class AliKFParticleBase: public TObject

 Constructor from "cartesian" track, particle mass hypothesis should be provided

 Param[6] = { X, Y, Z, Px, Py, Pz } - position and momentum
 Cov [21] = lower-triangular part of the covariance matrix:

                (  0  .  .  .  .  . )
                (  1  2  .  .  .  . )
  Cov. matrix = (  3  4  5  .  .  . ) - numbering of covariance elements in Cov[]
                (  6  7  8  9  .  . )
                ( 10 11 12 13 14  . )
                ( 15 16 17 18 19 20 )

* Initialise covariance matrix and set current parameters to 0.0

* Set decay vertex parameters for linearisation

* Calculate particle momentum

* Calculate particle transverse momentum

* Calculate particle pseudorapidity

* Calculate particle polar angle

* Calculate distance to the origin

* Calculate particle mass

* Calculate particle decay length [cm]

* Calculate particle decay length in XY projection [cm]

* Calculate particle decay time [s]

* Get big enough correction for S error to let the particle Part be fitted to XYZ point

* Get additional covariances V used during measurement

* Energy considered as an independent veriable, fitted independently from momentum, without any constraints on mass

* Energy considered as a dependent variable, calculated from the momentum and mass hypothesis

* Energy considered as an independent variable, fitted independently from momentum, without any constraints on mass

* Set production vertex for the particle, when the particle was not used in the vertex fit

* Set nonlinear mass constraint (Mass) on the state vector mP with a covariance matrix mC.

* Set nonlinear mass constraint (mass)

* Set hard( SigmaMass=0 ) or soft (SigmaMass>0) mass constraint

* Set no decay length for resonances

* Full reconstruction in one go

* Tricky function - convert the particle error along its trajectory to
* the value which corresponds to its production/decay vertex
* It is done by combination of the error of decay length with the position errors

* Transport the particle to its decay vertex

* Transport the particle to its production vertex

* Transport the particle on dS parameter (SignedPath/Momentum)

* Get dS to a certain space point without field

* Get dS to another particle for Bz field

* Transport the particle on dS, output to P[],C[], for CBM field

* Transport the particle on dS, output to P[],C[], for Bz field

* Calculate distance from vertex [cm]

* Calculate distance from vertex [cm]

* Calculate distance to other particle [cm]

* Calculate sqrt(Chi2/ndf) deviation from vertex

* Calculate sqrt(Chi2/ndf) deviation from vertex
* v = [xyz], Cv=[Cxx,Cxy,Cyy,Cxz,Cyz,Czz]-covariance matrix

* Calculate sqrt(Chi2/ndf) deviation from other particle

* Subtract the particle from the vertex

* Transport the particle as a straight line

* Create gamma

 example:
       AliKFParticle PosParticle(...)
       AliKFParticle NegParticle(...)
       Gamma.ConstructGamma(PosParticle, NegParticle);
       Double_t VertexGamma[3] = {Gamma.GetX(), Gamma.GetY(), Gamma.GetZ()};
       PosParticle.TransportToPoint(VertexGamma);
       NegParticle.TransportToPoint(VertexGamma);
       Double_t armenterosQtAlfa[2] = {0.};
       AliKFParticle::GetArmenterosPodolanski(PosParticle, NegParticle, armenterosQtAlfa );

 Rotates the KFParticle object around OZ axis, OZ axis is set by the vertex position
 Double_t angle - angle of rotation in XY plane in [rad]
 Double_t Vtx[3] - position of the vertex in [cm]

* Invert symmetric matric stored in low-triagonal form

* Matrix multiplication Q*S*Q^T, Q - square matrix, S - symmetric

*
* ABSTRACT METHODS HAVE TO BE DEFINED IN USER CLASS
*
* Virtual method to access the magnetic field

* Virtual methods needed for particle transportation
* One can use particular implementations for collider (only Bz component)
* geometry and for fixed-target (CBM-like) geometry which are provided below
* in TRANSPORT section
* Get dS to xyz[] space point

* Get dS to other particle p (dSp for particle p also returned)

* Destructor

* Set consruction method

* Set and get mass hypothesis of the particle

* Returns the sum of masses of the daughters

*
*  ACCESSORS
*
* Simple accessors

*
*  MODIFIERS
*