Dear Developer;
When I use TID to do HiggstoGluonGluon oneloop calculation, the result was wrong, and it was same with the calculation that I used Oneloop with oneloopsimplify which was not recommend .
Then I set $LimitTo4=True, the result of OneLoop with OneLoopSimplify was True(agree with my derivation) and the result of TID was still wrong.
I take apart the amplitude into pieces, and I found the one which cause the problem, that is
FeynAmpDenominator[PropagatorDenominator[Momentum[k,D]],PropagatorDenominator[Momentum[k,D]+Momentum[p1,D]],PropagatorDenominator[Momentum[k,D]+Momentum[p1,D]+Momentum[p2,D]]] Pair[LorentzIndex[mu,D],Momentum[k,D]] Pair[LorentzIndex[nu,D],Momentum[k,D]]
in which "k" is loop monentum, and we set all mass to zero, that means p1.p1=0, p2.p2=0.
## four differnt ways
1. $LimitTo4=False (default) , use Oneloop with oneloopsimplify
2. $LimitTo4=False (default) , use TID
#### 3. $LimitTo4=True, use Oneloop with oneloopsimplify
4. $LimitTo4=True, use TID
## we found only the thrid way gave the right answers(agreed with my derivation)
we expect to get the third answers ($LimitTo4=True,use Oneloop with oneloopsimplify) , there should be a term which is not contain B0/C0.
(I \[Pi]^2 Subscript[B, 0](2 p1p2,0,0) (p1p2 g^(munu)-2 p2^mu p1^nu-2 p1^mu p2^nu+3 p1^mu p1^nu-p2^mu p2^nu))/(4 p1p2)+I \[Pi]^2 p1^mu p1^nu Subscript[C, 0](0,0,2 p1p2,0,0,0)+(I \[Pi]^2 (p1p2 g^(munu)-p2^mu p1^nu-p1^mu p2^nu))/(4 p1p2)
TID cannot get the right answer!
code and detail :
https://github.com/FeynCalc/feyncalc/issues/47
https://github.com/Tpengfu/Bug-in-FeynCalc
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