Estimator for impact point calculations A description of the underlying mathematics can be found here: https://github.com/acts-project/acts/pull/2506 TODO: Upload reference at a better place. More...

#include <acts/blob/sPHENIX/Core/include/Acts/Vertexing/ImpactPointEstimator.hpp>

Collaboration diagram for Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >:

Classes
struct	Config

struct	State
	State struct. More...

Public Member Functions
	ImpactPointEstimator (const Config &cfg)
	Constructor.

Result< double >	calculateDistance (const GeometryContext &gctx, const BoundTrackParameters &trkParams, const Vector3 &vtxPos, State &state) const
	Calculates 3D distance between a track and a vertex.

Result< BoundTrackParameters >	estimate3DImpactParameters (const GeometryContext &gctx, const Acts::MagneticFieldContext &mctx, const BoundTrackParameters &trkParams, const Vector3 &vtxPos, State &state) const
	Estimates the track parameters at the 3D PCA (i.e., a point of minimal 3D distance) to a vertex. The track parameters are defined wrt a reference plane that has its origin at the vertex position and whose z-axis points in the direction of the track momentum. The plane's x-axis points approximately from the vertex to the 3D PCA (it is only approximate because we force it to be orthogonal to the z-axis). The y-axis is calculated as a cross product between x- and z-axis.

template<unsigned int nDim>
Result< double >	getVertexCompatibility (const GeometryContext &gctx, const BoundTrackParameters *trkParams, const ActsVector< nDim > &vertexPos) const
	Estimates the compatibility of a track to a vertex based on their 3D (if nDim = 3) or 4D (if nDim = 4) distance and the track covariance.

template<unsigned int nDim>
Result< std::pair < Acts::ActsVector< nDim > , Acts::Vector3 > >	getDistanceAndMomentum (const GeometryContext &gctx, const BoundTrackParameters &trkParams, const ActsVector< nDim > &vtxPos, State &state) const
	Calculate the distance between a track and a vertex by finding the corresponding 3D PCA. Returns also the momentum direction at the 3D PCA. The template parameter nDim determines whether we calculate the 3D distance (nDim = 3) or the 4D distance (nDim = 4) to the 3D PCA.

Result< ImpactParametersAndSigma >	getImpactParameters (const BoundTrackParameters &track, const Vertex< input_track_t > &vtx, const GeometryContext &gctx, const MagneticFieldContext &mctx, bool calculateTimeIP=false) const
	Calculates the impact parameters of a track w.r.t. a vertex. The corresponding errors are approximated by summing the variances of the track and the vertex.

Result< std::pair< double, double > >	getLifetimeSignOfTrack (const BoundTrackParameters &track, const Vertex< input_track_t > &vtx, const Acts::Vector3 &direction, const GeometryContext &gctx, const MagneticFieldContext &mctx) const
	Estimates the sign of the 2D and Z lifetime of a given track w.r.t. a vertex and a direction (e.g. a jet direction) by propagating the trajectory state towards the vertex position and computing the scalar product with the direction vector.

Result< double >	get3DLifetimeSignOfTrack (const BoundTrackParameters &track, const Vertex< input_track_t > &vtx, const Acts::Vector3 &direction, const GeometryContext &gctx, const MagneticFieldContext &mctx) const
	Estimates the sign of the 3D lifetime of a given track w.r.t. a vertex and a direction (e.g. a jet direction)

Private Member Functions
Result< double >	performNewtonOptimization (const Vector3 &helixCenter, const Vector3 &vtxPos, double phi, double theta, double rho) const
	Performs a Newton approximation to retrieve a point of closest approach in 3D to a reference position.

Private Attributes
const Config	m_cfg
	Configuration object.

Detailed Description

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

Estimator for impact point calculations A description of the underlying mathematics can be found here: https://github.com/acts-project/acts/pull/2506 TODO: Upload reference at a better place.

Definition at line 47 of file ImpactPointEstimator.hpp.

