Name: Duarte (email_not_shown)
Date: 01/18/18-09:55:06 AM Z


Sure;
I start by making some definitions:

(* ----------- Definitions ----------- *)
Deno[k_,m_]:=FeynAmpDenominator[PropagatorDenominator[k,m]]
dm[mu_]:=DiracMatrix[mu,Dimension->d]
dm[5]:=DiracMatrix[5]
ds[p_]:=DiracSlash[p,Dimension->d]
ds2[p_]:=DiracGamma[Momentum[p]]
fprop[p_,m_]:=ds[p] + m
fv[p_,mu_]:=FourVector[p,mu,Dimension->d]
po2[p_]:=Pair[Momentum[p], Momentum[p]]
mt[mu_,nu_]:=MetricTensor[mu,nu,Dimension->d]

Then, I write some Feynman rules:

(* ----------- Feynman Rules ----------- *)
GaugeP[k_,m_,mu_,nu_]:= (-I) Deno[k,m] mt[mu,nu]
FermiP[p_,m_]:= I fprop[p,m] Deno[p,m]
ffZ[mu_]:= (-I) g/cw dm[mu] (gv - ga dm[5])
ffW[mu_]:= (-I) g/Sqrt[2] dm[mu] (1-dm[5])/2

Finally, the amplitudes:

(* ----------- Amplitudes ----------- *)
ampF1:= Contract[GaugeP[k,MZ,a,b] . ffZ[b] . FermiP[p+k,mf] . ffZ[a]]
ampW1:= (-1) Tr[FermiP[k,mf] . ffW[nu] . FermiP[k+p,mfp] . ffW[mu]]

The first problem I mentioned shows up when I try to compute
OneLoop[k,ampF1] (this means I was incorrect; the problem is not
in the Contract itself, but in the the attempt to use OneLoop to
the contracted structure). Here's what I get:

   In[21]:= OneLoop[k, ampF1]

   During evaluation of In[21]:= DiracTrick::failmsg: Error! DiracTrick
   has encountered a fatal problem and must abort the computation. The
   problem reads: Incorrect combination of dimensions and g^5 scheme!

   Out[21]= $Aborted

The second problem shows up when I try to compute ampW1 (it means it's
a trace problem, not a loop problem). Here's what I get:

   In[22]:= ampW1

   During evaluation of In[22]:= DiracTrace::failmsg: Error! DiracTrace
   has encountered a fatal problem and must abort the computation. The
   problem reads: Irregular trace structure in

   During evaluation of In[22]:= (g^2
   FeynCalc`DiracTrace`Private`dsHead((\[Gamma]\[CenterDot]k+mf).(1-
   Overscript[\[Gamma], _]^5)) FeynCalc`DiracTrace`Private`dsHead(\
   [Gamma]^mu \[Gamma]^nu.(\[Gamma]\[CenterDot](k+p)+mfp).(1-
   Overscript[\[Gamma], _]^5)))/(8 (k^2-mf^2) ((k+p)^2-mfp^2))

   Out[22]= $Aborted

Thanks again,
Duarte



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