In an attempt to understand pair production, I ran a trivial geometry and measured pair production cross section versus energy for the standard package and the low energy package. By observing the resulting cross section and comparing it to known values, I found that the standard package takes into account both nucleus and electric fields (as advertised in the comments in the code), while the low energy package accounts for the nucleus field only (despite the claims in the comments in G4LowEnergyGammaConversion.) The discrepancy was found in versions 4.1 and 5.0, however, the data files used by G4LowEnergyGammaConversion didn't change in the latest version (5.2). Thus, there is no reason to believe that this bug was fixed in the version 5.2. We need this bug fixed, since we are modeling gamma-ray silicon telescopes. The difference in cross sections of pair production with and without electric filed portion, is not negligible in low-Z materials (like silicon) - it can be as large as few percent. I have plots demonstrating the bug, and can e-mail it to all interested parties. (novikova@ssd5.nrl.navy.mil). Thanks, -- Elena
The problem is reassigned to a developer participating in the same experiment as the user submitting the problem. Best wishes, Maria Grazia Pia
Some solutions of the problem are under study. Some changes are needed in the cross section management for LowEnergyGammaConversion that should handle also the electric field of the electrons.
