Comparison of electron scattering algorithms in Geant4

Electron scattering algorithms in Geant4 versions 9.4 and 9.5 were benchmarked by comparing scattered distributions against previously measured values at 13 and 20 MeV, for low, intermediate, and high atomic number materials. Several scattering models were used: Versions 93 and 95 of the Urban model, with different step size limits near boundaries; Goudsmit-Saunderson multiple scattering; and single scattering. The Urban93 and Urban95 models with a large step size limit (as in the Option 0 physics list) were found to give results most closely matching the experimental results. Scattered distributions using the Urban models were all narrower than measured by up to 6%, consistent with previous published simulations using EGSnrc. This is suggestive of a systematic difference between simulations and measurement. The magnitudes of the differences were similar to previously published results using Geant4, although there were differences in detail. In particular, the current results were typically 2% narrower than values. Results with the more restrictive step size limit in Option 3 were even more narrow, and close to those with single scattering. The Goudsmit-Saunderson multiple scattering model produced distributions up to 15% different from measured in Geant4 version 9.5 and up to 45% different in Geant4 version 9.4.