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fastjet::CDFMidPointPlugin Class Reference

CDFMidPointPlugin is a plugin for fastjet (v2.1 upwards) that provides an interface to the CDF version of Run-II iterative cone algorithm with midpoint seeds (also known as the Iterative Legacy Cone Algorithm, ILCA). More...

#include <CDFMidPointPlugin.hh>

Inheritance diagram for fastjet::CDFMidPointPlugin:

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List of all members.

Public Types

enum  SplitMergeScale { SM_pt, SM_Et, SM_mt }
 the choice of scale to be used in the split-merge step More...

Public Member Functions

 CDFMidPointPlugin (double seed_threshold, double cone_radius, double cone_area_fraction, int max_pair_size, int max_iterations, double overlap_threshold, SplitMergeScale sm_scale=SM_pt)
 A CDFMidPointPlugin constructor that looks like the one provided by CDF.
 CDFMidPointPlugin (double cone_radius, double overlap_threshold=0.5, double seed_threshold=1.0, double cone_area_fraction=1.0)
 a compact constructor
double seed_threshold () const
double cone_radius () const
double cone_area_fraction () const
int max_pair_size () const
int max_iterations () const
double overlap_threshold () const
virtual std::string description () const
 return a textual description of the jet-definition implemented in this plugin
virtual void run_clustering (ClusterSequence &) const
 given a ClusterSequence that has been filled up with initial particles, the following function should fill up the rest of the ClusterSequence, using the following member functions of ClusterSequence:
  • plugin_do_ij_recombination(.


Private Attributes

double _seed_threshold
double _cone_radius
double _cone_area_fraction
int _max_pair_size
int _max_iterations
double _overlap_threshold
SplitMergeScale _sm_scale

Detailed Description

CDFMidPointPlugin is a plugin for fastjet (v2.1 upwards) that provides an interface to the CDF version of Run-II iterative cone algorithm with midpoint seeds (also known as the Iterative Legacy Cone Algorithm, ILCA).

The CDF code has been taken from Joey Huston's webpage http://www.pa.msu.edu/~huston/Les_Houches_2005/Les_Houches_SM.html

Note that the CDF midpoint code contains options that go beyond those described in the Tevatron run-II document (hep-ex/0005012), notably search-cones, as described in hep-ph/0111434, and midpoints bewteen multiplets of stable cones.

Additionally, the version of the CDF midpoint code distributed here has been modified by the FastJet authors, so as to allow one to choose the scale used in the split-merge step.

Definition at line 60 of file CDFMidPointPlugin.hh.


Member Enumeration Documentation

enum fastjet::CDFMidPointPlugin::SplitMergeScale
 

the choice of scale to be used in the split-merge step

Enumeration values:
SM_pt 
SM_Et 
SM_mt 

Definition at line 64 of file CDFMidPointPlugin.hh.

00064 {SM_pt, SM_Et, SM_mt};


Constructor & Destructor Documentation

fastjet::CDFMidPointPlugin::CDFMidPointPlugin double  seed_threshold,
double  cone_radius,
double  cone_area_fraction,
int  max_pair_size,
int  max_iterations,
double  overlap_threshold,
SplitMergeScale  sm_scale = SM_pt
[inline]
 

A CDFMidPointPlugin constructor that looks like the one provided by CDF.

Its arguments should have the following meaning:

  • seed_threshold: minimum pt for a particle to be considered a seed of the iteration.

  • cone_radius: standard meaning

  • cone_area_fraction: stable-cones are searched for with a radius Rsearch = R * sqrt(cone_area_fraction), and then expanded to size R afterwards; note (hep-ph/0610012) that this introduces IR unsafety at NLO for X+2-jet observables (where X any hard object).

  • max_pair_size: "midpoints" can be added between pairs of stable cones, triplets of stable cones, etc.; max_pair_size indicates the maximum number of stable cones that are assembled when adding midpoints.

  • max_iterations: the maximum number of iterations to carry out when looking for a stable cone.

  • overlap_threshold: if (overlapping_Et)/(Et_of_softer_protojet) < overlap_threshold, overlapping jets are split, otherwise they are merged.

