SeedFromNuclearInteraction.cc

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#include "RecoTracker/NuclearSeedGenerator/interface/SeedFromNuclearInteraction.h"

#include "Geometry/Records/interface/TrackerDigiGeometryRecord.h"
#include "MagneticField/Engine/interface/MagneticField.h"

#include "TrackingTools/TrajectoryState/interface/TrajectoryStateTransform.h"
#include "TrackingTools/Records/interface/TrackingComponentsRecord.h"
#include "TrackingTools/KalmanUpdators/interface/KFUpdator.h"

#include "FWCore/MessageLogger/interface/MessageLogger.h"


SeedFromNuclearInteraction::SeedFromNuclearInteraction(const Propagator* prop, const TrackerGeometry* geom, const edm::ParameterSet& iConfig):
    ptMin(iConfig.getParameter<double>("ptMin")),
    thePropagator(prop), theTrackerGeom(geom)
    {
         isValid_=true;
         initialTSOS_ = boost::shared_ptr<TrajectoryStateOnSurface>(new TrajectoryStateOnSurface());
         updatedTSOS_ = boost::shared_ptr<TrajectoryStateOnSurface>(new TrajectoryStateOnSurface());
         freeTS_ = boost::shared_ptr<FreeTrajectoryState>(new FreeTrajectoryState());
         pTraj = boost::shared_ptr<PTrajectoryStateOnDet>(new PTrajectoryStateOnDet());
    }

//----------------------------------------------------------------------
void SeedFromNuclearInteraction::setMeasurements(const TSOS& inner_TSOS, ConstRecHitPointer ihit, ConstRecHitPointer ohit) {

       // delete pointer to TrackingRecHits
       theHits.clear();

       // get the inner and outer transient TrackingRecHits
       innerHit_ = ihit;
       outerHit_ = ohit;

       //theHits.push_back(  inner_TM.recHit() ); // put temporarily - TODO: remove this line
       theHits.push_back(  outerHit_  );

       initialTSOS_.reset( new TrajectoryStateOnSurface(inner_TSOS) );

       // calculate the initial FreeTrajectoryState.
       freeTS_.reset(stateWithError());

       // check transverse momentum
       if(freeTS_->momentum().perp() < ptMin) { isValid_ = false; }
       else {
          // convert freeTS_ into a persistent TSOS on the outer surface
          isValid_ = construct(); }
}
//----------------------------------------------------------------------
void SeedFromNuclearInteraction::setMeasurements(TangentHelix& thePrimaryHelix, const TSOS& inner_TSOS, ConstRecHitPointer ihit, ConstRecHitPointer ohit) {

       // delete pointer to TrackingRecHits
       theHits.clear();

       // get the inner and outer transient TrackingRecHits
       innerHit_ = ihit;
       outerHit_ = ohit;

       GlobalPoint innerPos = theTrackerGeom->idToDet(innerHit_->geographicalId())->surface().toGlobal(innerHit_->localPosition());
       GlobalPoint outerPos = theTrackerGeom->idToDet(outerHit_->geographicalId())->surface().toGlobal(outerHit_->localPosition());

       TangentHelix helix(thePrimaryHelix, outerPos, innerPos);

       theHits.push_back( innerHit_ );
       theHits.push_back( outerHit_ );

       initialTSOS_.reset( new TrajectoryStateOnSurface(inner_TSOS) );

       // calculate the initial FreeTrajectoryState from the inner and outer TM assuming that the helix equation is already known.
       freeTS_.reset(stateWithError(helix));

       if(freeTS_->momentum().perp() < ptMin) { isValid_ = false; }
       else {
          // convert freeTS_ into a persistent TSOS on the outer surface
          isValid_ = construct(); }
}
//----------------------------------------------------------------------
FreeTrajectoryState* SeedFromNuclearInteraction::stateWithError() const {

   // Calculation of the helix assuming that the secondary track has the same direction
   // than the primary track and pass through the inner and outer hits.
   GlobalVector direction = initialTSOS_->globalDirection();
   GlobalPoint inner = initialTSOS_->globalPosition();
   TangentHelix helix(direction, inner, outerHitPosition());

   return stateWithError(helix);
}
//----------------------------------------------------------------------
FreeTrajectoryState* SeedFromNuclearInteraction::stateWithError(TangentHelix& helix) const {

//   typedef TkRotation<float> Rotation;

   GlobalVector dirAtVtx = helix.directionAtVertex();
   const MagneticField& mag = initialTSOS_->globalParameters().magneticField();

   // Get the global parameters of the trajectory
   // we assume that the magnetic field at the vertex is equal to the magnetic field at the inner TM.
   GlobalTrajectoryParameters gtp(helix.vertexPoint(), dirAtVtx , helix.charge(mag.inTesla(helix.vertexPoint()).z())/helix.rho(), 0, &mag);

