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 #ifndef __SISCONESPHERICALPLUGIN_HH__
 #define __SISCONESPHERICALPLUGIN_HH__
 
 #include "SISConeBasePlugin.hh"
 
 // forward declaration of the siscone classes we'll need
 namespace siscone_spherical{
   class CSphsiscone;
 }
 
 // questionable whether this should be in fastjet namespace or not...
 FASTJET_BEGIN_NAMESPACE      // defined in fastjet/internal/base.hh
 
 //----------------------------------------------------------------------
 //
 /// @ingroup plugins
 /// \class SISConeSphericalPlugin
 /// Implementation of the spherical version of the SISCone algorithm
 /// (plugin for fastjet v2.1 upwards)
 ///
 /// SISConeSphericalPlugin is a plugin for fastjet (v2.1 upwards) that
 /// provides an interface to the seedless infrared safe cone jet
 /// finder by Gregory Soyez and Gavin Salam.
 ///
 /// This is the version of SISCone using spherical coordinates. Compared
 /// to the original cylindrical version:
 ///
 ///  - Particles are within a cone if their opening angle relative to the
 ///    centre of the cone is less than R
 ///
 ///  - The split-merge step uses the total energy in the protojet as the
 ///    ordering and overlap-measure variable
 ///
 ///  - The IR safety of the split-merge step is _not_ guaranteed for
 ///    events consisting of two back-to-back identical heavy particles
 ///    that decay. This is because of potential degeneracies in the
 ///    ordering for the split-merge step. 
 ///
 ///    For moderate values of R the problem should not be too severe
 ///    (or may even be absent for some values of the overlap
 ///    parameter), however the user should be aware of the issue.
 ///
 ///    The default split-merge scale may change at a later date to
 ///    resolve this issue.
 ///
 ///
 /// SISCone uses geometrical techniques to exhaustively consider all
 /// possible distinct cones. It then finds out which ones are stable
 /// and sends the result to the Tevatron Run-II type split-merge
 /// procedure for overlapping cones.
 ///
 /// Four parameters govern the "physics" of the algorithm:
 ///
 ///  - the cone_radius (this should be self-explanatory!)
 ///
 ///  - the overlap_threshold is the parameter which dictates how much
 ///    two jets must overlap (E_overlap/min(E1,E2)) if they are to be 
 ///    merged
 ///
 ///  - Not all particles are in stable cones in the first round of
 ///    searching for stable cones; one can therefore optionally have the
 ///    the jet finder carry out additional passes of searching for
 ///    stable cones among particles that were in no stable cone in
 ///    previous passes --- the maximum number of passes carried out is
 ///    n_pass_max. If this is zero then additional passes are carried
 ///    out until no new stable cones are found.
 ///
 ///  - Protojet Emin: protojets that are below this Emin
 ///    (default = 0) are discarded before each iteration of the
 ///    split-merge loop.
 ///
 /// One parameter governs some internal algorithmic shortcuts: 
 ///
 /// - if "caching" is turned on then the last event clustered by
 ///   siscone is stored -- if the current event is identical and the
 ///   cone_radius and n_pass_max are identical, then the only part of
 ///   the clustering that needs to be rerun is the split-merge part,
 ///   leading to significant speed gains; there is a small (O(N) storage
 ///   and speed) penalty for caching, so it should be kept off
 ///   (default) if only a single overlap_threshold is used.
 ///
 /// The final jets can be accessed by requestion the
 /// inclusive_jets(...) from the ClusterSequence object. Note that
 /// these PseudoJets have their user_index() set to the index of the
 /// pass in which they were found (first pass = 0). NB: This does not
 /// currently work for jets that consist of a single particle.
 ///
 /// For further information on the details of the algorithm see the
 /// SISCone paper, arXiv:0704.0292 [JHEP 0705:086,2007].
 ///
 /// For documentation about the implementation, see the
 /// siscone/doc/html/index.html file.
 //
 class SISConeSphericalPlugin : public SISConeBasePlugin{
 public:
 
