#include <FastHelix.h>

Public Member Functions
	FastHelix (const GlobalPoint &outerHit, const GlobalPoint &middleHit, const GlobalPoint &aVertex, const edm::EventSetup &iSetup)

	FastHelix (const GlobalPoint &outerHit, const GlobalPoint &middleHit, const GlobalPoint &aVertex, const edm::EventSetup &iSetup, const GlobalPoint &bVertex)

FTS	helixStateAtVertex () const

bool	isValid () const

FTS	stateAtVertex () const

FTS	straightLineStateAtVertex () const

	~FastHelix ()

Private Types
typedef FreeTrajectoryState	FTS

Private Attributes
GlobalPoint	basisVertex

edm::ESHandle< MagneticField >	pSetup

GlobalVector	tesla0

FastCircle	theCircle

GlobalPoint	theMiddleHit

GlobalPoint	theOuterHit

GlobalPoint	theVertex

bool	useBasisVertex

Detailed Description

Generation of track parameters at a vertex using two hits and a vertex. It is used e.g. by a seed generator.

21.02.2001: Old FastHelix is now called FastHelixFit. Replace FastLineFit by FastLine (z0, dz/drphi calculated without vertex and errors) 14.02.2001: Replace general Circle by FastCircle. 13.02.2001: LinearFitErrorsInTwoCoordinates replaced by FastLineFit 29.11.2000: (Pascal Vanlaer) Modification of calculation of sign of px,py and change in calculation of pz, z0. 29.11.2000: (Matthias Winkler) Split stateAtVertex() in two parts (Circle is valid or not): helixStateAtVertex() and straightLineStateAtVertex()

Definition at line 27 of file FastHelix.h.

Member Typedef Documentation

typedef FreeTrajectoryState FastHelix::FTS

private

Definition at line 31 of file FastHelix.h.

Constructor & Destructor Documentation

FastHelix::FastHelix	(	const GlobalPoint &	outerHit,
		const GlobalPoint &	middleHit,
		const GlobalPoint &	aVertex,
		const edm::EventSetup &	iSetup
	)

inline

Definition at line 37 of file FastHelix.h.

References edm::EventSetup::get(), pSetup, tesla0, and useBasisVertex.

                                      : theOuterHit(outerHit),
                          theMiddleHit(middleHit),
                          theVertex(aVertex),
                          theCircle(outerHit,
                                middleHit,
                                aVertex) {
           iSetup.get<IdealMagneticFieldRecord>().get(pSetup);
           tesla0=pSetup->inTesla(GlobalPoint(0,0,0));
           useBasisVertex = false;
         }

FastHelix::FastHelix	(	const GlobalPoint &	outerHit,
		const GlobalPoint &	middleHit,
		const GlobalPoint &	aVertex,
		const edm::EventSetup &	iSetup,
		const GlobalPoint &	bVertex
	)

inline

Definition at line 52 of file FastHelix.h.

References edm::EventSetup::get(), pSetup, tesla0, and useBasisVertex.

                                     : theOuterHit(outerHit),
                           theMiddleHit(middleHit),
                           theVertex(aVertex),
                           basisVertex(bVertex),
                           theCircle(outerHit,
                                 middleHit,
                             aVertex) {
           iSetup.get<IdealMagneticFieldRecord>().get(pSetup);
           tesla0=pSetup->inTesla(GlobalPoint(0,0,0));
           useBasisVertex = true;
         }

FastHelix::~FastHelix ( )

inline

Definition at line 68 of file FastHelix.h.

68 {}

Member Function Documentation

FreeTrajectoryState FastHelix::helixStateAtVertex ( ) const

Definition at line 16 of file FastHelix.cc.

References basisVertex, funct::C, FastLine::n1(), FastCircle::n1(), FastCircle::n2(), pSetup, lumiQueryAPI::q, rho, FastCircle::rho(), mathSSE::sqrt(), tesla0, theCircle, theMiddleHit, theOuterHit, theVertex, useBasisVertex, v, PV3DBase< T, PVType, FrameType >::x(), FastCircle::x0(), PV3DBase< T, PVType, FrameType >::y(), FastCircle::y0(), and PV3DBase< T, PVType, FrameType >::z().

Referenced by stateAtVertex().

