Template Class HelicalTrackLinearizer

Nested Relationships

Nested Types

Class Documentation

template<typename propagator_t, typename propagator_options_t = PropagatorOptions<>>
class Acts::HelicalTrackLinearizer

Linearizes the measurement equation (dependance of track parameters on the vertex position and track momentum at vertex) at the vicinity of the user-provided linearization point.

The measurement equation is linearized in the following way:

q_k= A_k (x_k - x_0k) + B_k (p_k - p_0k) + c_k

where q_k are the parameters at perigee nearest to the lin point, x_k is the position of the vertex, p_k the track momentum at the vertex, and c_k is the constant term of expansion. A_k and B_k are matrices of derivatives, denoted hereafter as “positionJacobian” and “momentumJacobian” respectively.

Ref.(1) - CERN-THESIS-2010-027, Giacinto Piacquadio (Freiburg U.)

Template Parameters
  • propagator_t: Propagator type

  • propagator_options_t: Propagator options type

Public Types

using Propagator_t = propagator_t

Public Functions

HelicalTrackLinearizer(const Config &config)

Constructor.

Parameters
  • config: Configuration object

Result<LinearizedTrack> linearizeTrack(const BoundTrackParameters &params, const Vector4 &linPoint, const Acts::GeometryContext &gctx, const Acts::MagneticFieldContext &mctx, State &state) const

Function that linearizes BoundTrackParameters at given linearization point.

Return

Linearized track

Parameters
  • params: Parameters to linearize

  • linPoint: Linearization point

  • gctx: The geometry context

  • mctx: The magnetic field context

  • state: The state object

struct Config

Configuration struct.

Public Functions

Config(std::shared_ptr<MagneticFieldProvider> bIn, std::shared_ptr<Propagator_t> prop)

@ Config constructor if magnetic field is present

Parameters
  • bIn: The magnetic field

  • prop: The propagator

Config(std::shared_ptr<Propagator_t> prop)

Config constructor without B field -> uses NullBField.

Parameters
  • prop: The propagator

Public Members

std::shared_ptr<MagneticFieldProvider> bField
double maxRho = 1e+15
double minQoP = 1e-15
std::shared_ptr<Propagator_t> propagator
struct State

Public Functions

State(MagneticFieldProvider::Cache fieldCacheIn)

The state constructor.

Parameters
  • mctx: The magnetic field context

Public Members

MagneticFieldProvider::Cache fieldCache

Magnetic field cache.