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#ifndef _ClosestApproachInRPhi_H_
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#define _ClosestApproachInRPhi_H_
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#include "TrackingTools/PatternTools/interface/ClosestApproachOnHelices.h"
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#include "TrackingTools/TrajectoryState/interface/FreeTrajectoryState.h"
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/** Given two trajectory states, computes the two points of closest approach
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* in the transverse plane for the helices extrapolated from these states.
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* 1) computes the intersections of the circles in transverse plane.
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* Two cases: - circles have one or two intersection points;
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* - circles do not cross; the points used are
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* the points of closest approach of the two circles.
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* 2) computes the corresponding z-coordinates. In the case where
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* the circles have two intersections, the point for which
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* the z-coordinates on the 2 tracks are the closest is chosen.
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*/
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class ClosestApproachInRPhi : public ClosestApproachOnHelices {
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public:
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ClosestApproachInRPhi() {status_ = false;}
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virtual bool calculate(const TrajectoryStateOnSurface & sta,
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const TrajectoryStateOnSurface & stb);
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virtual bool calculate(const FreeTrajectoryState & sta,
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const FreeTrajectoryState & stb);
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virtual bool status() const {return status_;}
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/**
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* Returns the two PCA on the trajectories.
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*/
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virtual std::pair<GlobalPoint, GlobalPoint> points() const;
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/** Returns not only the points, but the full GlobalTrajectoryParemeters
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* at the points of closest approach */
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std::pair <GlobalTrajectoryParameters, GlobalTrajectoryParameters >
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trajectoryParameters () const;
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/** arithmetic mean of the two points of closest approach */
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virtual GlobalPoint crossingPoint() const;
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/** distance between the two points of closest approach in 3D */
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virtual float distance() const;
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/**
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* Clone method
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*/
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virtual ClosestApproachInRPhi * clone() const {
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return new ClosestApproachInRPhi(* this);
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}
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private:
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bool compute(const TrackCharge & chargeA,
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const GlobalVector & momentumA,
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const GlobalPoint & positionA,
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const TrackCharge & chargeB,
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const GlobalVector & momentumB,
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const GlobalPoint & positionB);
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// given the old Parameters, and a new GlobalPoint,
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// we return the full new GlobalTrajectoryParameters at the
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// Point.
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static GlobalTrajectoryParameters
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newTrajectory( const GlobalPoint & newpt,
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const GlobalTrajectoryParameters & oldpar, double bz);
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// Computes center coordinates and unsigned radius of circle;
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static void circleParameters(const TrackCharge& charge,
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const GlobalVector& momemtum,
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const GlobalPoint& position,
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double& xc, double& yc, double& r,
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double bz);
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// Computes crossing points of 2 circles with centres (cx_i, cy_i)
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// and unsigned radii r_i.
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// Two cases: - circles have one or two intersection points;
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// return value = 1;
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// - circles do not cross; computes point of closest approach
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// on each circle; return value = 2;
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// if the calculation fails (e.g. concentric circles), return value = 0;
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static int transverseCoord(double cxa, double cya, double ra,
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double cxb, double cyb, double rb,
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double & xg1, double & yg1,
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double & xg2, double & yg2);
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// Computes z-coordinate on helix at given transverse coordinates
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static double zCoord(const GlobalVector& mom, const GlobalPoint& pos,
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double r, double xc, double yc, double xg, double yg);
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private:
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GlobalPoint posA, posB;
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GlobalTrajectoryParameters paramA, paramB;
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double bz;
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bool status_;
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};
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#endif
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