Warning: remember FORTAN counts from 1 and C++ counts from 0.  The information
given below refers to the FORTRAN arrays.

===============================================================================

PHEP(1,IHEP) :
    momentum in the x direction, in GeV/c.

PHEP(2,IHEP) :
    momentum in the y direction, in GeV/c.

PHEP(3,IHEP) :
    momentum in the z direction, in GeV/c.

PHEP(4,IHEP) :
    energy, in GeV.

PHEP(5,IHEP) :
    mass, in GeV/$c^2$. For space-like partons, it is allowed to use a negative mass, according to PHEP(5,IHEP) $ = -\sqrt{-m^2}$.

VHEP(1,IHEP) :
    production vertex x position, in mm.

VHEP(2,IHEP) :
    production vertex y position, in mm.

VHEP(3,IHEP) :
    production vertex z position, in mm.

VHEP(4,IHEP) :
    production time, in mm/c ( approx 3.33 x 10^{-12}s).