                                                         {
   
   GlobalPoint pMid(theMiddleHit);
   GlobalPoint v(theVertex);
   
   double dydx = 0., dxdy = 0.;
   double pt = 0., px = 0., py = 0.;
   
   //remember (radius rho in cm):
   //rho = 
   //100. * pt * 
   //(10./(3.*MagneticField::inTesla(GlobalPoint(0., 0., 0.)).z()));
   
   double rho = theCircle.rho();
   // pt = 0.01 * rho * (0.3*MagneticField::inTesla(GlobalPoint(0.,0.,0.)).z());
   pt = 0.01 * rho * (0.3*tesla0.z());
   //  pt = 0.01 * rho * (0.3*GlobalPoint(0.,0.,0.).MagneticField().z());
 
   // (py/px)|x=v.x() = (dy/dx)|x=v.x()
   //remember:
   //y(x) = +-sqrt(rho^2 - (x-x0)^2) + y0 
   //y(x) =  sqrt(rho^2 - (x-x0)^2) + y0  if y(x) >= y0 
   //y(x) = -sqrt(rho^2 - (x-x0)^2) + y0  if y(x) < y0
   //=> (dy/dx) = -(x-x0)/sqrt(Q)  if y(x) >= y0
   //   (dy/dx) =  (x-x0)/sqrt(Q)  if y(x) < y0
   //with Q = rho^2 - (x-x0)^2
   // Check approximate slope to determine whether to use dydx or dxdy
   // Choose the one that goes to 0 rather than infinity.
   double arg1 = rho*rho - (v.x()-theCircle.x0())*(v.x()-theCircle.x0());
   double arg2 = rho*rho - (v.y()-theCircle.y0())*(v.y()-theCircle.y0());
   if (arg1<0.0 && arg2<0.0) {
     if(fabs(theCircle.n2()) > 0.) {
       dydx = -theCircle.n1()/theCircle.n2(); //else px = 0
       px = pt/sqrt(1. + dydx*dydx);
       py = px*dydx;
     } else {
       px = 0.;
       py = pt;
     }
   } else if ( arg1>arg2 ) {
     if( v.y() > theCircle.y0() )
       dydx = -(v.x() - theCircle.x0()) / sqrt(arg1);
     else
       dydx = (v.x() - theCircle.x0()) / sqrt(arg1);
     px = pt/sqrt(1. + dydx*dydx);
     py = px*dydx;
   } else {
     if( v.x() > theCircle.x0() )
       dxdy = -(v.y() - theCircle.y0()) / sqrt(arg2);
     else
       dxdy = (v.y() - theCircle.y0()) / sqrt(arg2);
     py = pt/sqrt(1. + dxdy*dxdy);
     px = py*dxdy;
   }
   // check sign with scalar product
   if(px*(pMid.x() - v.x()) + py*(pMid.y() - v.y()) < 0.) {
     px *= -1.;
     py *= -1.;
   } 
 
   //calculate z0, pz
   //(z, R*phi) linear relation in a helix
   //with R, phi defined as radius and angle w.r.t. centre of circle
   //in transverse plane
   //pz = pT*(dz/d(R*phi)))
   
   FastLine flfit(theOuterHit, theMiddleHit, theCircle.rho());
   double dzdrphi = -flfit.n1()/flfit.n2();
   double pz = pt*dzdrphi;
   //get sign of particle
 
   GlobalVector magvtx=pSetup->inTesla(v);
   TrackCharge q = 
     ((theCircle.x0()*py - theCircle.y0()*px) / 
      (magvtx.z()) < 0.) ? 
     -1 : 1;
   
   AlgebraicSymMatrix C(5,1);
   //MP
 
   if ( useBasisVertex ) {
     return FTS(GlobalTrajectoryParameters(basisVertex, 
                           GlobalVector(px, py, pz),
                           q, 
                           &(*pSetup)), 
                CurvilinearTrajectoryError(C));
   } else {
     double z_0 = -flfit.c()/flfit.n2();
     return FTS(GlobalTrajectoryParameters(GlobalPoint(v.x(),v.y(),z_0), 
                           GlobalVector(px, py, pz),
                           q, 
                           &(*pSetup)), 
                CurvilinearTrajectoryError(C));
   }
   
 }

bool FastHelix::isValid ( void ) const

inline

Definition at line 70 of file FastHelix.h.

