Introduction

GlobalTrackingRegion ( float ptMin = 1., float originRadius = 0.2,
                       float originHalfLength = 15., float originZPos = 0.,
                       bool precise = false );

Generation of hit pairs

ORCA/src/TrackerReco/TkHitPairs
HitPairGeneratorFromLayerPair.cc
HitPairGeneratorFromLayerPair.h

Generation of hit triplets

ORCA/src/TrackerReco/TkHitTriplets
HitTripletGeneratorFromPairAndLayers.cc
HitTripletGeneratorFromPairAndLayers.h

Sensitive parameters for the extrapolation of the third hit are
float dphi = 0.03;
if (fabs(dist) > 0.025) continue;

Rough prediction

ORCA/src/TrackerReco/TkHitTriplets
ThirdHitRZPrediction.cc
ThirdHitRZPrediction.h

Important parameters are
theTolerance = Margin(0.03,0.03);
theTolerance = Margin(0.02,0.02);

More accurate prediction

Fast circle fit with the conformal mapping method (article)
ORCA/src/TrackerReco/TkHitTriplets
ThirdHitPredictionFromInvParabola.cc
ThirdHitPredictionFromInvParabola.h

-- FerencSikler - 14 Mar 2006