/data/refman/pasoursint/CMSSW_5_2_9/src/RecoEgamma/EgammaPhotonAlgos/interface/TangentApproachInRPhi.h

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#ifndef _TangentApproachInRPhi_H_
#define _TangentApproachInRPhi_H_

#include "TrackingTools/PatternTools/interface/ClosestApproachOnHelices.h"
#include "TrackingTools/TrajectoryState/interface/FreeTrajectoryState.h" 

class TangentApproachInRPhi : public ClosestApproachOnHelices {

public:

  TangentApproachInRPhi() {status_ = false; intersection_ = false;}

  virtual bool calculate(const TrajectoryStateOnSurface & sta, 
         const TrajectoryStateOnSurface & stb);

  virtual bool calculate(const FreeTrajectoryState & sta,
        const FreeTrajectoryState & stb);

  virtual bool status() const {return status_;}

  virtual std::pair<GlobalPoint, GlobalPoint> points() const;

  std::pair <GlobalTrajectoryParameters, GlobalTrajectoryParameters >
        trajectoryParameters () const;

  virtual GlobalPoint crossingPoint() const;

  virtual float distance() const;
  
  float perpdist() const;

  virtual TangentApproachInRPhi * clone() const {
    return new TangentApproachInRPhi(* this);
  }

private:

  bool calculate(const TrackCharge & chargeA, 
                                        const GlobalVector & momentumA, 
                                        const GlobalPoint & positionA, 
                                        const TrackCharge & chargeB, 
                                        const GlobalVector & momentumB, 
                                        const GlobalPoint & positionB,
                                        const MagneticField& magField);

  // given the old Parameters, and a new GlobalPoint,
  // we return the full new GlobalTrajectoryParameters at the
  // Point.
  GlobalTrajectoryParameters trajectoryParameters ( const GlobalPoint & newpt,
        const GlobalTrajectoryParameters & oldpar ) const;

  // Computes center coordinates and unsigned radius of circle;
  void circleParameters(const TrackCharge& charge, 
                        const GlobalVector& momemtum, 
                        const GlobalPoint& position, 
                        double& xc, double& yc, double& r,
                        const MagneticField& magField) const;

  // Computes crossing points of 2 circles with centres (cx_i, cy_i) 
  // and unsigned radii r_i. 
  // Two cases: - circles have one or two intersection points; 
  //              return value = 1; 
  //            - circles do not cross; computes point of closest approach 
  //              on each circle; return value = 2;
  // if the calculation fails (e.g. concentric circles), return value = 0;

  int transverseCoord(double cxa, double cya, double ra, 
                      double cxb, double cyb, double rb, 
                      double & xg1, double & yg1, 
                      double & xg2, double & yg2) const;

  // Computes z-coordinate on helix at given transverse coordinates
  double zCoord(const GlobalVector& mom, const GlobalPoint& pos, 
                double r, double xc, double yc, double xg, double yg) const;


private:
  bool status_;
  GlobalPoint posA, posB;
  GlobalTrajectoryParameters paramA, paramB;
  bool intersection_;

};

#endif