View newest version in sPHENIX GitHub at line 47 of file ImpactPointEstimator.hpp

Constructor & Destructor Documentation

template<typename input_track_t, typename propagator_t, typename propagator_options_t = PropagatorOptions<>>

Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::ImpactPointEstimator ( const Config & cfg )

inline

Constructor.

Parameters

cfg	Configuration object

Definition at line 89 of file ImpactPointEstimator.hpp.

View newest version in sPHENIX GitHub at line 89 of file ImpactPointEstimator.hpp

Member Function Documentation

template<typename input_track_t , typename propagator_t , typename propagator_options_t >

Acts::Result< double > Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::calculateDistance	(	const GeometryContext &	gctx,
		const BoundTrackParameters &	trkParams,
		const Vector3 &	vtxPos,
		State &	state
	)		const

Calculates 3D distance between a track and a vertex.

Parameters

gctx	The geometry context
trkParams	Track parameters
vtxPos	3D position to calculate the distance to
state	The state object

Returns: Distance

Definition at line 18 of file ImpactPointEstimator.ipp.

View newest version in sPHENIX GitHub at line 18 of file ImpactPointEstimator.ipp

References gctx, and filter::state.

template<typename input_track_t , typename propagator_t , typename propagator_options_t >

Acts::Result< Acts::BoundTrackParameters > Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::estimate3DImpactParameters	(	const GeometryContext &	gctx,
		const Acts::MagneticFieldContext &	mctx,
		const BoundTrackParameters &	trkParams,
		const Vector3 &	vtxPos,
		State &	state
	)		const

Estimates the track parameters at the 3D PCA (i.e., a point of minimal 3D distance) to a vertex. The track parameters are defined wrt a reference plane that has its origin at the vertex position and whose z-axis points in the direction of the track momentum. The plane's x-axis points approximately from the vertex to the 3D PCA (it is only approximate because we force it to be orthogonal to the z-axis). The y-axis is calculated as a cross product between x- and z-axis.

Parameters

gctx	The geometry context
mctx	The magnetic field context
trkParams	Track parameters
vtxPos	Reference position (vertex)
state	The state object

Returns: Track parameters at the 3D PCA

Definition at line 35 of file ImpactPointEstimator.ipp.

View newest version in sPHENIX GitHub at line 35 of file ImpactPointEstimator.ipp

References closest(), physmon_track_finding_ttbar::deltaR, gctx, m_cfg(), and filter::state.

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template<typename input_track_t, typename propagator_t , typename propagator_options_t >

Acts::Result< double > Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::get3DLifetimeSignOfTrack	(	const BoundTrackParameters &	track,
		const Vertex< input_track_t > &	vtx,
		const Acts::Vector3 &	direction,
		const GeometryContext &	gctx,
		const MagneticFieldContext &	mctx
	)		const

Estimates the sign of the 3D lifetime of a given track w.r.t. a vertex and a direction (e.g. a jet direction)

Parameters

track	Track to estimate the IP from
vtx	Vertex the track belongs to
direction	The direction
gctx	The geometry context
mctx	The magnetic field context

Returns: The value of the 3D lifetime

Definition at line 497 of file ImpactPointEstimator.ipp.

View newest version in sPHENIX GitHub at line 497 of file ImpactPointEstimator.ipp

References m_cfg(), Acts::Vertex< input_track_t >::position(), and sign().

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template<typename input_track_t , typename propagator_t , typename propagator_options_t >

template<unsigned int nDim>

Acts::Result< std::pair< Acts::ActsVector< nDim >, Acts::Vector3 > > Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::getDistanceAndMomentum	(	const GeometryContext &	gctx,
		const BoundTrackParameters &	trkParams,
		const ActsVector< nDim > &	vtxPos,
		State &	state
	)		const

Calculate the distance between a track and a vertex by finding the corresponding 3D PCA. Returns also the momentum direction at the 3D PCA. The template parameter nDim determines whether we calculate the 3D distance (nDim = 3) or the 4D distance (nDim = 4) to the 3D PCA.

