This directory contains example calculations with
FeynArts and FormCalc.

The files in this directory are named in the following way:

  PROCESS-MODEL.m	   -- the Mathematica program that
			      generates the Fortran code,

  PROCESS-MODEL.drivers/   -- the directory with customized
			      (process-specific) versions of
			      the driver programs,

  PROCESS-MODEL.fortran/   -- the directory which will be
			      created by PROCESS-MODEL.m
			      and in which the generated
			      Fortran code is put.

Currently, PROCESS is one of

  eett    -- e^+ e^- -> t-bar t
  eettA   -- e^+ e^- -> t-bar t gamma (hard bremsstrahlung for eett)
  eeWW    -- e^+ e^- -> W^+ W^-
  eeHH    -- e^+ e^- -> H^+ H^-
  AAAA    -- gamma gamma -> gamma gamma
  AAtt    -- gamma gamma -> t-bar t
  AAttA   -- gamma gamma -> t-bar t gamma (hard bremsstrahlung for AAtt)
  WWWW    -- W^+ W^- -> W^+ W^-
  ZZZZ    -- Z Z -> Z Z

and MODEL is the FeynArts model-file name minus the ".mod", i.e.

  SM      -- the electroweak Standard Model
  SMbgf   -- the same in the background-field formulation
  MSSM    -- the Minimal Supersymmetric Standard Model

The Fortran code for these processes can also be
obtained from www.hep-processes.de.


To execute the demo programs you need

> Mathematica 5 or higher

> FORM 3.2 or higher
  (available from http://www.nikhef.nl/~form)

> FeynArts 3.2 or higher
  (available from http://www.feynarts.de)

> LoopTools 2.2 or higher
  (available from http://www.feynarts.de/looptools)

> GNU make 3.80 or higher
  (available e.g. from http://www.gnu.org/directory/GNU/make.html)

> a Fortran-77 compiler (g77 if you don't have any other)

> for plotting the results: gnuplot 3.7 or higher
  (available from http://www.gnuplot.info)


The demo programs are invoked as follows:

Please do have a look at PROCESS-MODEL.m to see what it's doing,
whether e.g. some diagrams are left out or similar things.

Start Mathematica and type
	<< PROCESS-MODEL.m

After the program has finished, quit Mathematica and change into the
directory PROCESS-MODEL.fortran.  You may want to look into run.F or 
model.h for changing some of the parameters.  Then type
	./configure
	make
to compile the Fortran code.  The resulting executable will be called
run.  For several runs, place the parameters for each in a separate
file, say run1.F, run2.F, ..., and say "make run1", "make run2" etc.

Run "run" with the following parameters:
	./run <p1>...<pN> <sqrtS_from>,<sqrtS_to>
where the <pi> are the polarizations of the external particles.
E.g. to obtain an unpolarized differential cross-section at
Sqrt[s] = 500 GeV use
	./run uuuu 500
This creates a subdirectory called run.UUUU.00500 with the
output files.  Extract the "real" data from those (log)files using
	./data run.UUUU.00500
which results in a file run.UUUU.00500.data.  The data are
organized in columns, where column 1 is the ordinate data (angle
for a differential cross-section, Sqrt[S] for a total), column 2
is the Born cross-section, column 3 is the one-loop correction.
If present, columns 4 and 5 contain the integration errors for
columns 2 and 3, respectively.

If you have gnuplot 3.7 (or higher) installed, it is very easy to
plot the results.  Invoke e.g.
	./pnuglot run.UUUU.00500.data
It is important to understand that pnuglot does not make the plot
directly.  Rather, it writes out a shell script to do this
(run.UUUU.00500.gpl) which it then executes to produce the actual
plot (run.UUUU.00500.eps).  The advantage of this extra level of 
indirection is that if you're not completely satisfied with the
gnuplot commands pnuglot puts into the script by default, you can
easily edit run.UUUU.00500.gpl and change whatever you like.  Then
run the .gpl script (not pnuglot!) from the shell prompt to update
the .eps file:
	./run.UUUU.00500.gpl


Send bug reports, omissions, fan mail etc. to
Thomas Hahn <hahn@feynarts.de>

Have fun!

