Name: V. Shtabovenko Date: 03/03/20-10:33:22 AM Z

Dear Jorge,

you are welcome.

An additional feature of OneLoop not present in TID is the rewriting
of fermion chains into “standard matrix elements”
(arXiv:0709.1075, Section 5), i.e. pieces with chiral projectors GA[6]
and GA[7].
It is quite useful for many EW calculations, especially in B physics.

This is nowadays handled by ToStandardMatrixElement

https://feyncalc.github.io/FeynCalcBook/ref/ToStandardMatrixElement.html

Cheers,
Vladyslav

Am 02.03.20 um 19:32 schrieb Jorge Romão:
> Dear Vladyslav
>
> Thanks for the clarification. Now it does exactly what I need.
>
> Best
>
> Jorge
>
> On 02/03/20 16:26, V. Shtabovenko wrote:
>> UsePaVeBasis enters the stage only if the input contains
>> tensor integrals. In your case there are none, so nothing
>> happens.
>>
>> ToPaVe is applied to any output at the very end, hence, the
>> conversion still occurs.
>>
>> There can be also cases where despite having
>> UsePaVeBasis->True you will still get some scalar integrals
>> as FADs, since those arose through partial fractioning before
>> the actual tensor reduction.
>>
>> Using
>>
>> TID[amp,k1,UsePaVeBasis->True, ToPaVe->True]
>>
>> will ensure that all loop integrals in the output are always written
>> as PaVe functions.
>>
>> Cheers,
>> Vladyslav
>>
>>
>>
>>
>>
>> Am 02.03.20 um 17:00 schrieb Jorge C. Rom�o:
>>> I am moving from OneLoop to TID. However, consider
>>>
>>> amp=FAD[{k1, m1}, {k1 - p1, m2}, {k1 - q1, m3}, q2 + q3]
>>>
>>> which appears in a non irreducible diagram. Now
>>>
>>> TID[amp,k1,ToPaVe->True]//FCE//InputForm =
>>> I*Pi^2*C0[SPD[p1, p1], SPD[q1, q1], SPD[p1, p1] - 2*SPD[p1, q1] +
>>> SPD[q1, q1], m2^2, m1^2, m3^2]*FAD[q2 + q3]
>>>
>>> as it should. However
>>>
>>> TID[amp,k1,UsePaVeBasis->True]//FCE//InputForm
>>> =FAD[q2 + q3]*FAD[{k1, m1}, {k1 - p1, m2}, {k1 - q1, m3}]
>>>
>>> that is does nothing!
>>>
>>> This is a piece inserted in a large code and one does not want to
>>> look at each term and want to use UsePaVeBasis->True to get fewer terms.
>>>
>>> Best
>>>
>>> Jorge
>>>
>>>
>>
>