class AliMUONTrackExtrap: public TObject

 set field on/off flag;
 set field at the centre of the dipole

 Returns impact parameter at vertex in bending plane (cm),
 from the signed bending momentum "BendingMomentum" in bending plane (GeV/c),
 using simple values for dipole magnetic field.
 The sign of "BendingMomentum" is the sign of the charge.

 Returns signed bending momentum in bending plane (GeV/c),
 the sign being the sign of the charge for particles moving forward in Z,
 from the impact parameter "ImpactParam" at vertex in bending plane (cm),
 using simple values for dipole magnetic field.

 Track parameters linearly extrapolated to the plane at "zEnd".
 On return, results from the extrapolation are updated in trackParam.

 Track parameters and their covariances linearly extrapolated to the plane at "zEnd".
 On return, results from the extrapolation are updated in trackParam.

 Interface to track parameter extrapolation to the plane at "Z" using Helix or Rungekutta algorithm.
 On return, the track parameters resulting from the extrapolation are updated in trackParam.

 Track parameter extrapolation to the plane at "Z" using Helix algorithm.
 On return, the track parameters resulting from the extrapolation are updated in trackParam.

 Track parameter extrapolation to the plane at "Z" using Rungekutta algorithm.
 On return, the track parameters resulting from the extrapolation are updated in trackParam.

 Set vector of Geant3 parameters pointed to by "v3" from track parameters in trackParam.
 Since AliMUONTrackParam is only geometry, one uses "forwardBackward"
 to know whether the particle is going forward (+1) or backward (-1).

 Set track parameters in trackParam from Geant3 parameters pointed to by "v3",
 assumed to be calculated for forward motion in Z.
 "InverseBendingMomentum" is signed with "charge".

 Track parameters and their covariances extrapolated to the plane at "zEnd".
 On return, results from the extrapolation are updated in trackParam.

 Add to the track parameter covariances the effects of multiple Coulomb scattering
 signedPathLength must have the sign of (zOut - zIn) where all other parameters are assumed to be given at zOut.

 Correct parameters and corresponding covariances using Branson correction
 - input param are parameters and covariances at the end of absorber
 - output param are parameters and covariances at vertex
 Absorber correction parameters are supposed to be calculated at the current track z-position

 Correct parameters for energy loss and add energy loss fluctuation effect to covariances

 Parameters used to correct for Multiple Coulomb Scattering and energy loss in absorber
 Calculated assuming a linear propagation from trackXYZIn to trackXYZOut (order is important)
 pathLength: path length between trackXYZIn and trackXYZOut (cm)
 f0:         0th moment of z calculated with the inverse radiation-length distribution
 f1:         1st moment of z calculated with the inverse radiation-length distribution
 f2:         2nd moment of z calculated with the inverse radiation-length distribution
 meanRho:    average density of crossed material (g/cm3)
 totalELoss: total energy loss in absorber

 Return the angular dispersion square due to multiple Coulomb scattering
 through a material of thickness "dZ" and of radiation length "x0"
 assuming linear propagation and using the small angle approximation.

 Add to the track parameter covariances the effects of multiple Coulomb scattering
 through a material of thickness "Abs(dZ)" and of radiation length "x0"
 assuming linear propagation and using the small angle approximation.
 dZ = zOut - zIn (sign is important) and "param" is assumed to be given zOut.
 If x0 <= 0., assume dZ = pathLength/x0 and consider the material thickness as negligible.

