SiliconTracking Class Reference

=== Silicon Tracking Processor ===
Processor performing stand-alone pattern recognition in the vertex detector (VTX), forward tracking disks and SIT. More...

#include <SiliconTracking.h>

Inheritance diagram for SiliconTracking:

Public Member Functions
virtual Processor *	newProcessor ()
virtual void	init ()
	Initialization.
virtual void	processRunHeader (LCRunHeader *run)
	Run header processor.
virtual void	processEvent (LCEvent *evt)
	Event processor.
virtual void	check (LCEvent *evt)
virtual void	end ()
	Called after data processing for clean up.

Protected Member Functions
int	InitialiseVTX (LCEvent *evt)
int	InitialiseFTD (LCEvent *evt)
void	ProcessOneSector (int iSectorPhi, int iSectorTheta)
void	CleanUp ()
TrackExtended *	TestTriplet (TrackerHitExtended *outerHit, TrackerHitExtended *middleHit, TrackerHitExtended *innerHit, HelixClass &helix)
int	BuildTrack (TrackerHitExtended *outerHit, TrackerHitExtended *middleHit, TrackerHitExtended *innerHit, HelixClass &helix, int innerlayer, int iPhiLow, int iPhiUp, int iTheta, int iThetaUp, TrackExtended *trackAR)
void	Sorting (TrackExtendedVec &trackVec)
void	CreateTrack (TrackExtended *trackAR)
void	AttachRemainingVTXHitsSlow ()
void	AttachRemainingFTDHitsSlow ()
void	AttachRemainingVTXHitsFast ()
void	AttachRemainingFTDHitsFast ()
void	TrackingInFTD ()
int	BuildTrackFTD (TrackExtended *trackAR, int *nLR, int iS)
int	AttachHitToTrack (TrackExtended *trackAR, TrackerHitExtended *hit)
void	FinalRefit ()

Protected Attributes
int	_nRun
int	_nEvt
int	_nDivisionsInPhi
int	_nDivisionsInTheta
int	_nLayers
int	_nLayersFTD
int	_nLayersVTX
int	_nLayersSIT
int	_nPhiFTD
std::string	_VTXHitCollection
std::string	_FTDHitCollection
std::string	_SITHitCollection
std::string	_siTrkCollection
std::string	_siTrkMCPCollection
std::vector < TrackerHitExtendedVec >	_sectors
std::vector < TrackerHitExtendedVec >	_sectorsFTD
TrackExtendedVec	_tracks5Hits
TrackExtendedVec	_tracks4Hits
TrackExtendedVec	_tracks3Hits
float	_bField
float	_chi2WRPhiTriplet
float	_chi2WRPhiQuartet
float	_chi2WRPhiSeptet
float	_chi2WZTriplet
float	_chi2WZQuartet
float	_chi2WZSeptet
float	_minDistCutAttach
int	_minimalLayerToAttach
double	PI
double	TWOPI
double	PIOVER2
double	_dPhi
double	_dTheta
double	_dPhiFTD
int	_debug
std::vector< float >	_zLayerFTD
std::vector< int >	_Combinations
std::vector< int >	_CombinationsFTD
float	_resolutionRPhiVTX
float	_resolutionZVTX
float	_resolutionRPhiFTD
float	_resolutionZFTD
float	_resolutionRPhiSIT
float	_resolutionZSIT
float	_phiCutForMerging
float	_tanlambdaCutForMerging
float	_angleCutForMerging
int	_print
int	_checkForDelta
float	_minDistToDelta
float	_distRPhi
float	_distZ
float	_chi2FitCut
float	_chi2PrefitCut
TrackExtendedVec	_trackImplVec
float	_cutOnD0
float	_cutOnZ0
float	_cutOnOmega
float	_cutOnPt
int	_minimalHits
int	_attachFast
int	_nTotalVTXHits
int	_nTotalFTDHits
int	_nTotalSITHits
int	_optFit
int	_simpleHelixFit
int	_useSIT
int	_finalRefit
int	_createMap
int	_useExtraPoint
MarlinTrackFit	_trackFit

Detailed Description

=== Silicon Tracking Processor ===
Processor performing stand-alone pattern recognition in the vertex detector (VTX), forward tracking disks and SIT.

