Acts::AccumulatedMaterialSlab Class Reference

Accumulate material properties from multiple hits/track and multiple tracks. More...

#include <Acts/Material/AccumulatedMaterialSlab.hpp>

Public Member Functions
void	accumulate (MaterialSlab slabAlongTrack, double pathCorrection=1.)
	Add the material to the current per-track store.
std::pair< MaterialSlab, unsigned int >	totalAverage () const
	Return the average material properties from all accumulated tracks.
std::pair< float, unsigned int >	totalVariance () const
	Return the material variance from all accumulated tracks.
void	trackAverage (bool useEmptyTrack=false)
	Add the accumulated material for the current track to the total average.
void	trackVariance (MaterialSlab slabReference, bool useEmptyTrack=false)
	Use the accumulated material to update the material variance.

Detailed Description

Accumulate material properties from multiple hits/track and multiple tracks.

This is a helper class for the SurfaceMaterialMapper to handle material accumulation and averaging for one surface bin. The accumulation procedure is done in two steps:

1. The per-track store accumulates material steps from one track/particle. Multiple material steps can be assigned to the same bin time by one particle, e.g. if the simulation has created more than one step in the material or if several components are compressed into one description. Multiple steps are treated as if they are passed one after the other.
2. The total store averages the accumulated material properties over all tracks. Each track contributes equally.

Member Function Documentation

accumulate()

void Acts::AccumulatedMaterialSlab::accumulate	(	MaterialSlab	slabAlongTrack,
		double	pathCorrection = 1. )

Add the material to the current per-track store.

Parameters

slabAlongTrack	Recorded equivalent material slab for this step
pathCorrection	Correction factor due to non-perpendicular incident

The recoded material slab is assumed to be defined along the track direction. The track can have non-perpendicular incidence on the surface and the recorded slab has to be projected along the surface normal. The path correction gives the scaling factor from normal incidence to the recorded incidence as provided by the Surface interface.

Vacuum steps with a non-zero thickness can be added to account for holes in material structures.

totalAverage()

std::pair< MaterialSlab, unsigned int > Acts::AccumulatedMaterialSlab::totalAverage

(

)

const

Return the average material properties from all accumulated tracks.

Returns

Average material properties and the number of contributing tracks

Only contains the information up to the last .trackAverage(...) call. If there have been additional calls to .accumulate(...) afterwards, the information is not part of the total average. The thickness corresponds to the average thickness seen by the tracks.

totalVariance()

std::pair< float, unsigned int > Acts::AccumulatedMaterialSlab::totalVariance

(

)

const

Return the material variance from all accumulated tracks.

Returns

Average material properties and the number of contributing tracks

Only contains the information up to the last .trackVariance(...) call. If there have been additional calls to .accumulate(...) afterwards, the information is not part of the total average. The number of tracks is only updated on the call of .trackAverage(...)

trackAverage()

void Acts::AccumulatedMaterialSlab::trackAverage

(

bool

useEmptyTrack = false

)

Add the accumulated material for the current track to the total average.

Parameters

useEmptyTrack

indicate whether to consider an empty track store

This finishes the material accumulation for the current track and resets the per-track store. Subsequent calls to .accumulate(...) will start accumulating material for a new track.

Each track contributes equally to the total average regardless of its measured path within the material. An empty per-track store, i.e. vanishing per-track material thickness, does not contribute to the total unless explicitly requested.

trackVariance()

void Acts::AccumulatedMaterialSlab::trackVariance	(	MaterialSlab	slabReference,
		bool	useEmptyTrack = false )

Use the accumulated material to update the material variance.

Parameters

slabReference	reference slab (from the map) used to compute the variance
useEmptyTrack	indicate whether to consider an empty track store

The material variance can be used to optimised the mapping process as it should be inversely proportional to the map quality