subroutine rtrans(gt,bt)
c---calculate gamma and beta for the transformations to and from
c---the rest frame of the bunch.
c---------------------------------------------------------------------------
c
      include 'param_sz.h'
      include 'constcom.h'
      include 'coordcom.h'
      include 'ncordscom.h'
      include 'ucom.h'
c
c--------------------------------------------------------------------------
c*
      bgb=0.
c for average gt run loop to ngood and uncomment following and line after 10
c      xnp=ngood
      do 10 n=1,1
      bgb=bgb+cord(6,n)
  10  continue
c     bgb=bgb/xnp
      gt=sqrt(1.+bgb**2)
      bt=sqrt(gt**2-1.)/gt
      return
      end
c++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*