\section{EvtGen distribution}
\label{sect:tarfile}
\index{EvtGen.tar}
\index{DECAY.DEC}
\index{evt.pdl}
\index{Makefile}

For distribution of the EvtGen source outside of the BaBar experiment
a tar file, EvtGen.tar, containing the complete source, is
available. This file can be obtained from
\begin{verbatim}
http://www.slac.stanford.edu/~lange/EvtGen 
\end{verbatim}
Here you will find the versions that are available and short descriptions
of modifications and improvements as well as known problems.  

There are a handful of files other than the source files
included in the {\tt EvtGen.tar} file.  The functionality
of the  {\tt evt.pdl}, {\tt DECAY.DEC}, 
and {\tt Makefile}
files is described below.  Additionally, a {\tt test} 
directory is included that provides several diagnostic
tests of the EvtGen library.

{\tt evt.pdl} is needed at runtime by EvtGen, as
it contains the list of particles and particle
properties to be used.  This table is fully described in
Section~\ref{sect:pdttable}.  Similarly, {\tt DECAY.DEC}
contains the default list of decay channels, including
branching ratios, as 
described in Section~\ref{sect:decaytable}.

The {\tt Makefile} is responsible for building the EvtGen library
as well as test executables.  The unpacking of EvtGen.tar 
and the use of the {\tt Makefile} are described in
Section~\ref{sect:gettingstarted}.

The directory {\tt test} contains the files necesary to
perform several tests of the EvtGen code, 
as detailed in Section~\ref{sect:gettingstarted}.

\subsection{Get started with EvtGen}
\label{sect:examples}
\label{sect:gettingstarted}
\index{Examples}
\index{Getting started with EvtGen}

After unpacking the {\tt EvtGen.tar} file, 
it is quite simple to get started with EvtGen.  This
section describes the process of compiling and
linking the code and running several simple tests.  Sample output
of these tests are shown.  Manipulating the output
of EvtGen using user decay files is also explained.

First, several envirnment variables are needed to setup
the external packages.  The list below gives the envvar
and an example setting:
\begin{enumerate}
\item CERN\_ROOT = /cern/pro
\item ROOT\_SYS = /home/lange/root
\item  CLHEP\_BASE\_DIR = /home/lange
(CLHEP in /home/lange/CLHEP and CLHEP libs in /home/lange/lib)
\end{enumerate}

To properly set up the {\tt Makefile}, type {\tt configure}.
The {\tt configure} script will ask several questions,
and then build the {\tt Makefile}.  The output of the configure
script will look something like the following:
\begin{verbatim}
lange@EvtGen>./configure
Welcome to configure for EvtGen
Deleting config.mk
This machine is running: Linux
Linux is supported.
Enter Name of c++ compiler (ie c++,cxx,CC, etc)
gcc-3.2.1
Will use gcc-3.2.1 for compilation of C++ code
Enter name of fortran comiler
f77
Will use f77 for compilation of fortran code
The EvtGen package uses photos and pythia from cernlib: Please set CERN_ROOT if not already
The EvtGen package uses root for histograming. Please set ROOTSYS if not already
The EvtGen package relies on CLHEP. Please set CLHEP_BASE_DIR if not already
Finding compiler includes

The gcc-3.2.1 compiler includes are
-Iignoring -Inonexistent -Idirectory -I"/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/include/c++" -Iignoring -Inonexistent -Idirectory -I"/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/include/c++/i686-pc-linux-gnu" -Iignoring -Inonexistent -Idirectory -I"/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/include/c++/backward" -Iignoring -Inonexistent -Idirectory -I"/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/include" -Iignoring -Inonexistent -Idirectory -I"/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/../../../../i686-pc-linux-gnu/include" -Iignoring -Inonexistent -Idirectory -I"/afs/slac.stanford.edu/package/gcc/gcc-3.2/3.2.1/i386_linux24/i686-pc-linux-gnu/include" -I/afs/slac.stanford.edu/package/gcc/gcc-3.2/3.2.1/i386_linux24/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/include/c++ -I/afs/slac.stanford.edu/package/gcc/gcc-3.2/3.2.1/i386_linux24/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/include/c++/i686-pc-linux-gnu -I/afs/slac.stanford.edu/package/gcc/gcc-3.2/3.2.1/i386_linux24/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/include/c++/backward -I/usr/local/include -I/afs/slac.stanford.edu/package/gcc/gcc-3.2/3.2.1/i386_linux24/include -I/afs/slac.stanford.edu/package/gcc/gcc-3.2/3.2.1/i386_linux24/lib/gcc-lib/i686-pc-linux-gnu/3.2.1/include -I/usr/include
The default gcc-3.2.1 options are 
-I. -DEVTSTANDALONE
Enter any other options that you would like
to use in compilation.  Examples -g -pg -o4 etc
The following options will be used by default
-I. -DEVTSTANDALONE
The default link options are  
for the test program.
Please enter any others that you would like to use

Done. Type gmake lib then gmake bin
\end{verbatim}

The {\tt configure} script builds a file
called {\tt config.mk} that is included by the {\tt Makefile}.

To build the EvtGen libary simply type {\tt gmake} in
the {\tt EvtGen} directory.  This should compile each
{\tt .cc} file and make a library called {\tt libEvtGen.a}.  If
this fails to compile on your platform, please contact the
authors for help.  

To compile EvtGen with no changes, the
JETSET~\cite{jetset} 
and PHOTOS~\cite{Was92} packages from CERNLIB are needed, as well
as the CLHEP~\cite{clhep} and ROOT~\cite{root} packages.  
A version of {\tt lucomp.F} is included that defines 
additional particles used by EvtGen. 
The
dependence on ROOT is solely for the histograming 
performed in the {\tt testEvtGen} test program.  If you do not \
need this feature it is easy to eliminate this dependence. 

The most recent version has been tested using gcc-3.2.1, CERNLIB 2000,
CLHEP 1.8.0.0, and ROOT 3.01.02.  The only change from the
default installations is that a softlink to libCLHEP.a was
created to libCLHEP-g++.a.  The need for this change can be eliminated by
changing the {\tt Makefile} in EvtGen.

If the library was built successfully, type {\tt gmake bin}
in order to build a sample executable (called {\tt testEvtGen}).  With
this executable, several tests of the EvtGen library may
be performed to check that the code is working properly.  To 
do these type
\begin{verbatim}
cd test
../testEvtGen test1 20000
../testEvtGen ddalitz 20000
\end{verbatim}
The {\tt test} directory should now contain {\tt test1.root} and
{\tt ddalitz.root}, each of which are ROOT files containing
several histograms.  Figures~\ref{fig:test1} and~\ref{fig:ddalitz}
show some of these histograms.  These Figures can be 
reproduced using {\tt test1-root.script} and
{\tt ddalitz-root.script}.

\begin{figure}
\epsfig{figure=elep1.eps,width=\linewidth}
\caption{Histogram number 3 in {\tt test1.root} for 1000 events shows
the lepton energy in the $B\rightarrow D^{*}\ell\nu$ decay.}
\label{fig:test1}
\end{figure}

\begin{figure}
\epsfig{figure=ddalitz1.eps,width=\linewidth}
\caption{Histogram number 1 in {\tt ddalitz.root} for 20000 event shows
the dalitz plot for the $D\rightarrow K\pi\pi$ decay.}
\label{fig:ddalitz}
\end{figure}