VertexDistanceXY.cc

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#include "RecoVertex/VertexTools/interface/VertexDistanceXY.h"
#include "DataFormats/GeometryVector/interface/GlobalVector.h"
#include "RecoVertex/VertexPrimitives/interface/VertexState.h"
#include "FWCore/Utilities/interface/Exception.h"
#include <cfloat>

using namespace reco;

Measurement1D VertexDistanceXY::signedDistance(const Vertex& vtx1,
                                               const Vertex& vtx2,
                                               const GlobalVector& momentum) const {
  Measurement1D unsignedDistance = distance(vtx1, vtx2);
  Basic3DVector<float> diff = Basic3DVector<float>(vtx2.position()) - Basic3DVector<float>(vtx1.position());
  if ((momentum.x() * diff.x() + momentum.y() * diff.y()) < 0)
    return Measurement1D(-1.0 * unsignedDistance.value(), unsignedDistance.error());
  return unsignedDistance;
}

Measurement1D VertexDistanceXY::distance(const GlobalPoint& vtx1Position,
                                         const GlobalError& vtx1PositionError,
                                         const GlobalPoint& vtx2Position,
                                         const GlobalError& vtx2PositionError) const {
  AlgebraicSymMatrix33 error = vtx1PositionError.matrix() + vtx2PositionError.matrix();
  GlobalVector diff = vtx1Position - vtx2Position;
  AlgebraicVector3 vDiff;
  vDiff[0] = diff.x();
  vDiff[1] = diff.y();
  vDiff[2] = 0.;

  double dist = sqrt(pow(diff.x(), 2) + pow(diff.y(), 2));

  double err2 = ROOT::Math::Similarity(error, vDiff);
  double err = 0;
  if (dist != 0)
    err = sqrt(err2) / dist;

  return Measurement1D(dist, err);
}

float VertexDistanceXY::compatibility(const GlobalPoint& vtx1Position,
                                      const GlobalError& vtx1PositionError,
                                      const GlobalPoint& vtx2Position,
                                      const GlobalError& vtx2PositionError) const {
  // error matrix of residuals
  AlgebraicSymMatrix33 err1 = vtx1PositionError.matrix();
  AlgebraicSymMatrix33 err2 = vtx2PositionError.matrix();
  AlgebraicSymMatrix22 error;
  error[0][0] = err1[0][0] + err2[0][0];
  error[0][1] = err1[0][1] + err2[0][1];
  error[1][1] = err1[1][1] + err2[1][1];
  if (error == theNullMatrix)
    return FLT_MAX;

  // position residuals
  GlobalVector diff = vtx2Position - vtx1Position;
  AlgebraicVector2 vDiff;
  vDiff[0] = diff.x();
  vDiff[1] = diff.y();

  // Invert error matrix of residuals
  bool ifail = !error.Invert();
  if (ifail) {
    throw cms::Exception("VertexDistanceXY::matrix inversion problem");
  }

  return ROOT::Math::Similarity(error, vDiff);
}