Problem 896 - abnormal proton-nucleus scattering in Bertini cascade model
Summary: abnormal proton-nucleus scattering in Bertini cascade model
Status: RESOLVED FIXED
Alias: None
Product: Geant4
Classification: Unclassified
Component: processes/hadronic (show other problems)
Version: 8.1
Hardware: PC Linux
: P2 major
Assignee: aatos.heikkinen
URL: http://cern.ch/jemtchou/g4bug/index.html
Depends on:
Blocks:
 
Reported: 2006-10-04 11:50 CEST by zhemchugov
Modified: 2008-03-06 05:33 CET (History)
2 users (show)

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Description zhemchugov 2006-10-04 11:50:11 CEST 
An incident proton with momentum 4 GeV/c has been simulated interacting with
Berillium target (thickness 60 mm), using Bertini cascade model for hadronic
interactions (QGSP_BERT). Final state with two outgoing protons has been
selected. Distribution of invariant mass, calculated for these protons, has
abnormally high peak at 3 GeV (which corresponds to proton-proton elastic
scattering). Distribution of polar angles of protons, corresponding to the peak,
also shows strange correlation: one of protons always has polar angle equal to
20 degrees, and another one - to about 45 degrees.
Change of momentum of initial proton does not change the picture qualitatively,
as well as change of target material. The same simulation using Binary cascade
model (QGSP_BIC) shows significantly different  behavior.
Illustrating plots can be found at http://cern.ch/jemtchou/g4bug/index.html
Comment 1 zhemchugov 2008-02-11 10:46:18 CET 
Seems to disappear in 4.9.1
Comment 2 dennis.herbert.wright 2008-03-06 05:33:00 CET 
Confirmed that this was fixed by removing a bug in nucleon-nucleon scattering
angular distribution.   In version 9.1, angular distribution was changed from
nearly isotropic to exp(t).