   // Error matrix in a frame where z is in the direction of the track at the vertex
   AlgebraicSymMatrix66 primaryError( initialTSOS_->cartesianError().matrix() );
   double p_max = initialTSOS_->globalParameters().momentum().mag();
   AlgebraicMatrix33 rot = this->rotationMatrix( dirAtVtx );

   AlgebraicMatrix66 globalRotation;
   globalRotation.Place_at(rot,0,0);
   globalRotation.Place_at(rot,3,3);
   AlgebraicSymMatrix66 primaryErrorInNewFrame = ROOT::Math::Similarity(globalRotation, primaryError);

   AlgebraicSymMatrix66 secondaryErrorInNewFrame = AlgebraicMatrixID();
   double p_perp_max = 2; // energy max of a secondary track emited perpendicularly to the 
                          // primary track is +/- 2 GeV
   secondaryErrorInNewFrame(0,0) = primaryErrorInNewFrame(0,0)+helix.vertexError()*p_perp_max/p_max;
   secondaryErrorInNewFrame(1,1) = primaryErrorInNewFrame(1,1)+helix.vertexError()*p_perp_max/p_max;
   secondaryErrorInNewFrame(2,2) = helix.vertexError() * helix.vertexError();
   secondaryErrorInNewFrame(3,3) = p_perp_max*p_perp_max;  
   secondaryErrorInNewFrame(4,4) = p_perp_max*p_perp_max; 
   secondaryErrorInNewFrame(5,5) = p_max*p_max;

   AlgebraicSymMatrix66 secondaryError = ROOT::Math::SimilarityT(globalRotation, secondaryErrorInNewFrame);

   return new FreeTrajectoryState( gtp, CartesianTrajectoryError(secondaryError) );
}

//----------------------------------------------------------------------
bool SeedFromNuclearInteraction::construct() {

   // loop on all hits in theHits
   KFUpdator                 theUpdator;

   const TrackingRecHit* hit = 0;

   LogDebug("NuclearSeedGenerator") << "Seed ** initial state " << freeTS_->cartesianError().matrix();

   for ( unsigned int iHit = 0; iHit < theHits.size(); iHit++) {
     hit = theHits[iHit]->hit();
     TrajectoryStateOnSurface state = (iHit==0) ?
        thePropagator->propagate( *freeTS_, theTrackerGeom->idToDet(hit->geographicalId())->surface())
       : thePropagator->propagate( *updatedTSOS_, theTrackerGeom->idToDet(hit->geographicalId())->surface());

     if (!state.isValid()) return false;

     const TransientTrackingRecHit::ConstRecHitPointer& tth = theHits[iHit];
     updatedTSOS_.reset( new TrajectoryStateOnSurface(theUpdator.update(state, *tth)) );

   }

   TrajectoryStateTransform transformer;

   LogDebug("NuclearSeedGenerator") << "Seed ** updated state " << updatedTSOS_->cartesianError().matrix();

   pTraj = boost::shared_ptr<PTrajectoryStateOnDet>( transformer.persistentState(*updatedTSOS_, outerHitDetId().rawId()) );
   return true;
}

//----------------------------------------------------------------------
edm::OwnVector<TrackingRecHit>  SeedFromNuclearInteraction::hits() const {
    recHitContainer      _hits;
    for( ConstRecHitContainer::const_iterator it = theHits.begin(); it!=theHits.end(); it++ ){
           _hits.push_back( it->get()->hit()->clone() );
    }
    return _hits;
}
//----------------------------------------------------------------------
AlgebraicMatrix33 SeedFromNuclearInteraction::rotationMatrix(const GlobalVector& perp) const {

   AlgebraicMatrix33 result;

   // z axis coincides with perp
   GlobalVector zAxis = perp.unit();

   // x axis has no global Z component
   GlobalVector xAxis;
   if ( zAxis.x() != 0 || zAxis.y() != 0) {
     // precision is not an issue here, just protect against divizion by zero
     xAxis = GlobalVector( -zAxis.y(), zAxis.x(), 0).unit();
   }
   else { // perp coincides with global Z
     xAxis = GlobalVector( 1, 0, 0);
   }

   // y axis obtained by cross product
   GlobalVector yAxis( zAxis.cross( xAxis));

  result(0,0) = xAxis.x();
  result(0,1) = xAxis.y();
  result(0,2) = xAxis.z();
  result(1,0) = yAxis.x();
  result(1,1) = yAxis.y();
  result(1,2) = yAxis.z();
  result(2,0) = zAxis.x();
  result(2,1) = zAxis.y();
  result(2,2) = zAxis.z();
  return result;
}