FCFA uses PropagatorDenominator as a stand-alone

[vollous]

• Your Mathematica version

  12.1.1

• Your FeynCalc version

  9.3.1

• Did you try to reinstall FeynCalc (stable version) using the automatic installer to make sure that you have the latest bugfixes?

  Yes

• Does your Mathematica initialization file contain statements that might influence the behavior of FeynCalc? Sometimes external packages may modify `init.m` in unusual ways, causing troubles for other codes.

  $LoadAddOns = {"FeynArts"};
  << FeynCalc`
  $FAVerbose = 0;

  and SetOptions[FourVector, FeynCalcInternal -> False];

I am working on an extension of the standard model. My model was designed in FeynRules and now I am using FeynCalc patched with FeynArts. I have an additional complex field that couples with the Higgs.

Here is one of the diagrams.

When I generate the ampltide with:

decay = InsertFields[oneloop, S[1] -> {S[5], S[5]}, 
   InsertionLevel -> {Particles}, 
   Model -> NotebookDirectory[] <> "SMH2DM_FA/SMH2DM_FA", 
   GenericModel -> NotebookDirectory[] <> "SMH2DM_FA/SMH2DM_FA"];
FCFAConvert[CreateFeynAmp[decay], IncomingMomenta -> {p}, 
  OutgoingMomenta -> {k1, k2}, List -> True, LoopMomenta -> {q}, 
  ChangeDimension -> D];

I get these terms:

(...) PropagatorDenominator(k1+k2-q,MH Sqrt[Subscript[\[Xi], S(Gen5)]]) After consulting the documentation I found that the PropagatorDenominator need to be used with FeynAmpDenominator

And because of this I cant convert the amplitudes to the Passarino Veltman basis.

An additional note that might be important. When I calculate the amplitudes with just FeynArts I dont get the Subscript[\[Xi] term. The amplitude is something like: (...) PropagatorDenominator(k1+k2-q,MH)

Thank you for the help!

[vsht]

Most likely you forgot to patch the model

FAPatch[PatchModelsOnly -> True]

[vollous]

Hi, still not working.

Only by running CreateFeynAmp[decay] I get

FAFeynAmp(GraphID(Topology==1,Generic==1,Particles==1,Number==1),Integral[q1], (...) PropagatorDenominator(k1+k2-(q1),MH Sqrt[Subscript[\[Xi], S(Gen5)]]))

With no FeynAmpDenominator attached to it.

I checked and I have the same version of FeynArts in the stand-alone package and in the patched package (FeynCalc)

[vsht]

If the model is located not in FeynArts/Models, FAPatch needs to have the full directory path

FAPatch[PatchModelsOnly -> True, 
 FAModelsDirectory -> 
  FileNameJoin[{NotebookDirectory[], "MyModelDir"}]]

Upon patching, the output of CreateFeynAmp should not contain any PropagatorDenominator symbols, only FAPropagatorDenominator may appear instead. So in your case it seems that the model still didn't get patched correctly.

[vollous]

That did the trick! Thank you!