To calculate a process

At first, we must prepare a directory for the process and then prepare a input files "process.def", and create subdirectory "fort" and "diagram" in the directory.

Let's start from an example $e^+ e^- \rightarrow w^+ w^- H$, which is prepared in the the fdc system directory "$fdc/example". We can prepare the inputs by perform the following command.

$>$ process_cp $fdc/example/p1 p

where the command "process_cp" is in the directory "$fdc/bin" and it creates the directory "p", copy input files "process.def" in "$fdc/example/p1" into "p", and create the subdirectory "fort" and "diagram" in "p"

The following is the detailed description of the input file "process.def":

where "namel:=...." is the list of initial and final particles and the particle name notation "ef" (electron), "efb" (position), "wb" ($w^+$), w ($w^-$) and h0 (Higgs) are defined in the in the file "particle-table" in the home directory of choose physical model. "inpl:=..." is used to distinguish the initial and final particles, in which 1 means the initial particle and -1 mean final particle. "ncorrection:='((g 0) (g3 0))$" is used to give the perturbation order, in which g and g3 mean electro-weak coupling constant and strong interaction constant respectively. "(g 0)" means leading order of "g" and "(g3 0)" means leading order of "g3". for example, if there is "(g 1)", it means beyond the leading order of "g", it will calculate the next leading order diagrams of "g".

Now it is easy to perform the following steps to finished the calculation.

There are three output files in the subdirectory "fort", which are explained in the following:

fresult.dat

is the final result

convergence.dat

is the convergence behave of the integration

plot.dat

contains all the distributions which the user asked

There are a few output files in subdirectory "diagram", in which, aa0a1, aa0a2, .... are the files contains all the Feynman amplitude data, diag1.ps, diag2.ps .... are the PS files of all the Feynman diagrams.

The example is used to calculate the total cross section with the default set in FDC system. However, there are many options could be set in the input file "process.def" by user, which are explained in section "Options for user". there are also many extra usages could be added in the input file, which are described in the section "Advanced usages".

The user can follow the same procedure as above to calculate a process. But he need to make some change in the input file according to his own need.