Note: For straight tracks we use an analytical solution; for helical tracks we use the Newton method.

Template Parameters

nDim	Number of dimensions used to compute compatibility

Note: If nDim = 3 we only consider spatial dimensions; if nDim = 4, we also consider time. Other values are not allowed.

Parameters

gctx	Geometry context
trkParams	Track parameters
vtxPos	Vertex position
state	The state object

Definition at line 235 of file ImpactPointEstimator.ipp.

View newest version in sPHENIX GitHub at line 235 of file ImpactPointEstimator.ipp

References Acts::Surface::center(), physmon_track_finding_ttbar::deltaR, Acts::GenericBoundTrackParameters< particle_hypothesis_t >::direction(), Acts::eBoundLoc0, Acts::eBoundLoc1, Acts::eBoundPhi, Acts::eBoundQOverP, Acts::eBoundTheta, Acts::eBoundTime, eZ, Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::State::fieldCache, m_cfg(), merge_hashes::p, Acts::GenericBoundTrackParameters< particle_hypothesis_t >::parameters(), Acts::GenericBoundTrackParameters< particle_hypothesis_t >::particleHypothesis(), ActsTests::PropagationDatasets::phi, Acts::GenericBoundTrackParameters< particle_hypothesis_t >::position(), Acts::GenericBoundTrackParameters< particle_hypothesis_t >::referenceSurface(), rho, and ActsTests::PropagationDatasets::theta.

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template<typename input_track_t, typename propagator_t , typename propagator_options_t >

Acts::Result< Acts::ImpactParametersAndSigma > Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::getImpactParameters	(	const BoundTrackParameters &	track,
		const Vertex< input_track_t > &	vtx,
		const GeometryContext &	gctx,
		const MagneticFieldContext &	mctx,
		bool	calculateTimeIP = `false`
	)		const

Calculates the impact parameters of a track w.r.t. a vertex. The corresponding errors are approximated by summing the variances of the track and the vertex.

Parameters

track	Track whose impact parameters are calculated
vtx	Vertex corresponding to the track
gctx	The geometry context
mctx	The magnetic field context
calculateTimeIP	If true, the difference in time is computed

Definition at line 370 of file ImpactPointEstimator.ipp.

View newest version in sPHENIX GitHub at line 370 of file ImpactPointEstimator.ipp

References closest(), Acts::Vertex< input_track_t >::covariance(), Acts::ImpactParametersAndSigma::d0, Acts::ImpactParametersAndSigma::deltaT, Acts::GenericBoundTrackParameters< particle_hypothesis_t >::direction(), Acts::eTime, Acts::eX, Acts::eY, eZ, Acts::Vertex< input_track_t >::fullCovariance(), m_cfg(), Acts::Vertex< input_track_t >::position(), Acts::GenericBoundTrackParameters< particle_hypothesis_t >::position(), Acts::ImpactParametersAndSigma::sigmaD0, Acts::ImpactParametersAndSigma::sigmaDeltaT, Acts::ImpactParametersAndSigma::sigmaZ0, Acts::Vertex< input_track_t >::time(), and Acts::ImpactParametersAndSigma::z0.

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template<typename input_track_t, typename propagator_t , typename propagator_options_t >

Acts::Result< std::pair< double, double > > Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::getLifetimeSignOfTrack	(	const BoundTrackParameters &	track,
		const Vertex< input_track_t > &	vtx,
		const Acts::Vector3 &	direction,
		const GeometryContext &	gctx,
		const MagneticFieldContext &	mctx
	)		const

Estimates the sign of the 2D and Z lifetime of a given track w.r.t. a vertex and a direction (e.g. a jet direction) by propagating the trajectory state towards the vertex position and computing the scalar product with the direction vector.

