rescaling photon beam rate in hdgeant

["Mark M. Ito" <marki@jlab.org>]

Folks,

Question for y'all on hdgeant. Trying to get myself started.

In the default control.in for hdgeant, there is a comment as follows:

c If Emin is set in the BEAM card (see above), the rate of background 
photons
c is automatically rescaled as follows:
c       Rate(E_gamma > Thr)  =  Rate(E_gamma = 0.12 Gev) * K,
c where K is a scale factor calculated inside uginit.F:
c       K = 1 for Thr = 0.12 GeV,
c       K > 1 for Thr < 0.12 GeV.
c Note, K is calculated assuming the beam energies Emax = 12, Epeak = 9.

which I am finding hard to understand. What is the intent of this 
feature? What is meant by Rate(E_gamma=0.12 GeV)?

  -- Mark