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#ifndef _Tracker_TwoTrackMinimumDistanceHelixLine_H_
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#define _Tracker_TwoTrackMinimumDistanceHelixLine_H_
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#include "DataFormats/GeometryVector/interface/GlobalPoint.h"
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#include "DataFormats/GeometryVector/interface/GlobalVector.h"
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#include <utility>
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/** \class TwoTrackMinimumDistanceHelixLine
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* This is a helper class for TwoTrackMinimumDistance, for the
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* case where one of the tracks is charged and the other not.
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* No user should need direct access to this class.
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* It implements a Newton method
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* for finding the minimum distance between two tracks.
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*/
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class GlobalTrajectoryParameters;
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class TwoTrackMinimumDistanceHelixLine {
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public:
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TwoTrackMinimumDistanceHelixLine(): theH(0), theL(0), themaxiter(12),
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pointsUpdated(false){}
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~TwoTrackMinimumDistanceHelixLine() {}
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/**
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* Calculates the PCA between a charged particle (helix) and a neutral
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* particle (line). The order of the trajectories (helix-line or line-helix)
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* is irrelevent, and will be conserved.
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*/
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bool calculate( const GlobalTrajectoryParameters &,
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const GlobalTrajectoryParameters &,
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const float qual=.0001 ); // retval=true? error occured.
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/**
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* Returns the PCA's on the two trajectories. The first point lies on the
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* first trajectory, the second point on the second trajectory.
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*/
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std::pair <GlobalPoint, GlobalPoint> points() const;
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std::pair <double, double> pathLength() const;
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double firstAngle() const;
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double secondAngle() const;
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private:
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GlobalTrajectoryParameters *theH, *theL, *firstGTP, *secondGTP;
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GlobalVector posDiff;
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GlobalVector theLp;
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double X, Y, Z, px, py, pz, px2, py2, pz2, baseFct, baseDer;
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double theh, thePhiH0, thesinPhiH0, thecosPhiH0, thetanlambdaH;
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double thePhiH;
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double Hn, Ln;
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double aa,bb,cc,dd,ee,ff;
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int themaxiter;
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bool updateCoeffs();
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void finalPoints() const;
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bool oneIteration(double & thePhiH, double & fct, double & derivative ) const;
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mutable GlobalPoint helixPoint, linePoint;
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mutable double tL, linePath, helixPath;
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mutable bool pointsUpdated;
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};
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#endif
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