Mathematica package FeynRules allows you to create new FeynArts models that can be used for calculations using FeynCalc. FeynRules is not a part of FeynCalc and must thus be downloaded and installed separately. You can obtain your copy from the developer website.
FeynCalc contains some examples of custom FeynRules models that are located inside
FileNameJoin[{$UserBaseDirectory, "Applications", "FeynCalc", "Examples", "FeynRules"}]The XYZ.fr-file is a FeynRules model, while the
GenerateModelXYZ.m script creates a FeynArts model out of
it. The script expects FeynRules to be located in
FileNameJoin[{$UserBaseDirectory,"Applications","FeynRules"}]This means that you should be able to load FeynRules on a fresh Mathematica kernel using
$FeynRulesPath=FileNameJoin[{$UserBaseDirectory,"Applications","FeynRules"}];
<<FeynRules`;without any error messages. If this does not work, then FeynRules have not been installed properly on your computer and cannot be used.
The script GenerateModelXYZ.m must be evaluated on a
fresh Mathematica kernel. You must ensure that no other packages are
loaded, otherwise the process will most likely fail. For that you can
either evaluate Quit[] before running the commands from the
script or manually kill the kernel(s) via
Evaluation -> Quit Kernel -> .... After the script
has successfully finished you must close the kernel again. Do not try to
load FeynCalc on the same kernel, or you will run into more issues.
The new FeynArts model should be now located inside
FileNameJoin[{$UserBaseDirectory,"Applications","FeynCalc","FeynArts","Models"}]Before it can be used for calculations, it must be patched for
compatibility with FeynCalc. The patching is done by using the function
FAPatch with the option PatchModelsOnly set to
True
Models directory of
$FeynArtsDirectory, it is sufficient to evaluate
FAPatch[PatchModelsOnly -> True] after loading FeynCalc
and FeynArts in the usual way.FAPatch[PatchModelsOnly -> True, FAModelsDirectory -> "fullPathToMyModelDir"]The patching has to be done only once for each new model. However,
rerunning FAPatch[PatchModelsOnly -> True] would not do
any harm, so if you often modify existing or add new models, you might
want to keep this command in your working notebooks.
Please note that we don’t provide support on how to create or debug a particular FeynRules model. For that please consult the package manual or contact the package developers