Name: V. Shtabovenko Date: 05/27/19-07:04:59 PM Z


Hi,

sorry for the late reply. I think that the I gets inserted correctly,
although in the typesetting
is look wrong, cf.

FAD[{p, Sqrt[(Mchi^2 - I*Mchi*\[CapitalGamma]chi)]}]

FAD[{p, Sqrt[(Mchi^2 -
       I*Mchi*\[CapitalGamma]chi)]}] // PropagatorDenominatorExplicit

However, it is still not likely that you can get the correct result with
ComplexConjugate:

If you look at

?ComplexConjugate

there is a clear warning that the denominators may not have imaginary
parts. But this is exactly what you are trying to do. So you would need
some auxiliary function to make sure that the CC of the propagators with
the I’s is taken correctly, otherwise the result is not going to be
consistent.

Cheers,
Vladyslav

Am 15.05.19 um 19:28 schrieb C. Sun:
> Dear Vladyslav and Mailing List Users,
>
> I got stuck by something probably very trivial. In short, I wonder what is the elegant way to include the decay width in an internal propagator. I have tried to implement it as
>
> (*after generating FA diagrams*)
> ruleResonance = {
> Mchi -> Sqrt[(Mchi^2 - I*Mchi*\[CapitalGamma]chi)]
> };
> CreateFeynAmp[diagram] /. M$FACouplings /. ruleResonance
>
> However, after I apply FCFAConvert[], the minus sign is not picked up right. I think that is because all other minus signs have been wrapped as “-“ while the one I manually inserted in front of \Gamma_{\chi} is just a regular minus sign. This causes trouble as later when I do
>
> (amp[0] (ComplexConjugate[amp[0]])) //
> FermionSpinSum[#, ExtraFactor -> 1/2] & //
> DiracSimplify // Simplify// FCE // FeynAmpDenominatorExplicit
>
> all terms with decay width inserted are not simplified.
> Any input would be appreciated.
>
> Best,
> Chen
>