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Forum: Hadronic Processes
Re: Question bug? in Be(p,n) reaction gamma spectrums using QGSP_BERT_HP and QGSP_BIC_HP has big difference (ja)
Re: None Re: bug? in Be(p,n) reaction gamma spectrums using QGSP_BERT_HP and QGSP_BIC_HP has big difference (michel maire)
Date: 02 Jan, 2014
From: Jose Manuel Quesada <Jose Manuel Quesada>

Hello Michel, sorry for the very  late reply . This an old and recurrent 
issue: I agree with Vladimir's next message on this subject: cascade 
models are not intended for such low energies. Anyhow, I guess that it's 
easy to understand what happens (which doesn't mean that we have a 
solution for it just now). In fact, although we call them "cascade 
models", the cascade model takes care of the initial stage of the 
nuclear reaction chain, namely from around ~3 GeV incident nucleon 
energy downwards until around 70-90 MeV, when preequilbrium (followed by 
de_excitation) takes over. Therefore in your case, given the very low  
energy of the incident proton, the reaction will proceed automatically 
through equilibrium de_excitation.     In other words, cascade does not 
play any role in this case since equilibrium de_excitation will directly 
be called and therefore it will be the only  mechanism into play 
(according to the sequence sequence in decreasing  energy : cascade-> 
pre-equilibrium -> de_excitation).

1) Bertini uses its own pre-quilibrium + de-excitation. If evaporation 
happens in this latter stage (as I suspect), a continuum of gammas is 
produced, as the residual excited nuclei are produced with a  
countinuous distribution of excitation energies, according to 
Weisskopf-Ewing model.

2) INCL in principle used its own de-excitation models (ABLA). Now it 
can use the same "native" G4 de_excitation models (i.e., the same than 
Binary cascade)

3) Binary uses the "native" Geant4  de_excitation models.  Now, by 
default, if the mass of the compound system is lighter than 17 (as in 
this case) Fermi Break Up model is called and just few partitions are 
allowed (according to the fragments in "Fermi Configuration list" in the 
model) . This is the reason why you see the clear peak at 3.5 MeV in the 
evaporated photons, coming evidently from the de_excitation of the 6Li 
fragment (the small fluctuations around it come from the Lorentz boost 
from CM to LAB system).

  Now, your question : which is right? Pretty sure, none of them, since, 
as Vladimir rightly states,  they are not intended for such low incident 
energies. Full quantum mechanical and  involved  models (we are in a few 
body problem @ low energies  ..) should be used, out of scope and reach  
in MC calculations (and moreover without guarantee of noticeable 
improvement) . Resorting to evaluated data would be the best option and 
this is the goal of G4ParticleHP, which is still under development. 
There are attemps of including more detailed models (as the one reported 
in this forum by S. Albright for deuteron breakup in Geant4; there has 
also been recently a deuteron breakup model included in MCNPX, etc..), 
but they are just for special cases of special interest. To my 
knowledge, no general solution nor definitive answer , I'm sorry. It's 
not necessarily a bug, is an intrinsic limitation of the models.


   Best regards

     J. M. Quesada







On 12/11/2013 05:18 PM, michel maire wrote:
> *** Discussion title: Hadronic Processes
>
> On Sun, 08 Dec 2013 09:47:51 GMT, ja wrote:
>> the gamma ray spectrum given by QGSP_BIC_HP has a strong peak at 3.5 MeV
>> due to 9 Be(p,a)6 Li, while the spectrum obtained using QGSP_BERT_HP is
>> a continues one without peak.
>>
>   I ran Hadr03 with following macro, for 3 physics constructors : bertini, qbbc (which use binary cascade) and inclxx.
>   Gamma plots confirm what you say. Log files give some informations of what happens.
>   I am not expert enough to tell you which physics is/are correct or not.
>
>   #
>   # Macro file for "Hadr03.cc"
>   #
>   /control/verbose 2
>   /run/verbose 2
>   #
>   /testhadr/det/setIsotopeMat Be9 4 9 1.85 g/cm3
>   #
>   /run/initialize
>   #
>   /gun/particle proton
>   /gun/energy 9 MeV
>   #
>   /process/list
>   /process/inactivate hadElastic
>   #
>   /analysis/setFileName jack_incl
>   /analysis/h1/set 3  100  0 5 MeV       #gamma
>   #
>   /run/beamOn 100000
>
>     Attachment:
>        http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/12/11/08.16-38652-bert.log.txt
>        http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/12/11/08.16-20040-incl.log.txt
>        http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/12/11/08.16-66731-qbbc.log.txt
>        http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/12/11/08.16-96302-bert.gif
>        http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/12/11/08.16-66894-incl.gif
>        http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/12/11/08.16-98328-qbbc.gif
>
> -------------------------------------------------------------
> Visit this GEANT4 at hypernews.slac.stanford.edu message (to reply or unsubscribe) at:
> http://hypernews.slac.stanford.edu/HyperNews/geant4/get/hadronprocess/1365/1.html  
>

-- 
José Manuel Quesada Molina
Departamento de Física Atómica, Molecular y Nuclear
Facultad de Física
Universidad de Sevilla
Apartado 1065
41080 Sevilla, España
Tel:+34.954559508
Fax:+34.954554445
http://personal.us.es/quesada/

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