Algorithm for fitting tracks through a single RP. More...

#include <TotemRPLocalTrackFitterAlgorithm.h>

Classes
struct	RPDetCoordinateAlgebraObjs

Public Member Functions
bool	fitTrack (const edm::DetSetVector< TotemRPRecHit > &hits, double z_0, const TotemRPGeometry &tot_geom, TotemRPLocalTrack &fitted_track)
	performs the track fit, returns true if successful More...

void	reset ()
	Resets the reconstruction-data cache. More...

	TotemRPLocalTrackFitterAlgorithm (const edm::ParameterSet &conf)

Private Member Functions
RPDetCoordinateAlgebraObjs *	getDetAlgebraData (unsigned int det_id, const TotemRPGeometry &tot_rp_geom)

void	multiplyByDiagonalInPlace (TMatrixD &mt, const TVectorD &diag)
	A matrix multiplication shorthand. More...

RPDetCoordinateAlgebraObjs	prepareReconstAlgebraData (unsigned int det_id, const TotemRPGeometry &tot_rp_geom)
	Build the reconstruction data. More...

Static Private Member Functions
static TVector3	convert3vector (const CLHEP::Hep3Vector &v)

Private Attributes
std::unordered_map< unsigned int, RPDetCoordinateAlgebraObjs >	det_data_map_
	A cache of reconstruction data. Must be reset every time the geometry chagnges. More...

RPTopology	rp_topology_

Detailed Description

Algorithm for fitting tracks through a single RP.

Definition at line 32 of file TotemRPLocalTrackFitterAlgorithm.h.

Constructor & Destructor Documentation

TotemRPLocalTrackFitterAlgorithm::TotemRPLocalTrackFitterAlgorithm ( const edm::ParameterSet & conf )

Definition at line 23 of file TotemRPLocalTrackFitterAlgorithm.cc.

24 {

25 }

Member Function Documentation

static TVector3 TotemRPLocalTrackFitterAlgorithm::convert3vector ( const CLHEP::Hep3Vector & v )

inlinestaticprivate

Definition at line 67 of file TotemRPLocalTrackFitterAlgorithm.h.

     {
       return TVector3(v.x(),v.y(),v.z()) ;
     }

bool TotemRPLocalTrackFitterAlgorithm::fitTrack	(	const edm::DetSetVector< TotemRPRecHit > &	hits,
		double	z_0,
		const TotemRPGeometry &	tot_geom,
		TotemRPLocalTrack &	fitted_track
	)

performs the track fit, returns true if successful

Definition at line 79 of file TotemRPLocalTrackFitterAlgorithm.cc.

Referenced by TotemRPLocalTrackFitter::produce().

 {
   fitted_track.setValid(false);
 
   // bind hits with their algebra objects
   struct HitWithAlg
   {
     unsigned int detId;
     const TotemRPRecHit *hit;
     RPDetCoordinateAlgebraObjs *alg;
   };
   
   vector<HitWithAlg> applicable_hits;
 
   for (auto &ds : hits)
   {
     unsigned int detId = ds.detId();
 
     for (auto &h : ds)
     {
       RPDetCoordinateAlgebraObjs * alg = getDetAlgebraData(detId, tot_geom);
       if (alg->available_)
         applicable_hits.push_back({ detId, &h, alg});
     }
   }
   
   if (applicable_hits.size() < 5)
     return false;
   
   TMatrixD H(applicable_hits.size(), 4);
   TVectorD V(applicable_hits.size());
   TVectorD V_inv(applicable_hits.size());
   TVectorD U(applicable_hits.size());
   
   for(unsigned int i = 0;  i < applicable_hits.size(); ++i)
   {
     RPDetCoordinateAlgebraObjs *alg_obj = applicable_hits[i].alg;
 
     H(i,0) = alg_obj->readout_direction_.X();
     H(i,1) = alg_obj->readout_direction_.Y();
     double delta_z = alg_obj->centre_of_det_global_position_.Z()-z_0;
     H(i,2) = alg_obj->readout_direction_.X()*delta_z;
     H(i,3) = alg_obj->readout_direction_.Y()*delta_z;
     double var = applicable_hits[i].hit->getSigma();
     var*=var;
     V[i] = var;
     V_inv[i] = 1.0/var;
     U[i] = applicable_hits[i].hit->getPosition() - alg_obj->rec_u_0_;
   }
 
   TMatrixD H_T_V_inv(TMatrixD::kTransposed, H);
   multiplyByDiagonalInPlace(H_T_V_inv, V_inv);
   TMatrixD V_a(H_T_V_inv);
   TMatrixD V_a_mult(V_a, TMatrixD::kMult, H);
   try
   {
     V_a_mult.Invert();
   }
   catch (cms::Exception &e)
   {
     LogError("TotemRPLocalTrackFitterAlgorithm") << "Error in TotemRPLocalTrackFitterAlgorithm::fitTrack > "
       << "Fit matrix is singular. Skipping.";
     return false;
   }
 
