This directory contains subroutines mainly concerned with the 
Lorentz boost. Although it can be treated if we have information
of four momentum without knowing the mass explicitly
(i.e., /fmom/ structure is enough),
we use systematically the /ptcl/ structure thoughout, in 
which we assume 4 momentum and mass are given explicitly.  
                ~~~~~~~~~~~~~~~~~~~ 
  One may suspect that mass can be derived from (4 momentum)**2
without giving it explicitly, and  for the Lorentz transformation
we even need not know the mass value.  However, if a Lorentz transormation
like  E = gamma ( E' - beta * Pz') is applied at very high energy,  
beta is almost one and E' - Pz' is so close and we lose accuracy.
In that case, we have to use approximate formula where the mass
must be given.  Mass by sqrt ((4 momenum)**2) loses also accuracy
in this case.  So our resolution on this problem is to use /ptcl/
structure always.   
  This is somewhat different from giving 4 momentum and mass
separately in subroutine calles: In that case we have to specify
the type of  mass (real*4 or real*8 or ) in the subrouines, 
so that we cannot change the declaration in  /ptcl/ structue later. 
  To make a particle with /ptcl/ structure, one may use a subroutine call,
   
     call cmkptc(code, subcode, charge, particle).



