# Re: How to know about the energy of parent particles?

From: Hantao Jing <jinght_at_mail.ihep.ac.cn>
Date: Mon, 05 Sep 2011 21:15:13 +0800

Dear Dr. Mary Chin,
Firstly thank you very much for your suggestion!
These days, I am learn the FLUKA manual about files of
mgdraw.f, stupre.f and struprf.f, referred by
Giuseppe Battistoni.
When the proton beam bombards the target (usually carbon
target), many positive pions with low energy will swarm on the
surface of target. Because the target can slow down the pions, the
energy of pions can be at rest. If these rest pions
decay to muons, we usually call these muons the 'surface muons'. The
energy of surface muon is about 4.1MeV and 100% polarized.
Obviously, If a high energy muon slow down by the target, it energy
maybe is 4.1MeV, but not polarized. So In FLUKA simulation,
If I want to distinguish the surface muon and slow-down muon, I need to
recorder the information of parent pions for every muons.
When I can succeed on the simulation, I will share it with
every one. If I meet problem and email to you, please don't mind.
It is kind of you, thank you again.

With my best regards,
Hantao Jing
2011-9-5
Center for acelerators R&D,
Institute of High Energy Physics, China

On 2011-9-5 20:25, Mary Chin wrote:
> Hai Hantao,
>
> Have you solved your problem already? If you haven't, maybe you can tell me more... By 'surface muons' do you mean muons crossing the surface? I just want to make sure I understand your question correctly. For decays at rest, the energy of the parent = rest mass. There is indeed some kinetic energy at the step before it reaches rest mass, but those steps (made in mgdraw before the ENTRYs) are just the way Monte Carlo works -- those steps are not physical.
>
> If you would like to know whether the pion decayed in-flight or at rest, you can use ICODE to differentiate them. Decays at rest are indicated as ICODE=102.
>
> :) mary
>
>> -----Original Message-----
>> From: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-
>> discuss_at_mi.infn.it] On Behalf Of Hantao Jing
>> Sent: 02 September 2011 17:00
>> To: fluka-discuss_at_fluka.org
>> Subject: How to know about the energy of parent particles?
>>
>> Dear FLUKA experts,
>> I want to calculated the surface muons from a carbon target.
>> The surface muons decay from rest pions.
>> By examining the energy of pions, I can obtain the surface muon
>> precisely. How to know
>> about the energy of parent pions before it decay?