   TMatrixD u_to_a(V_a_mult, TMatrixD::kMult, H_T_V_inv);
   TVectorD a(U);
   a *= u_to_a;
   
   fitted_track.setZ0(z_0);
   fitted_track.setParameterVector(a);
   fitted_track.setCovarianceMatrix(V_a_mult);
   
   double Chi_2 = 0;
   for(unsigned int i=0; i<applicable_hits.size(); ++i)
   {
     RPDetCoordinateAlgebraObjs *alg_obj = applicable_hits[i].alg;
     TVector2 readout_dir = alg_obj->readout_direction_;
     double det_z = alg_obj->centre_of_det_global_position_.Z();
     double sigma_str = applicable_hits[i].hit->getSigma();
     double sigma_str_2 = sigma_str*sigma_str;
     TVector2 fited_det_xy_point = fitted_track.getTrackPoint(det_z);
     double U_readout = applicable_hits[i].hit->getPosition() - alg_obj->rec_u_0_;
     double U_fited = (readout_dir*=fited_det_xy_point);
     double residual = U_fited - U_readout;
     TMatrixD V_T_Cov_X_Y(1,2);
     V_T_Cov_X_Y(0,0) = readout_dir.X();
     V_T_Cov_X_Y(0,1) = readout_dir.Y();
     TMatrixD V_T_Cov_X_Y_mult(V_T_Cov_X_Y, TMatrixD::kMult, fitted_track.trackPointInterpolationCovariance(det_z));
     double fit_strip_var = V_T_Cov_X_Y_mult(0,0)*readout_dir.X() + V_T_Cov_X_Y_mult(0,1)*readout_dir.Y();
     double pull_normalization = sqrt(sigma_str_2 - fit_strip_var);
     double pull = residual/pull_normalization;
     
     Chi_2 += residual*residual / sigma_str_2;
 
     TotemRPLocalTrack::FittedRecHit hit_point(*(applicable_hits[i].hit), TVector3(fited_det_xy_point.X(),
       fited_det_xy_point.Y(), det_z), residual, pull);
     fitted_track.addHit(applicable_hits[i].detId, hit_point);
   }
   
   fitted_track.setChiSquared(Chi_2);
   fitted_track.setValid(true);
   return true;
 }

TotemRPLocalTrackFitterAlgorithm::RPDetCoordinateAlgebraObjs * TotemRPLocalTrackFitterAlgorithm::getDetAlgebraData	(	unsigned int	det_id,
		const TotemRPGeometry &	tot_rp_geom
	)

private

Returns the reconstruction data for the chosen detector from the cache DetReconstructionDataMap. If it is not yet in the cache, calls PrepareReconstAlgebraData to make it.

Definition at line 65 of file TotemRPLocalTrackFitterAlgorithm.cc.

 {
   auto it = det_data_map_.find(det_id);
   if (it != det_data_map_.end())
   {
     return &(it->second);
   } else {
     det_data_map_[det_id] = prepareReconstAlgebraData(det_id, tot_rp_geom);
     return &det_data_map_[det_id];
   }
 }

void TotemRPLocalTrackFitterAlgorithm::multiplyByDiagonalInPlace	(	TMatrixD &	mt,
		const TVectorD &	diag
	)

private

A matrix multiplication shorthand.

Definition at line 187 of file TotemRPLocalTrackFitterAlgorithm.cc.

References i, and j.

 {
   for(int i=0; i<mt.GetNrows(); ++i)
   {
     for(int j=0; j<mt.GetNcols(); ++j)
     {
       mt[i][j] *= diag[j];
     }
   }
 }

TotemRPLocalTrackFitterAlgorithm::RPDetCoordinateAlgebraObjs TotemRPLocalTrackFitterAlgorithm::prepareReconstAlgebraData	(	unsigned int	det_id,
		const TotemRPGeometry &	tot_rp_geom
	)

private

Build the reconstruction data.

Definition at line 38 of file TotemRPLocalTrackFitterAlgorithm.cc.

References TotemRPLocalTrackFitterAlgorithm::RPDetCoordinateAlgebraObjs::available_, TotemRPLocalTrackFitterAlgorithm::RPDetCoordinateAlgebraObjs::centre_of_det_global_position_, TotemRPGeometry::GetDetTranslation(), TotemRPGeometry::LocalToGlobalDirection(), TotemRPLocalTrackFitterAlgorithm::RPDetCoordinateAlgebraObjs::readout_direction_, TotemRPLocalTrackFitterAlgorithm::RPDetCoordinateAlgebraObjs::rec_u_0_, and findQualityFiles::v.

 {
   RPDetCoordinateAlgebraObjs det_algebra_obj;
 
   det_algebra_obj.centre_of_det_global_position_ = convert3vector(tot_rp_geom.GetDetTranslation(det_id));
  
   HepMC::ThreeVector rp_topology_stripaxis = rp_topology_.GetStripReadoutAxisDir();
   CLHEP::Hep3Vector rp_topology_stripaxis_clhep;
   
   rp_topology_stripaxis_clhep.setX(rp_topology_stripaxis.x());
   rp_topology_stripaxis_clhep.setY(rp_topology_stripaxis.y());
   rp_topology_stripaxis_clhep.setZ(rp_topology_stripaxis.z());
  
   TVector3 rd_dir = convert3vector( tot_rp_geom.LocalToGlobalDirection(det_id, rp_topology_stripaxis_clhep ) );
   
   TVector2 v(rd_dir.X(), rd_dir.Y());
   det_algebra_obj.readout_direction_ = v.Unit();
   det_algebra_obj.rec_u_0_ = 0.0;
   det_algebra_obj.available_ = true;
   det_algebra_obj.rec_u_0_ = - (det_algebra_obj.readout_direction_ * det_algebra_obj.centre_of_det_global_position_.XYvector());
   
   return det_algebra_obj;
 }