Dear Vladyslav,
I'm trying to calculate a diagram using three different approaches
1) OneLoop
2) TID -> OneLoop
3) OneLoopSimplify -> OneLoop
The first two give a correct result while the last one does not (Mathematica 11.1 and the latest stable version of FeynCalc).
Please note that the difference doesn't seem to be caused by the usual (D-4)/(D-4) terms. I guess that OneLoopSimplify treats chiral projections incorrectly. The example is appended below.
By the way, what is the ``official way" of calculating one-loop integrals, 1,2,3 or maybe none of them?
Best wishes,
Adrian
In[2]:= InfParts := {B0[X__] -> FinB0[X] + 1/eps,
A0[Y_] -> FinA0[Y] + Y/eps};
R = (1 + GA[5])/2;
L = (1 - GA[5])/2;
fad := FeynAmpDenominator;
pd[q_, m_] := PropagatorDenominator[Momentum[q, D], m];
In[9]:= DiagAnum = -I (SPD[k, k] MTD[mu, nu] -
FVD[k, mu] FVD[k, nu]) GAD[
mu].(Fal L + FalCC R).(GSD[k - p] + Mcc L + M R).GAD[
nu].(Fbe L + FbeCC R);
In[10]:= DiagAden = fad[pd[k - p, mF], pd[k, mV], pd[k, 0]];
In[12]:= DiagA = ((4 Pi)^2/(2 Pi)^4) DiagAnum DiagAden ;
(*First way*)
In[16]:= ResA0 = OneLoop[k, DiagA];
In[17]:= ResA0 = ResA0 // DiracSimplify
In[18]:= ResA0 =
ResA0 /. InfParts /. D -> 4 - 2 eps // Series[#, {eps, 0, 0}] & //
Normal
(*Second way*)
In[30]:= ResA = OneLoopSimplify[DiagA, k];
In[20]:= ResA = OneLoop[k, ResA];
In[21]:= ResA = ResA // DiracSimplify;
In[22]:= ResA =
ResA /. InfParts /. D -> 4 - 2 eps // Series[#, {eps, 0, 0}] & //
Normal
(*Third way*)
In[23]:= ResA1 = TID[DiagA, k];
In[24]:= ResA1 = OneLoop[k, ResA1];
In[25]:= ResA1 = ResA1 // DiracSimplify;
In[26]:= ResA1 =
ResA1 /. InfParts /. D -> 4 - 2 eps // Series[#, {eps, 0, 0}] & //
Normal
(*Comparison*)
In[27]:= ResA1 - ResA0 // Simplify
Out[27]= 0
In[28]:= Limit[eps ( ResA1 - ResA), eps -> 0] // Simplify
Out[28]= -(3/
2) (FalCC M - Fal Mcc) (Fbe (-1 + DiracGamma[5]) +
FbeCC (1 + DiracGamma[5]))
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