The procedure consists of three steps :
1) Tracking in VTX and SIT ;
2) Tracking in FTD ;
3) Merging compatible track segments reconstructed in VTX and FTD
STEP 1 : TRACKING IN VTX and SIT
Algorithm starts with finding of hit triplets satisfying helix hypothesis
in three different layers. Two layers of SIT are effectively considered as outermost
layers of the vertex detector. To accelerate procedure, the 4-pi solid angle is divided in NDivisionsInTheta and NDivisionsInPhi sectors in cosQ and Phi, respectively. Triplets are looked for in 2x2 window of adjacent sectors. Once triplet is found, attempt is made to associate additional hits to track. Combinatin of hits is accepted for further analysis if the Chi2 of the fit is less than certain predefined threshold. All accepted combinations are sorted in ascending order of their Chi2. First track candidate in the sorted array is automatically accepted. The hits belonging to this track are marked as used, and track candidates sharing these hits are discarded. The procedure proceeds with increasing index of track candidate in the sorted array until all track candidate have been output or discarded.
STEP 2 : TRACKING IN FTD
In the next step tracking in FTD is performed. The strategy of tracking in the FTD is the same as used for tracking in the VTX+SIT.
STEP 3 : MERGING TRACK SEGMENTS FOUND IN FTD AND VTX+SIT
In the last step, track segments reconstructed in the FTD and VTX+SIT, belonging to the same track are identified and merged into one track. All possible pairings are tested for their compatibility. The number of pairings considered is Ntrk_VTX_SIT*Ntrk_FTD, where Ntrk_VTX_SIT is the number of track segments reconstructed in the first step in VTX+SIT (segments containing solely VTX and SIT hits) and Ntrk_FTD is the number of track segments reconstructed in the second step (segments containing solely FTD hits). Pair of segments is accepted for further examination if the angle between track segments and than certain specified threshold. Pairing satisfying this condition is subjected for addtitional test. The fit is performed on unified array of hits belonging to both segments. If the chi2 of the fit does not exceed predefined cut value two segments are unified into one track.

Input collections and prerequisites

Processor requires collection of digitized vertex, sit and ftd tracker hits.
If such a collections with the user specified names do not exist processor takes no action.

Output

Processor produces an LCIO collection of the Tracks. Each track is characterised by five parameters : Omega (signed curvuture), Tan(lambda) where lambda is the dip angle, Phi (azimuthal angle @ point of closest approach), D0 (signed impact parameter), Z0 (displacement along z axis at the point of closest approach to IP). Covariance matrix for these parameters is also provided. Only lower left corner of the covariance matrix is stored. The sequence of the covariance matrix elements assigned to track is the following:
(Omega,Omega)
(Omega,TanLambda), (TanLambda,TanLambda)
(Omega,Phi), (TanLamda,Phi), (Phi,Phi)
(Omega,D0), (TanLambda,D0), (Phi,D0), (D0,D0)
(Omega,Z0), (TanLambda,Z0), (Phi,Z0), (D0,Z0), (Z0,Z0)
The number of hits in the different subdetectors associated with each track can be accessed via method Track::getSubdetectorHitNumbers(). This method returns vector of integers :
number of VTX hits in track is the first element in this vector (Track::getSubdetectorHitNumbers()[0])
number of FTD hits in track is the second element in this vector (Track::getSubdetectorHitNumbers()[1])
number of SIT hits in track is the third element in this vector (Track::getSubdetectorHitNumbers()[2])
Output track collection has a name "SiTracks".
In addition collection of relations of the tracks to MCParticles is stored if flag CreateMap is set to 1.
Collection of relations has a name "SiTracksMCP"

