CMSIterativeConeAlgorithm Class Reference

#include <CMSIterativeConeAlgorithm.h>

Public Member Functions
	CMSIterativeConeAlgorithm (double seed, double radius)
void	run (const JetReco::InputCollection &fInput, JetReco::OutputCollection *fOutput) const
	Find the ProtoJets from the collection of input Candidates. More...

Private Attributes
double	theConeRadius
double	theSeedThreshold

Detailed Description

CMSIterativeConeAlgorithm - iterative cone algorithm without jet merging/splitting. Originally implemented in ORCA by H.P.Wellish. Documented in CMS NOTE-2006/036

Author

A.Ulyanov, ITEP

Definition at line 18 of file CMSIterativeConeAlgorithm.h.

Constructor & Destructor Documentation

CMSIterativeConeAlgorithm::CMSIterativeConeAlgorithm ( double  seed, double  radius  )

inline

Constructor

Parameters

seed	defines the minimum ET in GeV of a tower that can seed a jet.
radius	defines the maximum radius of a jet in eta-phi space.

Definition at line 24 of file CMSIterativeConeAlgorithm.h.

                                                       : 
    theSeedThreshold(seed),
    theConeRadius(radius)
    { }

Member Function Documentation

void CMSIterativeConeAlgorithm::run	(	const JetReco::InputCollection &	fInput,
		JetReco::OutputCollection *	fOutput
	)		const

Find the ProtoJets from the collection of input Candidates.

Definition at line 19 of file CMSIterativeConeAlgorithm.cc.

References Geom::deltaR2(), reco::Candidate::et(), reco::Candidate::eta(), eta(), input, align_cfg::iteration, M_PI, phi, reco::Candidate::phi(), and python.multivaluedict::sort().

                                                                                                  {
  if (!fOutput) return;
  //make a list of input objects ordered by ET
  list<InputItem> input;
  for (InputCollection::const_iterator towerIter = fInput.begin();
       towerIter != fInput.end(); ++towerIter) {
    input.push_back(*towerIter);
  }   
  GreaterByEtRef <InputItem> compCandidate;
  input.sort(compCandidate);

  //find jets
  while( !input.empty() && input.front()->et() > theSeedThreshold ) {
    //cone centre 
    double eta0=input.front()->eta();
    double phi0=input.front()->phi();
    //protojet properties
    double eta=0;
    double phi=0;
    double et=0;
    //list of towers in cone
    list< list<InputItem>::iterator> cone;
    for(int iteration=0;iteration<100;iteration++){
      cone.clear();
      eta=0;
      phi=0;
      et=0;
      for(list<InputItem>::iterator inp=input.begin();
      inp!=input.end();inp++){
    InputItem tower = *inp; 
    if( deltaR2(eta0,phi0,tower->eta(),tower->phi()) < 
        theConeRadius*theConeRadius) {
          cone.push_back(inp);
          eta+= tower->et()*tower->eta();
          double dphi=tower->phi()-phi0;
          if(dphi>M_PI) dphi-=2*M_PI;
          else if(dphi<=-M_PI) dphi+=2*M_PI;
          phi+=tower->et()*dphi;
          et +=tower->et();
        }
      }
      eta=eta/et;
      phi=phi0+phi/et;
      if(phi>M_PI)phi-=2*M_PI;
      else if(phi<=-M_PI)phi+=2*M_PI;
      
      if(fabs(eta-eta0)<.001 && fabs(phi-phi0)<.001) break;//stable cone found
      eta0=eta;
      phi0=phi;
    }

    //make a final jet and remove the jet constituents from the input list 
    InputCollection jetConstituents;     
    list< list<InputItem>::iterator>::const_iterator inp;
    for(inp=cone.begin();inp!=cone.end();inp++)  {
      jetConstituents.push_back(**inp);
      input.erase(*inp);
    }
    fOutput->push_back (ProtoJet (jetConstituents));

  } //loop over seeds ended
  GreaterByPt<ProtoJet> compJets;
  sort (fOutput->begin (), fOutput->end (), compJets);
}

Member Data Documentation

double CMSIterativeConeAlgorithm::theConeRadius

private

Definition at line 35 of file CMSIterativeConeAlgorithm.h.

double CMSIterativeConeAlgorithm::theSeedThreshold

private

Definition at line 34 of file CMSIterativeConeAlgorithm.h.