|Message: Re: Bertini Model cross section tables||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)|
On Sat, 31 Mar 2012 01:16:36 GMT, Juan Pablo Velasquez wrote:
> I would like to vary the cross section values in a percentage and see > how this affects the propagation of the intra-nuclear cascade. In order > to estimate an educated variation, It would be very helpful to know what > the errors looks like.
I see. The derivation of those values long pre-dates my involvement; I'm looking for details on what you've requested. The tabulated values are taken essentially from the old (1970's era) CERN books of evaluated cross-sections for various hadrons on nucleons.
In the mean time, I'm not sure you're going to see any clear effect on cascades due to varying any individual "cross-section" value -- there are separate values for each tabulated final state (with multiplicities from 2 up to 8 or 9), in a couple of dozen bins of projectile kinetic energy.
The cascade propagation is most likely to be affected by varying the grand total cross-section (summed over all final-states) for a given projectile and kinetic energy. That value is used to compute an effective "mean free path" in each nuclear-potential zone (see G4NucleiModel::GenerateInteractionPartners), which is exponentiated and compared to a random throw.
For the pi-N interactions, the totals are tabulated separately in the tables I mentioned previously; for the K-N and hyperon-N interactions, the totals are computed as the sum of exclusive states.
-- Michael Kelsey