Screening parameter for Coulomb scattering in G4Wentzel model?


I am puzzled with the implementation of the screening parameter, A, in G4Wentzel model.

The expression for A is given in the Physics Reference Manual (PRM) e. g. between equations (58) and (59) over there. This expression corresponds to what is usually found in the literature. I am fine with that.

However, in the implemented G4Wentzel model a different expression is used which I don’t quite understand. Specifically at line 168 of For particles other than electrons (comparing to line 169 below) there is an additional term: 1 + G4Exp(-j*j*0.001). For light target atoms (j=Z) this is approximately a factor of ~2 difference with the PRM.

What would be the origin of this additional term? I could not find any reference to it. The coefficient value (0.001) looks empirical. Maybe it was added in order to better fit experimental data from Attwood et al., NIMB 251 (2006) ?


your analysis is correct, it is an empirical function to better fit to the Attwood data. Worse to note, that screening in this form is itself a simplification.



thank you for your response.

Is there a document related to this correction?