|Message: Re: Strange (?) secondaries in inelastic and quasi-elastic scattering||Not Logged In (login)|
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Dear Dennis, thanks a lot for the comprehensive reply. > 1. Your first plot shows the expected peak from quasi-elastic protons. Even though the original proton is > killed, its energy is largely preserved in the model and transferred to one of the produced secondaries. The "problem" is that there is no such peak in the energy distribution of the neutrons, and one would expect also them to be kicked out in the quasi-elastic scattering with a comparable energy transfer... > 2. Again, the initial protons are killed and do not survive the interaction. In many cases it looks like > the primary survives, but it is actually a secondary. This is a Geant4 convention for hadronic interactions. Please clarify something on this: Suppose we have a primary proton that excites the nucleus and then continues on its own path. Which of the two will happen: Will the track stop or will the track continue but the particle will be tagged as a secondary? To make things a little more complicated, something that I forgot to add previously: These plots come from scattering on a carbon target of 1mm. When we go to thicker targets (up to 6cm), we do get primary protons which have been scattered inelastically! Only a handful of them, but they do exist, and their number increases with target thickness... > 4. I'm not sure what this is, but it does look artificial. Which hadronic model/physics list/Geant4 version > are you using? V. 10-00-patch-02, with QGSP-BERT 4.0 --------------------------------------------------- Hadronic Processes for proton Process: protonInelastic Model: QGSP: 12 GeV ---> 100 TeV Model: FTFP: 9.5 GeV ---> 25 GeV Model: BertiniCascade: 0 eV ---> 9.9 GeV Cr_sctns: Barashenkov-Glauber: 0 eV ---> 100 TeV Cr_sctns: Barashenkov-Glauber: 0 eV ---> 100 TeV Cr_sctns: GheishaInelastic: 0 eV ---> 100 TeV --------------------------------------------------- Our primary protons have an energy of 232MeV. When we go to longer targets, this feature moves to lower energies (as the whole distribution moves to lower energies), but only for protons. The feature stays at the same energy for neutrons, no matter the target length. I attach the relevant plot for neutrons from 1mm-thick carbon target. Also, the feature was reproduced independently by a colleague under v. 10-01-patch-02. > 5. It would depend on which model was being used, but I don't know of any such cut-off. We were speculating a probable cut-off in binding energy... Lastly, one more question about inelastic scattering: The energy distributions of secondary nucleons look like there are no discrete levels. Do you think this has to do with the activated models? something else? Many thanks, Eleni On Tue, 14 Jun 2016 18:26:14 GMT, Dennis H. Wright wrote: > Yes, quasi-elastic processes are included as inelastic in Geant4, and > the primary gets killed in the interaction. > > 1. Your first plot shows the expected peak from quasi-elastic protons. > Even though the original proton is killed, its energy is largely > preserved in the model and transferred to one of the produced > secondaries. The peak is broadened due to intra-nuclear interactions. So > no primaries survive, but one of the secondary protons has close to the > original energy. The only way to fish them out would be to select > secondaries within some energy range around the peak energy. > > 2. Again, the initial protons are killed and do not survive the > interaction. In many cases it looks like the primary survives, but it is > actually a secondary. This is a Geant4 convention for hadronic > interactions. > > 3. Currently Geant4 cannot accurately tag a quasi-elastic secondary. > Some work has been done to separate quasi-elastic from inelastic > processes, but this is not yet complete. > > 4. I'm not sure what this is, but it does look artificial. Which > hadronic model/physics list/Geant4 version are you using? > > 5. It would depend on which model was being used, but I don't know of > any such cut-off. > Attachment: http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2016/06/15/23.48-37677-3__Inel_n_E_vs_Theta.png