MuonSeedFromRecHits.cc

Go to the documentation of this file.

#include "RecoMuon/TrackingTools/interface/MuonSeedFromRecHits.h"

#include "RecoMuon/TransientTrackingRecHit/interface/MuonTransientTrackingRecHit.h"

#include "RecoMuon/TrackingTools/interface/MuonPatternRecoDumper.h"

#include "MagneticField/Engine/interface/MagneticField.h"
#include "MagneticField/Records/interface/IdealMagneticFieldRecord.h"

#include "TrackingTools/TrajectoryState/interface/TrajectoryStateTransform.h"
#include "TrackingTools/DetLayers/interface/DetLayer.h"

#include "DataFormats/TrajectoryState/interface/PTrajectoryStateOnDet.h"
#include "DataFormats/Common/interface/OwnVector.h"
#include "FWCore/Framework/interface/EventSetup.h"
#include "FWCore/Framework/interface/ESHandle.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"

#include "gsl/gsl_statistics.h"

using namespace std;

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

MuonSeedFromRecHits::MuonSeedFromRecHits() : theField(nullptr) {}

TrajectorySeed MuonSeedFromRecHits::createSeed(float ptmean, float sptmean, ConstMuonRecHitPointer last) const {
  const std::string metname = "Muon|RecoMuon|MuonSeedFromRecHits";

  MuonPatternRecoDumper debug;

  // FIXME: put it into a parameter set!
  double theMinMomentum = 3.0;
  int charge = std::copysign(1, ptmean);

  // Minimal pt
  if (fabs(ptmean) < theMinMomentum)
    ptmean = theMinMomentum * charge;

  AlgebraicVector t(4);
  AlgebraicSymMatrix mat(5, 0);

  // Fill the LocalTrajectoryParameters
  LocalPoint segPos = last->localPosition();
  GlobalVector mom = last->globalPosition() - GlobalPoint();
  GlobalVector polar(GlobalVector::Spherical(mom.theta(), last->globalDirection().phi(), 1.));
  polar *= fabs(ptmean) / polar.perp();
  LocalVector segDirFromPos = last->det()->toLocal(polar);

  LocalTrajectoryParameters param(segPos, segDirFromPos, charge);

  // this perform H.T() * parErr * H, which is the projection of the
  // the measurement error (rechit rf) to the state error (TSOS rf)
  // Legenda:
  // H => is the 4x5 projection matrix
  // parError the 4x4 parameter error matrix of the RecHit

  // LogTrace(metname) << "Projection matrix:\n" << last->projectionMatrix();
  // LogTrace(metname) << "Error matrix:\n" << last->parametersError();

  mat = last->parametersError().similarityT(last->projectionMatrix());

  float p_err = sqr(sptmean / (ptmean * ptmean));
  mat[0][0] = p_err;

  LocalTrajectoryError error(asSMatrix<5>(mat));

  // Create the TrajectoryStateOnSurface
  TrajectoryStateOnSurface tsos(param, error, last->det()->surface(), theField);

  // The following LogTraces must be moved somewhere else (StandAloneTrajectoryBuilder)
  // Here the TSOS does not have the magnetic field set, so dumpTSOS causes a crash
  // (when LogTrace/LogDebug is activated)
  //LogTrace(metname) << "Trajectory State on Surface before the extrapolation"<<endl;
  //LogTrace(metname) << debug.dumpTSOS(tsos);

  // Take the DetLayer on which relies the rechit
  DetId id = last->geographicalId();
  // Segment layer
  //LogTrace(metname) << "The RecSegment relies on: "<<endl;
  //LogTrace(metname) << debug.dumpMuonId(id);
  //LogTrace(metname) << debug.dumpTSOS(tsos);

  // Transform it in a TrajectoryStateOnSurface

  PTrajectoryStateOnDet const& seedTSOS = trajectoryStateTransform::persistentState(tsos, id.rawId());

  edm::OwnVector<TrackingRecHit> container;
  for (unsigned l = 0; l < theRhits.size(); l++) {
    container.push_back(theRhits[l]->hit()->clone());
  }

  TrajectorySeed theSeed(seedTSOS, container, alongMomentum);

  return theSeed;
}