Dear Paulina,
can you provide the squared amplitude (or a piece thereof)
that generates this message? Essentially a minimal working example
to understand what happens.
$AL($188) is just a dummy index that is automatically introduced
when squaring an amplitude to avoid violating Einstein's summing
convention. That should not be an issue.
Cheers,
Vladyslav
Am 16.07.20 um 22:45 schrieb Paulina Knees:
> Dear author,
> I'm calculating the decay width of a massive neutrino decaying to three SM neutrinos through a Z boson. But when I want to calculate the squared amplitude (including fermion spin sum), I get the following error message:
>
> "Error! DiracTrace has encountered a fatal problem and must abort the computation. The problem reads: Trace still
> contains chiral projectors.
>
> I realised that the product of the amplitude and its conjugate contains terms with "gamma^$AL($188)" and "gamma^$AL($189)", and I don't really know what it is. Besides, the amplitude I get with FeynArts seems to be right.
>
> Thank you very much for your time,
> Bests,
>
> Paulina (pknees@df.uba.ar)
>
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