   /// enum for the different split-merge scale choices;
   /// Note that order _must_ be the same as in siscone
   enum SplitMergeScale {SM_E,        ///< Energy (IR unsafe with momentum conservation)
             SM_Etilde    ///< sum_{i \in jet} E_i [1+sin^2(theta_iJ)]
   };
 
 
   /// Main constructor for the SISConeSpherical Plugin class.  
   ///
   ///
   SISConeSphericalPlugin (double cone_radius_in,
               double overlap_threshold_in,
               int    n_pass_max_in = 0,
               double protojet_Emin_in = 0.0, 
               bool   caching_in = false,
               SplitMergeScale  split_merge_scale_in = SM_Etilde,
               double split_merge_stopping_scale_in = 0.0){
     _cone_radius           =cone_radius_in;
     _overlap_threshold     =overlap_threshold_in;
     _n_pass_max            =n_pass_max_in;
     _protojet_Emin         =protojet_Emin_in;
     _caching               =caching_in;
     _split_merge_scale     =split_merge_scale_in;
     _split_merge_stopping_scale = split_merge_stopping_scale_in;
     _ghost_sep_scale       = 0.0;
     _use_E_weighted_splitting = false;
   }
 
   /// minimum energy for a protojet to be considered in the split-merge step
   /// of the algorithm
   double protojet_Emin  () const {return _protojet_Emin  ;}
 
   /// return the scale to be passed to SISCone as the protojet_Emin
   /// -- if we have a ghost separation scale that is above the
   /// protojet_ptmin, then the ghost_separation_scale becomes the
   /// relevant one to use here
   double protojet_or_ghost_Emin  () const {return std::max(_protojet_Emin,
                                                            _ghost_sep_scale);}
 
   /// indicates scale used in split-merge
   SplitMergeScale split_merge_scale() const {return _split_merge_scale;}
   /// sets scale used in split-merge
   void set_split_merge_scale(SplitMergeScale sms) {_split_merge_scale = sms;}
 
   /// indicate if the splittings are done using the anti-kt distance
   bool split_merge_use_E_weighted_splitting() const {return _use_E_weighted_splitting;}
   void set_split_merge_use_E_weighted_splitting(bool val) {
     _use_E_weighted_splitting = val;}
 
   /// overload the default as we don't provide support 
   /// for passive areas.
   virtual bool supports_ghosted_passive_areas() const {return true;}
   
   // the things that are required by base class
   virtual std::string description () const;
   virtual void run_clustering(ClusterSequence &) const ;
 
   /// returns true because this plugin is intended for spherical
   /// geometries (i.e. it's an e+e- algorithm).
   virtual bool is_spherical() const {return true;}
 
 protected:
   virtual void reset_stored_plugin() const;
 
 private:
   double _protojet_Emin;
   SplitMergeScale _split_merge_scale;
   bool _use_E_weighted_splitting;
 
   // part needed for the cache 
   // variables for caching the results and the input
   static SharedPtr<SISConeSphericalPlugin        > stored_plugin;
   static SharedPtr<std::vector<PseudoJet>        > stored_particles;
   static SharedPtr<siscone_spherical::CSphsiscone> stored_siscone;
 };
 
 //======================================================================
 /// @ingroup extra_info
 /// \class SISConeSphericalExtras
 /// Class that provides extra information about a SISCone clustering
 class SISConeSphericalExtras : public SISConeBaseExtras {
 public:
   /// constructor
   //  it just initialises the pass information 
   SISConeSphericalExtras(int nparticles)
     : SISConeBaseExtras(nparticles){}
 
   /// access to the siscone jet def plugin (more convenient than
   /// getting it from the original jet definition, because here it's
   /// directly of the right type (rather than the base type)
   const SISConeSphericalPlugin* jet_def_plugin() const {
     return dynamic_cast<const SISConeSphericalPlugin*>(_jet_def_plugin);
   }
 
 private:
   // let us be written to by SISConePlugin
   friend class SISConeSphericalPlugin;
 };
 
 FASTJET_END_NAMESPACE        // defined in fastjet/internal/base.hh
 
 #endif // __SISCONEPLUGIN_HH__
 

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