Name: Ahmad Date: 06/14/19-03:33:34 PM Z

Hello,

I am trying to use FeynHelpers to calculate two loop selfenergy diagrams.I have generated FeynArts amolitude and used FCFAConvert to generate FeynCalc amplitude and then followed the steps described at section 5.4. of FeynHelpers manual: 2-loop self-energies in massless QED.But the following error appears when using FCMultiLoopTID:

During evaluation of In[8]:= $RecursionLimit::reclim2: Recursion depth of 1024 exceeded during evaluation of q1.

During evaluation of In[8]:= $RecursionLimit::reclim2: Recursion depth of 1024 exceeded during evaluation of Refresh[TraditionalFormDump`$UseNewTraditionalForm,None].

During evaluation of In[8]:= $RecursionLimit::reclim2: Recursion depth of 1024 exceeded during evaluation of MakeBoxes[FeynAmpDenominator[PropagatorDenominator[Momentum[q1, D], Mfc], PropagatorDenominator[Momentum[q1, D], Mfc], PropagatorDenominator[Momentum[q2, D], Mfc], PropagatorDenominator[-Momentum[p, D] + Momentum[q1, D], Mfg1], PropagatorDenominator[-Momentum[q1, D] + Momentum[q2, D], MA1]]*Pair[Momentum[p, -4 + D], Momentum[q1, -4 + D]],TraditionalForm].

During evaluation of In[8]:= General::stop: Further output of $RecursionLimit::reclim2 will be suppressed during this calculation.

During evaluation of In[8]:= $RecursionLimit::reclim2: Recursion depth of 1024 exceeded during evaluation of Message[Message::msgl,Hold[{$RecursionLimit::reclim2,FCLoopBasis::fail,$RecursionLimit::reclim2,$RecursionLimit::reclim2,General::stop}]].

During evaluation of In[8]:= $RecursionLimit::reclim2: Recursion depth of 1024 exceeded during evaluation of {$RecursionLimit::reclim2}.

During evaluation of In[8]:= $RecursionLimit::reclim2: Recursion depth of 1024 exceeded during evaluation of {OutputStream[Name: stdout
Unique ID: 1

]}.

During evaluation of In[8]:= General::stop: Further output of $RecursionLimit::reclim2 will be suppressed during this calculation.

During evaluation of In[8]:= FCLoopBasis::fail: Error!
Hold[MakeBoxes[Shallow[“FeynAmpDenominator[PropagatorDenominator[Momentum[q1, D], Mfc], PropagatorDenominator[Momentum[q1, D], Mfc], PropagatorDenominator[Momentum[q2, D], Mfc], PropagatorDenominator[-Momentum[p, D] + Momentum[q1, D], Mfg1], PropagatorDenominator[-Momentum[q1, D] + Momentum[q2, D], MA1]]*Pair[Momentum[p, -4 + D], Momentum[q1, -4 + D]]”, {10, 50}], TraditionalForm]] doesn’t seem to be a single valid loop integral. The integral should be supplied without any prefactors or scalar products that do not depend on the loop momenta. Evaluation aborted.

I will be thankful if you help me with what has caused the error.

Regards.