By R.P.Kokoulin, May 12th, 2000

Multiple Coulomb Scattering – some questions and problems

Apart from the problems of creation and development of convenient 
procedure for fast simulation of the effect, some principal questions are to be 
answered (possibly, most of them have already been investigated)

General

Is it possible to use cross section formulae without magnetic formfactor and spin effects:

a) for nucleus (probably yes);
b) for proton (possibly yes);
c) for electron (probably no).

Should the scattering on the screened nucleus and on atomic electrons be considered 
separately? (likely, they should; they probably can be combined later, but…)

Scattering on the nucleus:

a) influence of the choice of the elastic atomic formfactor (TF, HF, hydrogen-like, …); 
there is a hope that the difference is small (with a proper choice of the parameters) but 
it should be estimated;
b) influence of the nuclear size (it should influence RMS angle and distribution shape on 
the tail);
c) influence of the choice of nuclear formfactor (exponential, Gaussian, Fermi model, 
etc.); probably, it is small (only RMS nucleus radius is crucial) but it is better to 
compare directly;
d) contribution of inelastic nucleus formfactor (incoherent scattering on protons of the 
nucleus);
e) necessity of taking into account proton formfactor (for incoherent scattering); last two 
points are expected to give small effect but need evaluation.

Scattering on atomic electrons:

a) introduction and influence of the choice of inelastic atomic formfactor (TH, 
hydrogen-like exponential, what else?) – it should be evaluated; more simple 
approaches, such as Z(Z+1) substitutions, seem to be incorrect;
b) problem of a double account for scattering on electrons if explicit simulation of the 
elastic scattering of the projectile on electrons (possibly, above the cut Tcut) is 
included (knock-on electron production with full kinematics) – the possible way is to 
consider restricted multiple scattering (below Tcut).