/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_5_3_13_patch3/src/RecoTracker/SpecialSeedGenerators/src/CosmicSeedCreator.cc

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#include "RecoTracker/SpecialSeedGenerators/interface/CosmicSeedCreator.h"
#include "RecoTracker/TkTrackingRegions/interface/TrackingRegion.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "MagneticField/Records/interface/IdealMagneticFieldRecord.h"
#include "FWCore/Framework/interface/ESHandle.h"
#include "TrackingTools/TrajectoryState/interface/TrajectoryStateTransform.h"
#include "TrackingTools/TrajectoryState/interface/TrajectoryStateOnSurface.h"
#include "RecoTracker/TkSeedingLayers/interface/SeedComparitor.h"

template <class T> T sqr( T t) {return t*t;}

const TrajectorySeed * CosmicSeedCreator::trajectorySeed(TrajectorySeedCollection & seedCollection,
                                                         const SeedingHitSet & ordered,
                                                         const TrackingRegion & region,
                                                         const edm::EventSetup& es,
                                                         const SeedComparitor *filter)
{

  //_________________________
  //
  //Get Parameters
  //________________________


  //hit package
  //+++++++++++
  const SeedingHitSet & hits = ordered; 
  if ( hits.size() < 2) return 0;


  //hits
  //++++
  TransientTrackingRecHit::ConstRecHitPointer tth1 = hits[0];
  TransientTrackingRecHit::ConstRecHitPointer tth2 = hits[1];

  TransientTrackingRecHit::ConstRecHitPointer usedHit;

  //definition of position & momentum
  //++++++++++++++++++++++++++++++++++
  GlobalVector initialMomentum(region.direction());//direction of the trajectory seed given by the direction of the region
  //fix the momentum scale
  //initialMomentum = initialMomentum.basicVector.unitVector() * region.origin().direction().mag();
  //initialMomentum = region.origin().direction(); //alternative.
  LogDebug("CosmicSeedCreator") << "initial momentum = " << initialMomentum;


  //magnetic field
  //++++++++++++++
  edm::ESHandle<MagneticField> bfield;
  es.get<IdealMagneticFieldRecord>().get(bfield);

  
  //___________________________________________
  //
  //Direction of the trajectory seed
  //___________________________________________


  //radius
  //++++++
  bool reverseAll = false;
  if ( fabs(tth1->globalPosition().perp()) < fabs(tth2->globalPosition().perp()) )  
    //comparison of the position of the 2 hits by checking/comparing their radius
    {
      usedHit=tth1;
      reverseAll = true;
    }

  else usedHit=tth2;


  //location in the barrel (up or bottom)
  //+++++++++++++++++++++++++++++++++++++
  //simple check, probably nees to be more precise FIXME
  bool bottomSeed = (usedHit->globalPosition().y()<0);
          

  //apply corrections
  //+++++++++++++++++
  edm::OwnVector<TrackingRecHit> seedHits;

  if (reverseAll){
    LogDebug("CosmicSeedCreator") <<"Reverse all applied";

    seedHits.push_back(tth2->hit()->clone());
    seedHits.push_back(tth1->hit()->clone());
  }

  else {
    seedHits.push_back(tth1->hit()->clone());
    seedHits.push_back(tth2->hit()->clone());
  }

  
  //propagation
  //+++++++++++

  PropagationDirection seedDirection = alongMomentum; //by default

  
  if (reverseAll) initialMomentum *=-1; 

  if (bottomSeed){
    //means that the seed parameters are inverse of what we want.
    //reverse the momentum again
    initialMomentum *=-1;
    //and change the direction of the seed
    seedDirection = oppositeToMomentum;
  }
  

  for (int charge=-1;charge<=1;charge+=2){
    //fixme, what hit do you want to use ?
    
    FreeTrajectoryState freeState(GlobalTrajectoryParameters(usedHit->globalPosition(),
                                                             initialMomentum, charge, &*bfield),
                                  CurvilinearTrajectoryError(ROOT::Math::SMatrixIdentity())
                                  );

    LogDebug("CosmicSeedCreator")<<"Position freeState: " << usedHit->globalPosition()
                                 <<"\nCharge: "<< charge
                                 <<"\nInitial momentum :" << initialMomentum ;

    TrajectoryStateOnSurface tsos(freeState, *usedHit->surface());
    
    
    PTrajectoryStateOnDet const & PTraj = trajectoryStateTransform::persistentState(tsos, usedHit->hit()->geographicalId().rawId());
    TrajectorySeed seed(PTraj,seedHits,seedDirection);
    if (filter == 0 || filter->compatible(seed)) {
        seedCollection.push_back(seed);
    }
    
  }//end charge loop
  
  
  //________________
  //
  //Return seed
  //________________

    
  LogDebug("CosmicSeedCreator") 
    << "Using SeedCreator---------->\n"
    << "seedCollections size = " << seedCollection.size();
  
  if ( seedCollection.size() > maxseeds_ ) {
    edm::LogError("TooManySeeds") << "Found too many seeds (" << seedCollection.size() << " > " << maxseeds_ << "), bailing out.\n";
    seedCollection.clear();
    return 0;
  }
  else {
    return (seedCollection.empty() ? 0 : &seedCollection.back());
  }
  
}