Parameters

VTXHitCollectionName	name of input VTX TrackerHit collection (default parameter value : "VTXTrackerHits")
FTDHitCollectionName	name of input FTD TrackerHit collection (default parameter value : "FTDTrackerHits")
SITHitCollectionName	name of input SIT TrackerHit collection (default parameter value : "SITTrackerHits")
SiTrackCollectionName	name of the output Silicon track collection (default parameter value : "SiTracks")
SiTrackMCPRelCollection	collection name for the silicon track - MC particle relations (default parameter value : "SiTracksMCP")
LayerCombinations	combinations of layers used to search for hit triplets in VTX+SIT (default parameters : 6 4 3 6 4 2 6 3 2 5 4 3 5 4 2 5 3 2 4 3 2 4 3 1 4 2 1 3 2 1) Note that in the VTX+SIT system the first and the second layers of SIT have indicies nLayerVTX and nLayerVTX+1. Combination given above means that triplets are looked first in layers 6 4 3, and then in 6 4 2; 5 4 3; 6 3 2 etc. NOTE THAT LAYER INDEXING STARTS FROM 0. LAYER 0 is the innermost layer
LayerCombinationsFTD	combinations of layers used to search for hit triplets in FTD (default parameters 6 5 4 5 4 3 5 4 2 5 4 1 5 3 2 5 3 1 5 2 1 4 3 2 4 3 1 4 3 0 4 2 1 4 2 0 4 1 0 3 2 1 3 2 0 3 1 0 2 1 0). NOTE THAT TRACKS IN FTD ARE SEARCHED ONLY IN ONE HEMISPHERE. TRACK IS NOT ALLOWED TO HAVE HITS BOTH IN BACKWARD AND FORWARD PARTS OF FTD SIMULTANEOUSLY.
NDivisionsInPhi	Number of divisions in Phi for tracking in VTX+SIT (default value is 40)
NDivisionsInTheta	Number of divisions in cosQ for tracking in VTX+SIT (default value is 40)
NDivisionsInPhiFTD	Number of divisions in Phi for tracking in FTD (default value is 3)
Chi2WRphiTriplet	weight on chi2 in R-Phi plane for track with 3 hits (default value is 1)
Chi2WZTriplet	weight on chi2 in S-Z plane for track with 3 hits (default value is 0.5)
Chi2WRphiQuartet	weight on chi2 in R-Phi plane to accept track with 4 hits (default value is 1)
Chi2WZQuartet	weight on chi2 in S-Z plane for track with 4 hits (default value is 0.5)
Chi2WRphiSeptet	weight on chi2 in R-Phi plane for track with 5 and more hits (default value is 1)
Chi2WZSeptet	Cut on chi2 in S-Z plane for track with 5 and more hits (default value is 0.5)
Chi2FitCut	Cut on chi2/ndf to accept track candidate (default value is 100.)
Chi2PrefitCut	Chi2 Cut used in the track prefit with the simple helix hypothesis (default value is 1e+10)
AngleCutForMerging	cut on the angle between two track segments. If the angle is greater than this cut, segments are not allowed to be merged. (default value is 0.1)
MinDistCutAttach	cut on the distance (in mm) from hit to the helix. This parameter is used to decide whether hit can be attached to the track. If the distance is less than cut value. The track is refitted with a given hit being added to the list of hits already assigned for the track. Additional hit is assigned if chi2 of the new fit has good chi2. (default value is 2 )
MinLayerToAttach	the minimal layer index to attach VTX hits to the found hit triplets (default value is -1)
CutOnZ0	cut on Z0 parameter of track (in mm). If abs(Z0) is greater than the cut value, track is discarded (used to suppress fake track rate in the presence of beam induced background hits) (default value is 100)
CutOnD0	cut on D0 parameter of track (in mm). If abs(D0) is greater than the cut value, track is discarded (used to suppress fake track rate in the presence of beam induced background hits) (default value is 100)
CutOnPt	cut on Pt (GeV/c). If Pt is less than this cut, track is discarded (used to suppress fake track rate in the presence of beam induced background hits) (default value is 0.1)
MinimalHits	minimal number of hits in track required (default value is 3)
FastAttachment	if this flag is set to 1, less accurate but fast procedure to merge additional hits to tracks is used if set to 0, a more accurate, but slower procedure is invoked (default value is 0)
OptPrefit	Option for prefit of the track with simple helix model. If set to 0, helix fit based on FORTRAN code tfithl is used, when set to 1 ClusterShapes class is used to fit track with the simple helix model (default value is 0)
SimpleHelixFit	Flag to enable fast procedure of track fitting based on simple helix fit. This procedure is used when performing pattern recognition. (default value is 1)
UseSIT	When this flag is set to 1, SIT is included in pattern recognition. When this flag is set to 0, SIT is excluded from the procedure of pattern recognition (default value is 1)
FinalRefit	If set to 1, final track candidates are refitted using DELPHI fitting code, which accounts for effects of multiple scattering and energy loss (default value is 1)
CreateMap	When this flag is set to 1 collection of relations between tracks and MCParticles is created (default value is 1)
UseExtraPoint	This flag is used to steer DELPHI fitting code. If set to 0, an additional artificial mesurement point at PCA is introduced with relatively large errors. This helps to improve resolution on D0 and Z0 for fitted track. (default value 0)
Debug	flag to activate debug printout (default value 1)

Author

A. Raspereza (MPI Munich)

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

• SiliconTracking.h