Class Acts::LinearizedTrack

class LinearizedTrack

Class for linear expansion of track parameters in vicinity of vertex.

The measurement equation is linearized in the following way:

F_k= D_k (x_k - x_0k) + E_k (p_k - p_0k) + F^0_k

where F_k are the parameters at perigee nearest to the linearization point, x_k is the position of the vertex, p_k the track momentum at the vertex, and F^0_k is the constant term of expansion. D_k and E_k are matrices of derivatives, denoted hereafter as “positionJacobian” and “momentumJacobian” respectively.

Public Functions

LinearizedTrack() = default
inline LinearizedTrack(const BoundVector &paramsAtPCA, const BoundSymMatrix &parCovarianceAtPCA, const BoundSymMatrix &parWeightAtPCA, const Vector4 &linPoint, const ActsMatrix<eBoundSize, 4> &posJacobian, const ActsMatrix<eBoundSize, 3> &momJacobian, const Vector4 &position, const Vector3 &momentum, const BoundVector &constTerm)

Constructor taking perigee parameters and covariance matrix of track propagated to closest approach (PCA) of linearization point, position and momentum Jacobian and const term.

  • paramsAtPCA – Parameters at point of closest approach

  • parCovarianceAtPCA – Parameter covariance matrix at point of closest approach

  • parWeightAtPCA – The weight at the point of closest approach

  • linPoint – Linearization point

  • posJacobian – Position jacobian

  • momJacobian – Momentum jacobian

  • position – Position at point of closest approach

  • momentum – Momentum at point of closest approach

  • constTerm – Constant term in taylor expansion

Public Members

BoundVector constantTerm = {BoundVector::Zero()}
BoundSymMatrix covarianceAtPCA = {BoundSymMatrix::Zero()}
Vector4 linearizationPoint = {Vector4::Zero()}
Vector3 momentumAtPCA = {Vector3::Zero()}
ActsMatrix<eBoundSize, 3> momentumJacobian = {ActsMatrix<eBoundSize, 3>::Zero()}
BoundVector parametersAtPCA = {BoundVector::Zero()}
Vector4 positionAtPCA = {Vector4::Zero()}
ActsMatrix<eBoundSize, 4> positionJacobian = {ActsMatrix<eBoundSize, 4>::Zero()}
BoundSymMatrix weightAtPCA = {BoundSymMatrix::Zero()}