Parameters

track	Track to estimate the IP from
vtx	Vertex the track belongs to
direction	The direction
gctx	The geometry context
mctx	The magnetic field context

Returns: A pair holding the sign for the 2D and Z lifetimes

Definition at line 453 of file ImpactPointEstimator.ipp.

View newest version in sPHENIX GitHub at line 453 of file ImpactPointEstimator.ipp

References Acts::eBoundLoc0, Acts::eBoundLoc1, Acts::eBoundPhi, Acts::eBoundTheta, eta, m_cfg(), ActsTests::PropagationDatasets::phi, Acts::Vertex< input_track_t >::position(), and ActsTests::PropagationDatasets::theta.

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template<typename input_track_t , typename propagator_t , typename propagator_options_t >

template<unsigned int nDim>

Acts::Result< double > Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::getVertexCompatibility	(	const GeometryContext &	gctx,
		const BoundTrackParameters *	trkParams,
		const ActsVector< nDim > &	vertexPos
	)		const

Estimates the compatibility of a track to a vertex based on their 3D (if nDim = 3) or 4D (if nDim = 4) distance and the track covariance.

Note: Confusingly, a smaller compatibility means that a track is more compatible.

Template Parameters

nDim	Number of dimensions used to compute compatibility

Note: If nDim = 3 we only consider spatial dimensions; if nDim = 4, we also consider time. Other values are not allowed.

Parameters

gctx	The Geometry context
trkParams	Track parameters at point of closest approach in 3D as retrieved by estimate3DImpactParameters
vertexPos	The vertex position

Returns: The compatibility value

Definition at line 109 of file ImpactPointEstimator.ipp.

View newest version in sPHENIX GitHub at line 109 of file ImpactPointEstimator.ipp

References Acts::GenericBoundTrackParameters< particle_hypothesis_t >::covariance(), Acts::eBoundTime, Acts::eX, Acts::eY, Acts::GenericBoundTrackParameters< particle_hypothesis_t >::impactParameterCovariance(), Acts::GenericBoundTrackParameters< particle_hypothesis_t >::parameters(), Acts::GenericBoundTrackParameters< particle_hypothesis_t >::referenceSurface(), Acts::GenericBoundTrackParameters< particle_hypothesis_t >::spatialImpactParameterCovariance(), and Acts::Surface::transform().

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template<typename input_track_t , typename propagator_t , typename propagator_options_t >

Acts::Result< double > Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::performNewtonOptimization	(	const Vector3 &	helixCenter,
		const Vector3 &	vtxPos,
		double	phi,
		double	theta,
		double	rho
	)		const

private

Performs a Newton approximation to retrieve a point of closest approach in 3D to a reference position.

Parameters

helixCenter	Position of the helix center
vtxPos	Vertex position
phi	Azimuthal momentum angle

Note: Modifying phi corresponds to moving along the track. This function optimizes phi until we reach a 3D PCA.

Parameters

theta	Polar momentum angle (constant along the track)
rho	Signed helix radius

Returns: Phi value at 3D PCA

Definition at line 178 of file ImpactPointEstimator.ipp.

View newest version in sPHENIX GitHub at line 178 of file ImpactPointEstimator.ipp

References deltaPhi(), m_cfg(), nIter, and ActsTests::PropagationDatasets::phi.

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Member Data Documentation

template<typename input_track_t, typename propagator_t, typename propagator_options_t = PropagatorOptions<>>

const Config Acts::ImpactPointEstimator< input_track_t, propagator_t, propagator_options_t >::m_cfg

private

Configuration object.

Definition at line 210 of file ImpactPointEstimator.hpp.

View newest version in sPHENIX GitHub at line 210 of file ImpactPointEstimator.hpp

The documentation for this class was generated from the following files:

acts/blob/sPHENIX/Core/include/Acts/Vertexing/ImpactPointEstimator.hpp
acts/blob/sPHENIX/Core/include/Acts/Vertexing/ImpactPointEstimator.ipp

Classes

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

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

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation

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