source: trunk/documents/UserDoc/UsersGuides/PhysicsReferenceManual/latex/hadronic/theory_driven/Precompound/ReactionInitialStatePM.tex

\section{Reaction initial state.}

\hspace{1.0em} The GEANT4 precompound model is considered as an extension 
of the hadron kinetic model. It gives a possibility to extend the low 
energy range of the hadron kinetic model for
nucleon-nucleus inelastic collision and it provides a "smooth" transition 
from kinetic stage of reaction described by the hadron kinetic model to 
the equilibrium stage of reaction described by the equilibrium deexcitation 
models. 

The initial information for calculation of pre-compound
nuclear stage consists from the atomic mass number $A$, charge $Z$ of residual
 nucleus, its four momentum $P_0$, 
excitation energy $U$ and number of
excitons $n$ equals the sum of number of particles $p$ (from them $p_Z$
are charged) and number of holes $h$.

At the preequilibrium stage of reaction, we following the \cite{GMT83} approach,
take into account all
possible nuclear transition the number of excitons $n$ with $\Delta n =
+2, -2, 0$ \cite{GMT83}, which defined by transition probabilities. 
 Only emmision of neutrons, protons, deutrons, thritium and helium nuclei
  are taken
into account.