Message: Re: Regarding odd-even effect in heavy-ion interaction Not Logged In (login)
 Next-in-Thread Next-in-Thread
 Next-in-Forum Next-in-Forum

None Re: Regarding odd-even effect in heavy-ion interaction 

Forum: Hadronic Processes
Re: Question Regarding odd-even effect in heavy-ion interaction (Summit)
Date: 27 Jul, 2013
From: Jose Manuel Quesada <Jose Manuel Quesada>

   Dear Summit,

                             it's a matter of the physics included in 
such models: one should never expect what is beyond
their capabilities.  WilsonAbrasion model is a quite simplistic one, 
based in geometry and kinematics (geometric abrasion as initial stage 
followed by ablation,
emulating de-excitation).   If no pairing effects are included, detailed 
nuclear structure effects (as the odd-even effect) shoudn't   be expected
to be described. BIC and QMD use the same  models for the final 
de-excitation stage (where the pairing effects, and therefore the 
odd-even effects,
are included),   although their initial stages are  different: BIC is a 
intranuclear cascade model , whereas QMD is a quantum molecular dymamics 
one, with more physical content in it.   As for de-excitation, 
evaporation and fission  include pairing effects, but not the 
statistical  models  (Fermi break-up and statistical multifragmentation).
Fermi break-up can be activated or not (if yes, it takes care of 
de-excitation of light fragments, Z<9, A<17), this is
a user's choice (although in the latest releases it is on by default). 
If evaporation model plays its role, this would explain
why QMD is  partially  describes the odd-even effects  (for instance 
Ar+C @  8.5 GeV/u, page 18 of A. Ivanchenko's presentation).
On the other hand, BIC largely fails to describe the odd-even effects: 
that could be due to higher excitation energies in the population of
nuclei to be de-excited by evaporation (which would wash-out to some 
extent the  structure effects) with respect to the QMD case  or a 
role of Fermi break-up model for light fragment de-excitations.  But let 
me state once again that both, QMD and BIC, use in principle
the same de-excitation models.

  As for the suppresion of Z=9, this should come from the binding 
energies  (i.e. masses) of these nuclei (helped by pairing energies, if 
evaporation mechanism is the responsible), which make the probabilities 
for de-excitation chains ending up there , small. In this case these, 
the  models are  capable of reproducing experimental behaviour.

  Best regards

                          José Manuel

On 07/26/2013 08:16 AM, Summit wrote:
> *** Discussion title: Hadronic Processes
> Dear G4Users,
> I have tried to calculate partial fragmentation cross sections for 28Si
> + Pb using G4BinaryLightIonReaction, G4WilsonAbrasion and G4QMDReaction
> models. In the simulation work, no models exactly shows the odd-even
> effect as shown by experimental data. But BIC and QMD models well show
> the suppression for the fragment with the charge Z = 9. I have seen
> similar behavior in other interactions also. I need the explanation why
> they are not able to able the exactly odd-even effect and why they have
> show the suppression as shown by experimental data?
> Also in the presentation of A.Ivantchenko (Validation of Geant4 models
> with Ion/Ion interactions, page 18-21), similar type of behavior has
> been observed.
> Can anyone give me explanation regarding this?
> Thanking you,
> Summit.
> -------------------------------------------------------------
> Visit this GEANT4 at message (to reply or unsubscribe) at:

José Manuel Quesada Molina
Departamento de Física Atómica, Molecular y Nuclear
Universidad de Sevilla
Apartado 1065
41080 Sevilla, Spain
Personal Web:

Inline Depth:
 1 1
 All All
Outline Depth:
 1 1
 2 2
 All All
Add message: (add)

1 Question: Re: Regarding odd-even effect in heavy-ion interaction   (Summit - 29 Jul, 2013)
 Add Message Add Message
to: "Re: Regarding odd-even effect in heavy-ion interaction"

 Subscribe Subscribe

This site runs SLAC HyperNews version 1.11-slac-98, derived from the original HyperNews

[ Geant 4 Home | Geant 4 HyperNews | Search | Request New Forum | Feedback ]