marlintpc::RowTripletBasedTrackFinderProcessor Class Reference

Track finder based on triplets of rows. More...

#include <RowTripletBasedTrackFinderProcessor.h>

Inheritance diagram for marlintpc::RowTripletBasedTrackFinderProcessor:

Public Member Functions
virtual Processor *	newProcessor ()
	RowTripletBasedTrackFinderProcessor ()
	Construct processor.
virtual void	init ()
	Initialize processor.
virtual void	processRunHeader (EVENT::LCRunHeader *run)
virtual void	processEvent (EVENT::LCEvent *evt)
	Process event. More...
virtual void	check (EVENT::LCEvent *evt)
virtual void	end ()

Protected Attributes
std::string	_inputColName
	Name of the input collection.
std::string	_outputColName
	Name of the output collection.
double	_bfieldScaleFactor
	scale factor for magnetic field (default: 1.0)
double	_distCut
	Coarse cut on XY and Z residuals for triplet preselection.
double	_trpCut
	Chi2 cut for triplet definition on XY and Z residuals.
double	_posCut
	Chi2 cut for triplet position matching in XY and Z.
double	_dirCut
	Chi2 cut for triplet direction matching in XY and Z.
double	_segCut
	Chi2/Ndf cut for segment matching (Ndf=4 for B off, 5 for B on)
double	_unusedCut
	Chi2 cut for matching unused hits in XY and Z.
int	_maxGap
	Cut for (row) distance to segment for matching unused hits in XY and Z.
bool	_encodedModuleID
	Module ID is encoded in CellID0.
bool	_refAtPCA
	Use Pca as reference point (else 1. hit)

Detailed Description

Track finder based on triplets of rows.

Inspired by H1 pattern recognition by V. Blobel (Univ. Hamburg).

Input are the (position, measurement direction and errors) of the TPC hits and module parameters (offset and extend) from GEAR.

In each module (with hits):

• Triplets of hits in adjacent even or odd rows are constructed
• Triplets matching in position and direction are connected to segments
• Segments with compatible track parameters are merged
• Unused hits are added to matching segments

Segments from each module are combined with compatible segments from the corresponding neighbouring modules to build track candidates. As reference point for the track canidates the first hit is used (optional: PCA).

The hits on the track candidates are ordered by row number, no multiple hits in a row are allowed. All matching criteria use chi2 cuts based on the hit measurement errors. The calculation of the measurement (pad) direction in XY uses "module.getLocalPadLayout().getCoordinateType()" to select polar or cartesian pad row geometry.

Parameters

"InputHits":string	The name of the input collection of TPC hits (default: "TPCHits")
"OutputTracks":string	The name of the output collection with the found tracks (default: "TripletTracks")
"BFieldScaleFactor":double	Optional parameter, scales magnetic field (map), use 1.0 (default) for field ON or 0.0 for field OFF
"TripletPreSelectionDistCut":double	Optional parameter, coarse cut on XY and Z residuals for triplet preselection (default 10.)
"TripletDefinitionChi2Cut":double	Optional parameter, Chi2 cut for triplet definition on XY and Z residuals (default 20.)
"TripletPositionMatchingChi2Cut":double	Optional parameter, Chi2 cut for triplet position matching in XY and Z (default 20.)
"TripletDirectionMatchingChi2Cut":double	Optional parameter, Chi2 cut for triplet direction matching in XY and Z (default 20.)
"SegmentMatchingChi2Cut":double	Optional parameter, Chi2/Ndf cut for segment matching (Ndf=4 for B off, 5 for B on) (default 30.)
"UnusedHitMatchingChi2Cut":double	Optional parameter, Chi2 cut for matching unused hits in XY and Z (default 20.)
"UnusedHitMaxGapCut:int	Optional parameter, maximal (row) gap for matching unused hits in XY and Z (default 4)
"EncodedModuleID":bool	Optional parameter, flag for encoding of module ID in CellID0 (default true)
"ReferencePointAtPca":bool	Optional parameter, use PCA as reference point, else 1. hit (default false)

Author

C. Kleinwort (130729)

Credits:

The processor skeleton was generated by the script createProcessor.py

Todo:

• definition of module neighbourhood from POLAR module extend ?
• better resolve equivalent (indirectly matching) overlapping segments ?

A detailed description is available as lcnote LC-TOOL-2014-004. Changes with respect to this note:

• Triplet measurement direction is average of outer hits instead of center hit (, already used for doublets).
• Segment fit is iterated as weights depend on track direction (due to radial hit error).

Member Function Documentation

void marlintpc::RowTripletBasedTrackFinderProcessor::processEvent ( EVENT::LCEvent *  evt )

virtual

Process event.

• Prepare input: map of modules with maps of rows with vectors of hits
• For each module independently build track segments from triplets.

1. Look for triplets.
2. Look for segments = triplet chains.
3. Link segments (in module).
4. Link unused hits to segments.

• Link segments between modules.
• Fill output collection.

References _bfieldScaleFactor, _dirCut, _distCut, _encodedModuleID, _inputColName, _maxGap, _outputColName, _posCut, _refAtPCA, _segCut, _trpCut, _unusedCut, marlintpc::simpleEquiClasses::addIndex(), marlintpc::simpleEquiClasses::addMatch(), marlintpc::simpleEquiClasses::getClasses(), marlintpc::rb_Segment::getNdf(), and marlintpc::rb_Doublet::match().

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

• RowTripletBasedTrackFinderProcessor.h
• RowTripletBasedTrackFinderProcessor.cc