regarding extracting feynarts model using feynrules for higher dimension operators, the problem with coupling dimensionality

[dishabhatia26]

Hello,

I want to calculate the amplitudes for certain higher dimensional operators using feyncalc through the usage of feynarts.

I was using two effective field operators to test this: One is
L6= cw3 Block[{mu, nu, ro},
ExpandIndices[
FS[W, mu, nu] FS[Wbar, nu, ro] FS[B, ro, mu]];

with this I generated Feynarts output using the command:

The couplings generated by feynrules here in the dim6.mod looks like:

(* Couplings (calculated by FeynRules) *)

M$CouplingMatrices = {

C[ V[1] , V[3] , -V[3] ] == {{-gc1, 0}, {gc1, 0}, {-gc1, 0}, {gc1, 0}, {gc1, 0}, {-gc1, 0}, {-gc1, 0}, {gc1, 0}},

C[ V[3] , -V[3] , V[2] ] == {{-gc2, 0}, {gc2, 0}, {-gc2, 0}, {gc2, 0}, {gc2, 0}, {-gc2, 0}, {-gc2, 0}, {gc2, 0}}

}

with
M$FACouplings = {
gc1 -> -(cwcw3),
gc2 -> cw3sw};

Then I enter feyncalc to perform scattering calculation for the process by
generating diagrams using feynarts
diags = InsertFields[CreateTopologies[0, 2 -> 2], {V[3], -V[3]} ->
{V[1], V[1]}, Model->{"SM","dim6"},InsertionLevel -> {Classes}];

Paint[diags, ColumnsXRows -> {2, 1}, Numbering -> Simple,
SheetHeader->None,ImageSize->{512,256}];

However I get an error regarding coupling dimensions:
Coupling definition in model file for C[V(1),V(3),-V(3)] is
incompatible to generic coupling structure. Coupling is not a vector
of length 1

I repeat the same process with dimension-8 operator:
L8= cw4 Block[{mu, nu, ro,ro1},
ExpandIndices[
FS[W, mu, nu] FS[Wbar, mu, nu] FS[W, ro, ro1] FS[Wbar, ro,ro1]];

The coupling in dim8.mod looks like:

(* Couplings (calculated by FeynRules) *)

M$CouplingMatrices = {

C[ V[3] , V[3] , -V[3] , -V[3] ] == {{gc1, 0}, {gc1, 0}, {-gc1, 0}, {-gc1, 0}, {-gc1, 0}, {gc1, 0}, {-gc1, 0}, {gc1, 0}, {0, 0}, {0, 0}, {0, 0}, {0, 0}}

}

I now get the error as:
Coupling definition in model file for C[V(3),V(3),-V(3),-V(3)] is
incompatible to generic coupling structure. Coupling is not a vector
of length 3

---

Can you please suggest me how to fix this problem? Because somehow the coupling dimension generated by feynrules and feynarts are incomaptible in my case.

I am using following versions of the softwares:
FeynCalc 10 0.1
Feynarts 3 0.12
Feynrules 2.3.49

Thanks in advance,
Disha

[vsht]

Hi,

I think that this question should be better addressed to the developers of FeynRules. This has nothing to do with FeynCalc,
since your code fails already at the stage of generating diagrams with FeynArts.

FeynRules has lots of unexpected pitfalls ...