Reconstruction/MdcPatRec/TrkBase/include/TrkBase/TrkHelixUtils.h

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//--------------------------------------------------------------------------
// File and Version Information:
//      $Id: TrkHelixUtils.h,v 1.2 2006/03/28 01:02:36 zhangy Exp $
//
// Description:  package of utility routines for doing things to helices.
//  No data members.  I'll probably want to put this someplace else
//  eventually.
//
// Environment:
//      Software developed for the BaBar Detector at the SLAC B-Factory.
//
// Author(s): Steve Schaffner
//
//------------------------------------------------------------------------
 
#ifndef TRKHELIXUTILS_H
#define TRKHELIXUTILS_H
#include "CLHEP/Geometry/Point3D.h"
#include "CLHEP/Matrix/Matrix.h"
#include "CLHEP/Matrix/SymMatrix.h"
#include "CLHEP/Matrix/Vector.h"
#include "CLHEP/Vector/ThreeVector.h"
#include "PatBField/BField.h"
#ifndef ENABLE_BACKWARDS_COMPATIBILITY
typedef HepGeom::Point3D<double> HepPoint3D;
#endif
using CLHEP::Hep3Vector;
using CLHEP::HepMatrix;
using CLHEP::HepSymMatrix;
using CLHEP::HepVector;
using MdcPatRec::BField;
 
class TrkExchangePar;
class BesPointErr;
class BesVectorErr;
class NeutParams;
 
// Class interface //
class TrkHelixUtils {
 
public:
  TrkHelixUtils(){};
 
  // Create a helix-set from a position and a momentum.
  // Uses nominal B field to determine curvature.
  static TrkExchangePar helixFromMom( const HepPoint3D& vertex, const Hep3Vector& p,
                                      double sign, const BField& );
 
  // Does the same, but gives *real* errors on the parameters
  // (instead of a default error matrix)
  // Uses nominal B field to determine curvature.
  static TrkExchangePar helixFromMomErr( const BesPointErr& vertex, const BesVectorErr& p,
                                         const HepMatrix& cxp, double sign, const BField& );
  // Does the same but for neutrals
  static NeutParams lineFromMomErr( const BesPointErr& vertex, const BesVectorErr& p,
                                    const HepMatrix& cxp, double sign, const BField& );
 
  // Jacobian for transforming std helix params to new set defined at fltNew
  static HepMatrix jacobianExtrapolate( const TrkExchangePar&, double fltNew );
 
  // Actually transform the error matrix, as above
  static HepSymMatrix extrapolateCov( TrkExchangePar&, double fltNew );
 
  // Path length (3-d) to intersection with cylinder at radius rad.
  static double fltToRad( const TrkExchangePar& hel, double rad );
 
private:
  // Preempt
  TrkHelixUtils& operator=( const TrkHelixUtils& );
  TrkHelixUtils( const TrkHelixUtils& );
};
 
#endif