RE: [fluka-discuss]: Question about energy loss

From: Anton Lechner <Anton.Lechner_at_cern.ch>
Date: Fri, 25 Apr 2014 17:30:01 +0000

Dear Shirley,

First of all, in FLUKA the energy is conserved on an event-by-event basis [except for low-energy neutron interactions where it is conserved on average]. There is a specific reason for your observations: since you switch on photo-nuclear interactions, there can be events where a significant amount of energy (~GeV) goes into neutrinos (decay of pions produced in the nuclear interactions); since neutrinos are then discarded they don't appear in your energy balance.

If you are interested, you can intercept the produced neutrinos on the stack (in USDRAW). By looping over all secondaries on GENSTK and matching against neutrino particle IDs, you can determine the energy of neutrinos, e.g. for muon antineutrinos:
          DO 207 INMB = 1, NP
                   IF( KPART(INMB).EQ.28 ) THEN
                      * you can then access the neutrino energy via TKI(INMB)
                   END IF
 207 CONTINUE

Apart from this, it is correct to add up the continuous energy loss along a step (sum over the DTRACK array in MGDRAW) and discrete energy depositions (RULL in ENDRAW). Note that you can also access the escaping energy via RULL (see the different ICODES in the header of of ENDRAW). One also has to take care not to double count (which could have been an issue for other users, as you mention in your Email).

BTW, you attached probably a wrong routine, since it does not sum up the energy as you describe in your Email.

Cheers, Anton





________________________________
From: Shirley Li [shirleyli.phys_at_gmail.com]
Sent: 25 April 2014 15:55
To: Anton Lechner
Cc: fluka-discuss_at_fluka.org
Subject: Re: [fluka-discuss]: Question about energy loss

Dear Anton,

I attached the input and mgdraw.f. To check the energy, I add up RULL and DTRACK and kinetic energy of particle leaving the water region to see if it's close to 10 GeV.

Thank you very much!

Best,
Shirley


On Fri, Apr 25, 2014 at 5:31 AM, Anton Lechner <Anton.Lechner_at_cern.ch<mailto:Anton.Lechner_at_cern.ch>> wrote:
Dear Shirley,

Could you please be so kind and send me your input file+routines such that I can give a look to your problem.

Thanks!
Cheers, Anton




________________________________
From: owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it> [owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it>] on behalf of Shirley Li [shirleyli.phys_at_gmail.com<mailto:shirleyli.phys_at_gmail.com>]
Sent: 24 April 2014 22:47
To: fluka-discuss_at_fluka.org<mailto:fluka-discuss_at_fluka.org>
Subject: [fluka-discuss]: Question about energy loss

Dear FLUKA users,

I'm simulating photon (electromagnetic) showers in water. The primary photon energy is 10 GeV. As a check, I want to make sure I find where the energy goes on a event-by-event basis. For every primary photon, I add up all the continuous energy loss (DTRACK) and the point energy loss (RULL), and they count for most of the energy (>99%). I also add the energies carried away by particle escaping the water region. However, for some (very small portion) primaries, the energy in DTRACK + RULL + boundary crossing is only around 7-8 GeV, compared to the total 10 GeV.

My question is where else could the energy go? Is there anything I'm missing?

I read some discussions on similar topics in the list. But, it seems like they tend to have the opposite problem, i.e., deposited energy is more than the primary energy. Also, I couldn't imagine neutron interaction or nuclear interaction affect this much energy.

Thank you very much!!
Shirley
Received on Fri Apr 25 2014 - 20:59:43 CEST

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