updated documentation

doc/musrSim.tex

@@ -35,14 +35,17 @@ $^3$ ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, U.K.
 %E-mail: ksedlak@fzu.cz}
 
 \maketitle
-
+\footnotesize
+\begin{center}
+  PSI, August 12th, 2016
+\end{center}\vspace{2mm}
+\normalsize
 \abstracts{
 ``musrSim'' is a simulation program based on Geant4,
 optimised for the $\mu$SR instruments.
 This document describes some of the commands used in the user macros
 of the simulation program for the $\mu$SR instruments based on the {\sc
-Geant4}. The root output variables are also described.
-}
+Geant4}. The root output variables are also described.}
 
 %========================================================================================================
 \section{Scope of the musrSim program}
@@ -587,6 +590,21 @@ care.
         Switches off the statistical fluctuations in the ionisation losses.  Can be usefull
 	for some technical studies.  Presently works only for \emph{G4eIonisation} and
 	for \emph{G4MuIonisation}.
+\end{description}
+
+\noindent For the interaction of keV $\mu^+$ with nanometer-thin carbon foils -- as they are used in the
+low-energy $\mu^+$ beam line and spectrometer (LEM) at PSI -- two special processes have been
+defined:
+\begin{description}
+\item{\bf /musr/command process addProcess mu+ musrMuFormation -1 -1 2}\\
+        Mu formation: yield function as well as the parameters are taken from: M. Gonin, R. Kallenbach, P. Bochsler: "Charge exchange of hydrogen atoms in carbon foils at 0.4 - 120 keV", Rev.Sci.Instrum. 65 (3), March 1994.
+
+\item{\bf /musr/command process addProcess mu+ musrMuEnergyLossLandau   -1  -1 1}
+\item{\bf /musr/command SetLandauMPV 0.01}
+\item{\bf /musr/command SetLandauSigma 0.2}\\      
+      This adds to any enabled G4 energy loss process a Landau distribution with most-probable-value
+      \emph{SetLandauMPV} (keV), and width \emph{SetLandauSigma} (keV).
+
 
 %	There is one special process, combined from G4MultipleScattering and G4CoulombScattering,
 %	defined by the following command:\\