double getChi2(const reco::TrackBase::ParameterVector &rParameters, const reco::TrackBase::CovarianceMatrix &recoTrackCovMatrix, const Basic3DVector< double > &momAtVtx, const Basic3DVector< double > &vert, int charge, const MagneticField &magfield, const reco::BeamSpot &bs)
basic method where chi2 is computed