TwoTrackMinimumDistanceLineLine Class Reference

#include <TwoTrackMinimumDistanceLineLine.h>

Public Member Functions
bool	calculate (const GlobalTrajectoryParameters &, const GlobalTrajectoryParameters &)
double	firstAngle () const
std::pair< double, double >	pathLength () const
std::pair< GlobalPoint, GlobalPoint >	points () const
double	secondAngle () const

Private Attributes
GlobalPoint	gPos
GlobalPoint	hPos
double	pathG
double	pathH
double	phiG
double	phiH

Detailed Description

This is a helper class for TwoTrackMinimumDistance. No user should need direct access to this class. Exact solution.

Definition at line 17 of file TwoTrackMinimumDistanceLineLine.h.

Member Function Documentation

bool TwoTrackMinimumDistanceLineLine::calculate	(	const GlobalTrajectoryParameters &	theG,
		const GlobalTrajectoryParameters &	theH
	)

Calculates the point of closest approach on the two tracks.

Returns

false in case of success
true in case of failure. Possible failures:

• Either of the Trajectories are charged
• Either of the Trajectories is of zero momentum
• Trajectories are parallel

Definition at line 8 of file TwoTrackMinimumDistanceLineLine.cc.

References GlobalTrajectoryParameters::charge(), Vector3DBase< T, FrameTag >::dot(), gPos, hPos, MagneticField::inTesla(), PV3DBase< T, PVType, FrameType >::mag(), GlobalTrajectoryParameters::magneticField(), GlobalTrajectoryParameters::momentum(), pathG, pathH, PV3DBase< T, PVType, FrameType >::phi(), phiG, phiH, GlobalTrajectoryParameters::position(), and PV3DBase< T, PVType, FrameType >::z().

{
  GlobalPoint gOrig = theG.position();
  GlobalPoint hOrig = theH.position();
  bool isLineG = theG.magneticField().inTesla(gOrig).z() == 0 || theG.charge() == 0;
  bool isLineH = theH.magneticField().inTesla(hOrig).z() == 0 || theH.charge() == 0;
  if ( ! (isLineG && isLineH) )
  {
    edm::LogWarning ("TwoTrackMinimumDistanceLineLine")
      << "charge of input track is not zero or field non zero"
      << "\n positions: "<<gOrig<<" , "<<hOrig
      << "\n Bz fields: "<<theG.magneticField().inTesla(gOrig).z()<<" , "<<theH.magneticField().inTesla(hOrig).z()
      << "\n charges: "<<theG.charge()<<" , "<<theH.charge();
    return true;
  };

  GlobalVector gVec = theG.momentum();
  const double gMag= theG.momentum().mag(); double gMag2 = gMag*gMag;
  GlobalVector hVec = theH.momentum();
  const double hMag= theH.momentum().mag(); double hMag2 = hMag*hMag;

  if ( gMag == 0. || hMag == 0. )
  {
    edm::LogWarning ("TwoTrackMinimumDistanceLineLine")
      << "momentum of input trajectory is zero.";
    return true;
  };

  phiG = theG.momentum().phi();
  phiH = theH.momentum().phi();

  double gVec_Dot_hVec = gVec.dot(hVec);
  double norm  = gVec_Dot_hVec*gVec_Dot_hVec - gMag2*hMag2;

  if ( norm == 0 )
  {
    edm::LogWarning ("TwoTrackMinimumDistanceLineLine")
      << "Tracks are parallel.";
    return true;
  }

  GlobalVector posDiff = gOrig - hOrig;

  double tG = (posDiff.dot(gVec) * hMag2 - gVec_Dot_hVec * posDiff.dot(hVec))/ norm;
  double tH = (gVec_Dot_hVec * posDiff.dot(gVec) - posDiff.dot(hVec) * gMag2)/ norm;

  gPos = GlobalPoint ( gOrig + tG * gVec);
  hPos = GlobalPoint ( hOrig + tH * hVec);
//   cout << "TwoTrackMinimumDistanceLineLine "<<gPos<<hPos<<endl;

  pathG = tG * gMag;
  pathH = tH * hMag;
  return false;
}

double TwoTrackMinimumDistanceLineLine::firstAngle ( ) const

inline

Definition at line 35 of file TwoTrackMinimumDistanceLineLine.h.

References phiG.

{return phiG;}

std::pair< double, double > TwoTrackMinimumDistanceLineLine::pathLength

(

)

const

Definition at line 70 of file TwoTrackMinimumDistanceLineLine.cc.

References pathG, and pathH.

{
  return std::pair<double, double> ( pathG, pathH);
}

std::pair< GlobalPoint, GlobalPoint > TwoTrackMinimumDistanceLineLine::points

(

)

const

Definition at line 65 of file TwoTrackMinimumDistanceLineLine.cc.

References gPos, and hPos.

{
  return std::pair<GlobalPoint, GlobalPoint > ( gPos, hPos );
}

double TwoTrackMinimumDistanceLineLine::secondAngle ( ) const

inline

Definition at line 36 of file TwoTrackMinimumDistanceLineLine.h.

References phiH.

{return phiH;}

Member Data Documentation

GlobalPoint TwoTrackMinimumDistanceLineLine::gPos

private

Definition at line 40 of file TwoTrackMinimumDistanceLineLine.h.

Referenced by calculate(), and points().

GlobalPoint TwoTrackMinimumDistanceLineLine::hPos

private

Definition at line 40 of file TwoTrackMinimumDistanceLineLine.h.

Referenced by calculate(), and points().

double TwoTrackMinimumDistanceLineLine::pathG

private

Definition at line 39 of file TwoTrackMinimumDistanceLineLine.h.

Referenced by calculate(), and pathLength().

double TwoTrackMinimumDistanceLineLine::pathH

private

Definition at line 39 of file TwoTrackMinimumDistanceLineLine.h.

Referenced by calculate(), and pathLength().

double TwoTrackMinimumDistanceLineLine::phiG

private

Definition at line 38 of file TwoTrackMinimumDistanceLineLine.h.

Referenced by calculate(), and firstAngle().

double TwoTrackMinimumDistanceLineLine::phiH

private

Definition at line 38 of file TwoTrackMinimumDistanceLineLine.h.

Referenced by calculate(), and secondAngle().