Track finder based on Fast Hough Transformation. More...

#include <RowBasedFastHoughTransformationProcessor.h>

Inheritance diagram for marlintpc::RowBasedFastHoughTransformationProcessor:

Public Member Functions
virtual Processor *	newProcessor ()

	RowBasedFastHoughTransformationProcessor ()
	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)

bool	_useXY
	Use XY (anode plane) measurement.

bool	_useXZ
	Use XZ (drift time) measurement.

double	_centerXY
	Center of XY (anode plane) measurement.

double	_rangeXY
	Range of XY (anode plane) measurement.

double	_centerXZ
	Center of XZ (drift time) measurement.

double	_rangeXZ
	Range of XZ (drift time) measurement.

int	_minRow
	Minimal number of (correlated) rows.

float	_fracRow
	Relative minimum cube content.

int	_maxRowDiff
	Row correation parameter.

int	_maxCube
	Maximum number of (hyper) cubes to check.

int	_minLevel
	Minimum number of (hyper) cubes splittings.

int	_maxLevel
	Maximum number of (hyper) cubes splittings.

float	_effCut
	Minimum hit density (hits/tracklength)

float	_purCut
	Maximum hit density (hits/tracklength)

int	_maxHitsPerRow
	Maximum number hits per row.

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)

bool	_timePixFlag
	Is timepix data.

Detailed Description

Track finder based on Fast Hough Transformation.

Fast Hough transformation to construct tracks from space points.

The average track direction is in (local) X direction. The measured coordinates have to be shifted and rescaled to: X->u in [-1, +1], Y,Z -> v,w in [-0.5, 0.5]. The resolution in v and w should be comparable. The track projections v(u), w(u) are parametrized by series of Legendre polynomials L_i, in the (XY) bending plane up to order 2 and in the (XZ) plane with order 1.:

v(u) = a_0 * L_0(u) + a_1 * L_1(u) (+ a_2 *L_2(u))
w(u) = b_0 * L_0(u) + b_1 * L_1(u)
with L_0(u) = 1., L_1(u) = u, L_2(u) = 1.5*u*u - 0.5

The track parameters a_i, b_i are in [-0.5, +0.5] (the initial hypercube). Each space point defines 2 hyperplanes (v(u)-v_meas=0, w(u)-w_meas=0) in the 5 (or 4) dimensional parameter space (a_i, b_i) with normal vectors (L_i(u), 0.) and (0., L_i(u)). The unit normal vector is used to calculate the distance of a hyperplane to the center of a hypercube. They intersect if the absolute value of the distance times the largest component of the unit normal vector is smaller than 0.5. The root cube is recursivly split for each dimension in two child cubes. Only childs containing a minimum number of rows are considered further until the hit density in a cube is compatible with a single track. The search stops with the first found track candidate.

Extended for timepix data (allow multiple hits per row).

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: "FHTTracks")
"CenterXYMeasurement":double	Center of XY (anode plane) measurement (default 60.)
"RangeXYMeasurement":double	Range of XY (anode plane) measurement (default 200.)
"CenterXZMeasurement":double	Center of XY (drift time) measurement (default 300.)
"RangeXZMeasurement":double	Range of XY (drift time) measurement (default 600.)
"BFieldScaleFactor":double	`Optional` parameter, scales magnetic field (map), use 1.0 (default) for field ON or 0.0 for field OFF
"UseXYMeasurement":bool	`Optional` parameter, flag for using XY (anode plane) measurement (default true)
"UseXZMeasurement":bool	`Optional` parameter, flag for using XZ (drift time) measurement (default true)
"MinimumRows":int	`Optional` parameter, minimal number of (correlated) rows (default 8)
"MaximumRowDifference":int	`Optional` parameter, row correation parameter (max. distance of correlated rows) (default 1)
"FractionOfRows":float	`Optional` parameter, relative minimum cube content (rows >= fraction * (correlated) rows) (default 0.8)
"MaximumCubes":int	`Optional` parameter, maximum number of (hyper) cubes to check (default 250)
"MinimumLevel":int	`Optional` parameter, minimum number of (hyper) cubes splittings (default 5)
"MaximumLevel":int	`Optional` parameter, maximum number of (hyper) cubes splittings (default 8)
"EfficienyCut":float	`Optional` parameter, minimum hit density (hits/tracklength) (default 0.8)
"PurityCut":float	`Optional` parameter, maximum hit density (hits/tracklength) (default 1.1)
"MaxHitsPerRow":int	`Optional` parameter, mximum number of hits per row (default 1)
"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)
"TimePixFlag":bool	`Optional` parameter, is timepix data(default false)

Author: C. Kleinwort (140205)

Credits:: The processor skeleton was generated by the script createProcessor.py

Todo:

(average) track direction different from X direction ?
hit cleaning for segment creation ?
replace hard coded radial row number for timepix data ?

A detailed description is available as lcnote LC-TOOL-2014-006.

Member Function Documentation

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

virtual

Process event.

Prepare input: map of rows with vectors of hits
While sufficient input (unused (correlated) rows)

From unused hits get x range and number of (correlated) rows (row <= lastRow + _maxRowDiff)
Build hyperplanes, root cube entries (distances)
Subdivide root cube
Process candidate

Fill output collection.

References _bfieldScaleFactor, _centerXY, _centerXZ, _effCut, _encodedModuleID, _fracRow, _inputColName, _maxCube, _maxGap, _maxHitsPerRow, _maxLevel, _maxRowDiff, _minLevel, _minRow, _outputColName, _purCut, _rangeXY, _rangeXZ, _refAtPCA, _timePixFlag, _unusedCut, _useXY, _useXZ, marlintpc::rb_Segment::addHit(), marlintpc::rb_HyperCube::divide(), marlintpc::rb_Segment::fillRowMap(), marlintpc::rb_Segment::getFirstRow(), marlintpc::rb_Segment::getHitList(), marlintpc::rb_Segment::getLastRow(), marlintpc::rb_Segment::getNdf(), and marlintpc::rb_Segment::match().

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

RowBasedFastHoughTransformationProcessor.h
RowBasedFastHoughTransformationProcessor.cc

Public Member Functions

Protected Attributes

Detailed Description

Member Function Documentation