References FastCircle::isValid(), and theCircle.

Referenced by SiStripElectronSeedGenerator::altCheckHitsAndTSOS(), SiStripElectronSeedGenerator::checkHitsAndTSOS(), RoadSearchTrackCandidateMakerAlgorithm::initialTrajectory(), RoadSearchTrackCandidateMakerAlgorithm::initialTrajectoryFromTriplet(), and stateAtVertex().

70 {return theCircle.isValid();}

FastHelix::theCircle

FastCircle theCircle

Definition: FastHelix.h:84

FastCircle::isValid

bool isValid() const

Definition: FastCircle.h:56

FreeTrajectoryState FastHelix::stateAtVertex ( ) const

Definition at line 7 of file FastHelix.cc.

References helixStateAtVertex(), isValid(), straightLineStateAtVertex(), tesla0, and PV3DBase< T, PVType, FrameType >::z().

Referenced by SiStripElectronSeedGenerator::altCheckHitsAndTSOS(), SiStripElectronSeedGenerator::checkHitsAndTSOS(), SiStripElectronSeedGenerator::findSeedsFromCluster(), RoadSearchTrackCandidateMakerAlgorithm::initialTrajectory(), RoadSearchTrackCandidateMakerAlgorithm::initialTrajectoryFromTriplet(), SimpleCosmicBONSeeder::pqFromHelixFit(), ConvBremSeedProducer::produce(), SeedFromGenericPairOrTriplet::seedFromTriplet(), and SeedGeneratorForCosmics::seeds().

                                                    {
   
   if(isValid() && (fabs(tesla0.z()) > 1e-3))
     return helixStateAtVertex();
   else 
     return straightLineStateAtVertex();
     
 }

FreeTrajectoryState FastHelix::straightLineStateAtVertex ( ) const

Definition at line 113 of file FastHelix.cc.

References basisVertex, FastLine::c(), funct::C, FastLine::n1(), FastCircle::n1(), FastLine::n2(), FastCircle::n2(), pSetup, lumiQueryAPI::q, mathSSE::sqrt(), theCircle, theMiddleHit, theOuterHit, theVertex, useBasisVertex, v, PV3DBase< T, PVType, FrameType >::x(), and PV3DBase< T, PVType, FrameType >::y().

Referenced by stateAtVertex().

                                                                {
 
   //calculate FTS assuming straight line...
 
   GlobalPoint pMid(theMiddleHit);
   GlobalPoint v(theVertex);
 
   double dydx = 0.;
   double pt = 0., px = 0., py = 0.;
   
   if(fabs(theCircle.n1()) > 0. || fabs(theCircle.n2()) > 0.)
     pt = 1.e+4;// 10 TeV //else no pt
   if(fabs(theCircle.n2()) > 0.) {
     dydx = -theCircle.n1()/theCircle.n2(); //else px = 0 
   }
   px = pt/sqrt(1. + dydx*dydx);
   py = px*dydx;
   // check sign with scalar product
   if (px*(pMid.x() - v.x()) + py*(pMid.y() - v.y()) < 0.) {
     px *= -1.;
     py *= -1.;
   } 
 
   //calculate z_0 and pz at vertex using weighted mean
   //z = z(r) = z0 + (dz/dr)*r
   //tan(theta) = dr/dz = (dz/dr)^-1
   //theta = atan(1./dzdr)
   //p = pt/sin(theta)
   //pz = p*cos(theta) = pt/tan(theta) 
 
   FastLine flfit(theOuterHit, theMiddleHit);
   double dzdr = -flfit.n1()/flfit.n2();
   double pz = pt*dzdr; 
   
   TrackCharge q = 1;
   AlgebraicSymMatrix66 C = AlgebraicMatrixID();
   //MP
 
   if ( useBasisVertex ) {
     return FTS(GlobalTrajectoryParameters(basisVertex, 
                           GlobalVector(px, py, pz),
                           q, 
                           &(*pSetup)), 
                CartesianTrajectoryError(C));
   } else {
   double z_0 = -flfit.c()/flfit.n2();
   return FTS(GlobalTrajectoryParameters(GlobalPoint(v.x(), v.y(), z_0),
                         GlobalVector(px, py, pz),
                         q,
                         &(*pSetup)),
              CartesianTrajectoryError());
   }
 }