 Main method for extrapolation to the vertex:
 Returns the track parameters and covariances resulting from the extrapolation of the current trackParam
 Changes parameters and covariances according to multiple scattering and energy loss corrections:
 if correctForMCS=kTRUE:  compute parameters using Branson correction and add correction resolution to covariances
 if correctForMCS=kFALSE: add parameter dispersion due to MCS in parameter covariances
 if correctForEnergyLoss=kTRUE:  correct parameters for energy loss and add energy loss fluctuation to covariances
 if correctForEnergyLoss=kFALSE: do nothing about energy loss

 Extrapolate track parameters to vertex, corrected for multiple scattering and energy loss effects
 Add branson correction resolution and energy loss fluctuation to parameter covariances

 Extrapolate track parameters to vertex, corrected for multiple scattering effects only
 Add branson correction resolution to parameter covariances

 Extrapolate track parameters to vertex, corrected for energy loss effects only
 Add dispersion due to multiple scattering and energy loss fluctuation to parameter covariances

 Extrapolate track parameters to vertex without multiple scattering and energy loss corrections
 Add dispersion due to multiple scattering to parameter covariances

 Calculate the total momentum energy loss in-between the track position and the vertex assuming a linear propagation

 Returns the mean total momentum energy loss of muon with total momentum='pTotal'
 in the absorber layer of lenght='pathLength', density='rho', A='atomicA' and Z='atomicZ'

 Returns the total momentum energy loss fluctuation of muon with total momentum='pTotal'
 in the absorber layer of lenght='pathLength', density='rho', A='atomicA' and Z='atomicZ'

 change coordinate system: (X, SlopeX, Y, SlopeY, q/Pyz) -> (X, SlopeX, Y, SlopeY, q*PTot)
 parameters (param) are given in the (X, SlopeX, Y, SlopeY, q/Pyz) coordinate system

 change coordinate system: (X, SlopeX, Y, SlopeY, q*PTot) -> (X, SlopeX, Y, SlopeY, q/Pyz)
 parameters (param) are given in the (X, SlopeX, Y, SlopeY, q/Pyz) coordinate system

 <pre>
    ******************************************************************
    *                                                                *
    *  Performs the tracking of one step in a magnetic field         *
    *  The trajectory is assumed to be a helix in a constant field   *
    *  taken at the mid point of the step.                           *
    *  Parameters:                                                   *
    *   input                                                        *
    *     STEP =arc length of the step asked                         *
    *     VECT =input vector (position,direction cos and momentum)   *
    *     CHARGE=  electric charge of the particle                   *
    *   output                                                       *
    *     VOUT = same as VECT after completion of the step           *
    *                                                                *
    *    ==>Called by : USER, GUSWIM                               *
    *       Author    m.hansroul  *********                          *
    *       modified  s.egli, s.v.levonian                           *
    *       modified  v.perevoztchikov
    *                                                                *
    ******************************************************************
 </pre>

 <pre>
	******************************************************************
	*								 *
	*	Tracking routine in a constant field oriented		 *
	*	along axis 3						 *
	*	Tracking is performed with a conventional		 *
	*	helix step method					 *
	*								 *
	*    ==>Called by : USER, GUSWIM				 *
	*	Authors    R.Brun, M.Hansroul  *********		 *
	*	Rewritten  V.Perevoztchikov
	*								 *
	******************************************************************
 </pre>

 <pre>
	******************************************************************
	*								 *
	*  Runge-Kutta method for tracking a particle through a magnetic *
	*  field. Uses Nystroem algorithm (See Handbook Nat. Bur. of	 *
	*  Standards, procedure 25.5.20)				 *
	*								 *
	*  Input parameters						 *
	*	CHARGE    Particle charge				 *
	*	STEP	  Step size					 *
	*	VECT	  Initial co-ords,direction cosines,momentum	 *
	*  Output parameters						 *
	*	VOUT	  Output co-ords,direction cosines,momentum	 *
	*  User routine called  					 *
	*	CALL GUFLD(X,F) 					 *
	*								 *
	*    ==>Called by : USER, GUSWIM				 *
	*	Authors    R.Brun, M.Hansroul  *********		 *
	*		   V.Perevoztchikov (CUT STEP implementation)	 *
	*								 *
	*								 *
	******************************************************************
 </pre>

 Constructor

 Destructor

 return kTRUE if the field is switched ON

 Functions
 Not implemented

 Not implemented