|Message: Re: Regarding odd-even effect in heavy-ion interaction||Not Logged In (login)|
Click on the Forum title, e.g. on the "Forums by Category" page, to read a sequence of postings to the Forum and its threads all in one page. If you are only interested in one thread or the thread following a specific posting, click the thread or the posting, which takes you to a smaller page, which contains only the part you are interested in and may be easier to navigate.
Messages are "chained" if there are only replies at the first level, i.e. 1/1.html, 1/1/1.html etc. In case of "chained" messages the message number is replaced by the icon and there is no indentation.
Inline: Display the subject line only or also the text of the posting(s); for the choice "All" the "Outline" choices are switched off.
|1||0||1||no text / full text of posting|
|2||1||All||text for level 1 only / text for All postings|
Outline: Choose the depth of the posting thread, successive toggle controls provide increasing detail.
|1||2||1||2 levels / 1 level (original posting)|
|2||3||2||3 levels / 2 levels|
|3||3||All||3 levels / all levels (all postings)|
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 dominating 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 hypernews.slac.stanford.edu message (to reply or unsubscribe) at: > http://hypernews.slac.stanford.edu/HyperNews/geant4/get/hadronprocess/1346.html > -- José Manuel Quesada Molina Departamento de Física Atómica, Molecular y Nuclear Universidad de Sevilla Apartado 1065 41080 Sevilla, Spain Tel:+34.954559508 Fax:+34.954554445 E-mail:email@example.com Personal Web:http://personal.us.es/quesada/
|Inline Depth:||Outline Depth:||Add message:|