FLUKA: escaping energy

[Dominik Dworak <dworak@alf.ifj.edu.pl>]

  Hi,
I have as simply geometry as it is possible:
   region 1 = water filled cylinder (r=60 cm, l=10 m)
   region 2 = an external vacuum surrounding this cylinder
   region 3 = blackhole surrounding vacuum.
Water in the cylinder is irradiated by 250 GeV, pencil like
electron beam.
I look for the total energy escaping out from the cylinder.
To do it I used two ways:

  1. USRBDX (one-way current estim. from reg. 1 to reg. 2)
     for FLUKA particle 208.  I have obtained:

                              E1 = 2.543 GeV

  2. SCORE option for particle 208.
     Looking at reg. 3 (blackhole) I found:

                              E2 = 2.483 GeV

     The same value E2 is printed out in FLUKA output as the
     energy escaping the system. Right.

The difference E1 - E2 = +60 MeV and it means that more energy
escapes from the cylinder than from the whole system.
It means, some of energy is "deposed" in vacuum. Strange.
Of course, the difference is not big in comparison to the beam
energy but it is much too much to be caused by rounding errors.

I thought, "maybe a reason were neutrinos:
particles like muons can escape the cylinder (their energy is
stored by USRBDX) but afterwards they decay in fly in vacuum
and neutrinos from this decay are not visible in blackhole
region as in my job all neutrinos are DISCARDed by default".

So, I "unDISCARD" all neutrinos and made the same job.
I have received:
                        E1 = 2.635 GeV
                        E2 = 2.685 GeV

This time we have opposite situation:

                       E1 - E2 = -50 MeV

and it means that some of energy is "created" in the external vacuum.

What is going on and which values are true ?
                      Regards,  Dominik Dworak, Cracow, Poland