%\subsection{Pauli blocking simulation\editor{Gunter}}

The cross sections used in this model are cross sections for free particles. In
the nucleus these cross sections are reduced to effective cross sections by
Pauli-blocking due to Fermi statistics.

 For nucleons created by a collision, ie. an inelastic
scattering or from decay, we check that all secondary nucleons occupy a state
allowed by Fermi statistics. We assume that the nucleus in its ground state and
all states below Fermi energy are occupied. All secondary nucleons  therefore
must have a momentum $p_i$ above local Fermi momentum $p_F(r)$, i.e.
\begin{equation}
p_i > p_F^{max}(r).
\end{equation}

If any of the nucleons of the collision has a momentum below the local Fermi
momentum, then the collision is Pauli blocked.  The reaction products are
discarded, and the original particles continue the cascade.