  • sm_scale: a choice for the scale to be used in the split-merge step (both for ordering the momenta and quantifying the overlap); the three options are

. SM_pt: pt (default -- source of small IR safety issue in purely hadronic events)

. SM_Et: Et (not boost invariant, reduces to mt at zero rapidity and to pt and infinite rapidity)

. SM_mt: transverse mass = sqrt(m^2+pt^2)

Definition at line 105 of file CDFMidPointPlugin.hh.

fastjet::CDFMidPointPlugin::CDFMidPointPlugin double  cone_radius,
double  overlap_threshold = 0.5,
double  seed_threshold = 1.0,
double  cone_area_fraction = 1.0
[inline]
 

a compact constructor

Definition at line 122 of file CDFMidPointPlugin.hh.


Member Function Documentation

double fastjet::CDFMidPointPlugin::cone_area_fraction  )  const [inline]
 

Definition at line 138 of file CDFMidPointPlugin.hh.

Referenced by description().

00138 {return _cone_area_fraction ;}

double fastjet::CDFMidPointPlugin::cone_radius  )  const [inline]
 

Definition at line 137 of file CDFMidPointPlugin.hh.

Referenced by description().

00137 {return _cone_radius        ;}

string fastjet::CDFMidPointPlugin::description  )  const [virtual]
 

return a textual description of the jet-definition implemented in this plugin

Implements fastjet::JetDefinition::Plugin.

Definition at line 45 of file CDFMidPointPlugin.cc.

References _sm_scale, cone_area_fraction(), cone_radius(), max_iterations(), max_pair_size(), overlap_threshold(), seed_threshold(), SM_Et, SM_mt, and SM_pt.

00045                                              {
00046   ostringstream desc;
00047   
00048   string sm_scale_string = "split-merge uses ";
00049   switch(_sm_scale) {
00050   case SM_pt:
00051     sm_scale_string += "pt";
00052     break;
00053   case SM_Et:
00054     sm_scale_string += "Et";
00055     break;
00056   case SM_mt:
00057     sm_scale_string += "mt";
00058     break;
00059   default:
00060     ostringstream err;
00061     err << "Unrecognized split-merge scale choice = " << _sm_scale;
00062     throw Error(err.str());
00063   }
00064 
00065   desc << "CDF MidPoint jet finder with " 
00066        << "seed_threshold = "     << seed_threshold     () << ", "
00067        << "cone_radius = "        << cone_radius        () << ", "
00068        << "cone_area_fraction = " << cone_area_fraction () << ", " 
00069        << "max_pair_size = "      << max_pair_size      () << ", "
00070        << "max_iterations = "     << max_iterations     () << ", "
00071        << "overlap_threshold  = " << overlap_threshold  () << ", "
00072        << sm_scale_string ;
00073 
00074   return desc.str();
00075 }

int fastjet::CDFMidPointPlugin::max_iterations  )  const [inline]
 

Definition at line 140 of file CDFMidPointPlugin.hh.

Referenced by description().

00140 {return _max_iterations     ;}

int fastjet::CDFMidPointPlugin::max_pair_size  )  const [inline]
 

Definition at line 139 of file CDFMidPointPlugin.hh.

Referenced by description().

00139 {return _max_pair_size      ;}

double fastjet::CDFMidPointPlugin::overlap_threshold  )  const [inline]
 

Definition at line 141 of file CDFMidPointPlugin.hh.

Referenced by description().

00141 {return _overlap_threshold  ;}

void fastjet::CDFMidPointPlugin::run_clustering ClusterSequence  )  const [virtual]
 

given a ClusterSequence that has been filled up with initial particles, the following function should fill up the rest of the ClusterSequence, using the following member functions of ClusterSequence:

  • plugin_do_ij_recombination(.

..)

  • plugin_do_iB_recombination(...)

Implements fastjet::JetDefinition::Plugin.

Definition at line 78 of file CDFMidPointPlugin.cc.

References _cone_area_fraction, _cone_radius, _max_iterations, _max_pair_size, _overlap_threshold, _seed_threshold, _sm_scale, fastjet::ClusterSequence::jets(), fastjet::ClusterSequence::plugin_record_iB_recombination(), and fastjet::ClusterSequence::plugin_record_ij_recombination().

