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PVPositionBuilder.cc

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#include "RecoPixelVertexing/PixelVertexFinding/interface/PVPositionBuilder.h"
#include <cmath>

PVPositionBuilder::PVPositionBuilder() {}

Measurement1D PVPositionBuilder::average(const reco::TrackRefVector &trks) const {
  // Cut and paste (more or less) from same class in ORCA framework
  double ntracks = double(trks.size());
  if (ntracks==0) return Measurement1D ( 0. , 0. );
  double sumZIP = 0;
  double err = 0;
  for (unsigned int i=0; i<trks.size(); i++) {
    sumZIP += trks[i]->dz(); // Z at IP
    err += trks[i]->dzError(); // error on Z at IP (I hope). Fix d.k.
  }  
  return Measurement1D ( sumZIP/ntracks, err/ntracks/std::sqrt(ntracks) );

}

Measurement1D PVPositionBuilder::wtAverage(const reco::TrackRefVector &trks) const {
  double ntracks = double(trks.size());
  if (ntracks==0) return Measurement1D ( 0.0 , 0.0 );
  double sumUp = 0;
  double sumDown = 0;
  double err = 0;
  for (unsigned int i=0; i<trks.size(); i++) {
    //    double err2 = trks[i]->covariance(3,3); // error on Z at IP (I hope)
    double err2 = trks[i]->dzError(); // Fix d.k.
    err2 *= err2;
    if (err2 != 0){
      sumUp += trks[i]->dz() * 1/err2; // error-weighted average of Z at IP
      sumDown += 1/err2;
    }
    err += std::sqrt( err2 );
  }  
  if (sumDown > 0) return Measurement1D ( sumUp/sumDown , err/ntracks/sqrt(ntracks) );
  else return Measurement1D ( 0.0 , 0.0 );
}  

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