Multiple scattering model
GEANT4 uses a new multiple scattering model which simulates the
scattering of the particle after a step, computes the mean path length correction
and the mean lateral displacement.
The main features of the model
are described in the
One of the most important requirement for any simulation algorithm of the
multiple scattering is that the dependence of the results on the step length
should be very weak. The MSC model used in GEANT4 fulfils this requirement.
To illustrate this electrons of energy 100 MeV have been tracked in aluminium
and the longitudinal (z) and tranverse (r) distances travelled
by the electrons have been plotted.The electrons start from z=0 and
their initial direction is that of the axis z.
In order to have a clean picture the
continuous energy loss and the multiple scattering were simulated only.
The results show a very weak dependence on the
step limit used in the simulation. (GEANT3 gives similar results.)
It should be noted that the MSC algorithms of GEANT3 and GEANT4 give
slightly different results in this simple case as it can be seen on the