00078                                                                         {
00079  
00080   // create the physics towers needed by the CDF code
00081   vector<PhysicsTower> towers;
00082   towers.reserve(clust_seq.jets().size());
00083   for (unsigned i = 0; i < clust_seq.jets().size(); i++) {
00084     LorentzVector fourvect(clust_seq.jets()[i].px(),
00085                            clust_seq.jets()[i].py(),
00086                            clust_seq.jets()[i].pz(),
00087                            clust_seq.jets()[i].E());
00088     PhysicsTower tower(fourvect);
00089     // misuse one of the indices for tracking, since the MidPoint
00090     // implementation doesn't seem to make use of these indices
00091     tower.calTower.iEta = i;
00092     towers.push_back(tower);
00093   }
00094 
00095   // prepare the CDF algorithm
00096   MidPointAlgorithm m(_seed_threshold,_cone_radius,_cone_area_fraction,
00097                       _max_pair_size,_max_iterations,_overlap_threshold,
00098                       MidPointAlgorithm::SplitMergeScale(_sm_scale));
00099     
00100   // run the CDF algorithm
00101   std::vector<Cluster> jets;
00102   m.run(towers,jets);
00103 
00104 
00105   // now transfer the jets back into our own structure -- we will
00106   // mimic the cone code with a sequential recombination sequence in
00107   // which the jets are built up by adding one particle at a time
00108   for(vector<Cluster>::const_iterator jetIter = jets.begin(); 
00109                                       jetIter != jets.end(); jetIter++) {
00110     const vector<PhysicsTower> & tower_list = jetIter->towerList;
00111     int jet_k = tower_list[0].calTower.iEta;
00112   
00113     int ntow = int(jetIter->towerList.size());
00114     for (int itow = 1; itow < ntow; itow++) {
00115       int jet_i = jet_k;
00116       // retrieve our misappropriated index for the jet
00117       int jet_j = tower_list[itow].calTower.iEta;
00118       // do a fake recombination step with dij=0
00119       double dij = 0.0;
00120       clust_seq.plugin_record_ij_recombination(jet_i, jet_j, dij, jet_k);
00121     }
00122   
00123     // NB: put a sensible looking d_iB just to be nice...
00124     double d_iB = clust_seq.jets()[jet_k].perp2();
00125     clust_seq.plugin_record_iB_recombination(jet_k, d_iB);
00126   }
00127 
00128 
00129   // following code is for testing only
00130   //cout << endl;
00131   //for(vector<Cluster>::const_iterator jetIter = jets.begin(); 
00132   //                                    jetIter != jets.end(); jetIter++) {
00133   //  cout << jetIter->fourVector.pt() << " " << jetIter->fourVector.y() << endl;
00134   //}
00135   //cout << "-----------------------------------------------------\n";
00136   //vector<PseudoJet> ourjets(clust_seq.inclusive_jets());
00137   //for (vector<PseudoJet>::const_reverse_iterator ourjet = ourjets.rbegin();
00138   //     ourjet != ourjets.rend(); ourjet++) {
00139   //  cout << ourjet->perp() << " " << ourjet->rap() << endl;
00140   //}
00141   //cout << endl;
00142 }

double fastjet::CDFMidPointPlugin::seed_threshold  )  const [inline]
 

Definition at line 136 of file CDFMidPointPlugin.hh.

Referenced by description().

00136 {return _seed_threshold     ;}


Member Data Documentation

double fastjet::CDFMidPointPlugin::_cone_area_fraction [private]
 

Definition at line 152 of file CDFMidPointPlugin.hh.

Referenced by run_clustering().

double fastjet::CDFMidPointPlugin::_cone_radius [private]
 

Definition at line 151 of file CDFMidPointPlugin.hh.

Referenced by run_clustering().

int fastjet::CDFMidPointPlugin::_max_iterations [private]
 

Definition at line 154 of file CDFMidPointPlugin.hh.

Referenced by run_clustering().

int fastjet::CDFMidPointPlugin::_max_pair_size [private]
 

Definition at line 153 of file CDFMidPointPlugin.hh.

Referenced by run_clustering().

double fastjet::CDFMidPointPlugin::_overlap_threshold [private]
 

Definition at line 155 of file CDFMidPointPlugin.hh.

Referenced by run_clustering().

double fastjet::CDFMidPointPlugin::_seed_threshold [private]
 

Definition at line 150 of file CDFMidPointPlugin.hh.

Referenced by run_clustering().

SplitMergeScale fastjet::CDFMidPointPlugin::_sm_scale [private]
 

Definition at line 156 of file CDFMidPointPlugin.hh.

Referenced by description(), and run_clustering().


The documentation for this class was generated from the following files:
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