin, then the ghost_separation_scale becomes the
127 /// relevant one to use here
128 double protojet_or_ghost_Emin () const {return std::max(_protojet_Emin,
131 /// indicates scale used in split-merge
132 SplitMergeScale split_merge_scale() const {return _split_merge_scale;}
133 /// sets scale used in split-merge
134 void set_split_merge_scale(SplitMergeScale sms) {_split_merge_scale = sms;}
136 /// indicate if the splittings are done using the anti-kt distance
137 bool split_merge_use_E_weighted_splitting() const {return _use_E_weighted_splitting;}
138 void set_split_merge_use_E_weighted_splitting(bool val) {
139 _use_E_weighted_splitting = val;}
141 /// overload the default as we don't provide support
142 /// for passive areas.
143 virtual bool supports_ghosted_passive_areas() const {return true;}
145 // the things that are required by base class
146 virtual std::string description () const;
147 virtual void run_clustering(ClusterSequence &) const ;
150 virtual void reset_stored_plugin() const;
153 double _protojet_Emin;
154 SplitMergeScale _split_merge_scale;
155 bool _use_E_weighted_splitting;
157 // part needed for the cache
158 // variables for caching the results and the input
159 static std::auto_ptr<SISConeSphericalPlugin > stored_plugin;
160 static std::auto_ptr<std::vector<PseudoJet> > stored_particles;
161 static std::auto_ptr<siscone_spherical::CSphsiscone> stored_siscone;
164 //======================================================================
165 /// Class that provides extra information about a SISCone clustering
166 class SISConeSphericalExtras : public SISConeBaseExtras {
169 // it just initialises the pass information
170 SISConeSphericalExtras(int nparticles)
171 : SISConeBaseExtras(nparticles){}
173 /// access to the siscone jet def plugin (more convenient than
174 /// getting it from the original jet definition, because here it's
175 /// directly of the right type (rather than the base type)
176 const SISConeSphericalPlugin* jet_def_plugin() const {
177 return dynamic_cast<const SISConeSphericalPlugin*>(_jet_def_plugin);
181 // let us be written to by SISConePlugin
182 friend class SISConeSphericalPlugin;
185 } // fastjet namespace
187 #endif // __SISCONEPLUGIN_HH__