/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_5/src/RecoBTag/SecondaryVertex/src/SecondaryVertex.cc

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#include <cmath>

#include <Math/Functions.h>
#include <Math/SVector.h>
#include <Math/SMatrix.h>

#include "DataFormats/GeometryCommonDetAlgo/interface/Measurement1D.h"
#include "DataFormats/GeometryVector/interface/GlobalVector.h"
#include "DataFormats/VertexReco/interface/Vertex.h"

#include "RecoBTag/SecondaryVertex/interface/SecondaryVertex.h"

using namespace reco;

Measurement1D
SecondaryVertex::computeDist2d(const Vertex &pv, const Vertex &sv,
                               const GlobalVector &direction, bool withPVError)
{
        typedef ROOT::Math::SVector<double, 2> SVector2;
        typedef ROOT::Math::SMatrix<double, 2, 2,
                        ROOT::Math::MatRepSym<double, 2> > SMatrixSym2;

        SMatrixSym2 cov = sv.covariance().Sub<SMatrixSym2>(0, 0);
        if (withPVError)
                cov += pv.covariance().Sub<SMatrixSym2>(0, 0);

        SVector2 vector(sv.position().X() - pv.position().X(),
                        sv.position().Y() - pv.position().Y());

        double dist = ROOT::Math::Mag(vector);
        double error = ROOT::Math::Similarity(cov, vector);
        if (error > 0.0 && dist > 1.0e-9)
                error = std::sqrt(error) / dist;
        else
                error = -1.0;

        if ((vector[0] * direction.x() +
             vector[1] * direction.y()) < 0.0)
                dist = -dist;

        return Measurement1D(dist, error);
}

Measurement1D
SecondaryVertex::computeDist3d(const Vertex &pv, const Vertex &sv,
                               const GlobalVector &direction, bool withPVError)
{
        typedef ROOT::Math::SVector<double, 3> SVector3;
        typedef ROOT::Math::SMatrix<double, 3, 3,
                        ROOT::Math::MatRepSym<double, 3> > SMatrixSym3;

        SMatrixSym3 cov = sv.covariance();
        if (withPVError)
                cov += pv.covariance();

        SVector3 vector(sv.position().X() - pv.position().X(),
                        sv.position().Y() - pv.position().Y(),
                        sv.position().Z() - pv.position().Z());

        double dist = ROOT::Math::Mag(vector);
        double error = ROOT::Math::Similarity(cov, vector);
        if (error > 0.0 && dist > 1.0e-9)
                error = std::sqrt(error) / dist;
        else
                error = -1.0;

        if ((vector[0] * direction.x() +
             vector[1] * direction.y() +
             vector[2] * direction.z()) < 0.0)
                dist = -dist;

        return Measurement1D(dist, error);
}