24.3.2010 Kamil Sedlak

New variable "timeToNextEvent" added in order to simulate time differences between subsequent events.
	1)  /gun/meanarrivaltime meanArrivalTime (defines the mean time difference betweent 
                                                  the subsequent events).
        2)  timeToNextEvent - new variable written out to the root tree.

   This new variable is needed for the pile-up studies

doc/musrSim.tex

@@ -468,6 +468,12 @@ Three special volumes ``Target, M0, M1 and M2''.
 	Set the primary particle type, if it is not positive muon.  For example, the negative muons
 	are specified by ``/gun/primaryparticle mu-''.
 
+\item{\bf /gun/meanarrivaltime \emph{meanArrivalTime}}\\
+        (default: /gun/meanarrivaltime 33.33333 microsecond)\\
+        Set mean arrival time difference between two subsequent muons (at continuos beam).
+	The output variable ``timeToNextEvent'' is subsequently generated using
+	the value of \emph{meanArrivalTime} and filled into the Root tree.
+
 \item{\bf /gun/vertex \emph{x0} \emph{y0} \emph{z0} \emph{unit}}\\
 	(default: /gun/vertex 0 0 -100 mm) \\
 	Set mean values of the $x$, $y$ and $z$ coordinates of the generated particles (muons).
@@ -827,6 +833,8 @@ The list of variables that can be stored in the Root tree:
 \begin{description}
 \item{\bf runID} (Int\_t) -- run ID number.        
 \item{\bf eventID} (Int\_t) -- event ID number.
+\item{\bf timeToNextEvent} (Double\_t) -- time difference between two subsequent events (at continuous beam facility) (in $\mu$s).
+        This time difference is generated randomly using the ``meanArrivalTime'' defined in ``/gun/meanarrivaltime meanArrivalTime''.
 \item{\bf weight} (Double\_t) -- event weight.
 \item{\bf BFieldAtDecay\_Bx, BFieldAtDecay\_By, BFieldAtDecay\_Bz, BFieldAtDecay\_B3, BFieldAtDecay\_B4, BFieldAtDecay\_B5} (Double\_t) --
 	value of the 6 coordinates of the electromagnetic field at the position and time where and when the muon decayed.