StraightLine.h

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/********************************************************************************
 * Class StraightLine.h
 * definition of the straight line at BESIII:
 * https://docbes3.ihep.ac.cn/~offlinesoftware/images/4/49/StraightLinePar.pdf
 ********************************************************************************/
#ifndef STRAIGHTLINE_H
#define STRAIGHTLINE_H
 
#include "CLHEP/Matrix/Vector.h"
#include "CLHEP/Vector/ThreeVector.h"
#include "CLHEP/Matrix/SymMatrix.h"
#include "CLHEP/Geometry/Point3D.h"
 
#ifndef ENABLE_BACKWARDS_COMPATIBILITY
//  backwards compatibility will be enabled ONLY in CLHEP 1.9
typedef HepGeom::Point3D<double> HepPoint3D;
#endif
using namespace CLHEP;
 
using namespace std;
//using namespace EventModel;
 
class StraightLine
{
    public:
        // Constructor with pivot, line parameter a
        StraightLine(const HepPoint3D & pivot,
                const HepVector & a);
 
        // Constructor with line parameter a, with default pivot (0,0,0)
        StraightLine(double dr, double phi0, double dz, double tanl);
 
        // Constructor with two points 
        StraightLine(HepPoint3D pos1, HepPoint3D pos2);
 
        /// Destructor
        virtual ~StraightLine();
 
        /// returns pivot position.
        const HepPoint3D & pivot(void) const {return m_pivot;};
 
        /// returns helix parameters.
        const HepVector & a(void) const {return m_a;};
        /// returns an element of parameters.
        double dr(void) const {return m_a[0];};
        double phi0(void) const {return m_a[1];};
        //double kappa(void) const;
        double dz(void) const {return m_a[2];};
        double tanl(void) const {return m_a[3];};
        double sinPhi0(void) const {return sin(phi0());};
        double cosPhi0(void) const {return cos(phi0());};
        double lambda() const {return atan(m_a[3]);}; 
        double theta() const {return M_PI/2.-lambda();};
        double cosTheta() const {return cos(theta());};
 
        /// returns position after moving s in downwoards
        HepPoint3D x(double s = 0.) const;
 
        // s to reach R
        double sAtR(double R, int direction=1) const;
        // position at R  or intersection with R
        HepPoint3D xAtR(double R, int direction=1) const;
 
        // s at phi
        double sAtPhi(double phi) const;
        // position at phi
        HepPoint3D xAtPhi(double phi) const;
 
 
        /// returns position and convariance matrix(Ex) after moving s.
        // HepPoint3D x(double s, HepSymMatrix & Ex) const;
 
        // modifiers
        void set(const HepVector & a);
        void set(const HepPoint3D & pivot);
        /// sets pivot position, parameters.
        void set(const HepPoint3D & pivot, const HepVector & a);
 
 
        void print();
 
    private:
        HepPoint3D m_pivot;
        HepVector m_a;// dr, phi0, dz, tanl
        //HepSymMatrix m_Ea;
        //bool m_matrixValid;
};
#endif