Comment 4 for bug 1732756

Hi,

Did you use the restriction card?

If not this might be (be unlikely) explained by the fact that I’m running 2.6.1 (still in beta).
I do not think that it can explain the difference but maybe.

Cheers,

Olivier

> On Nov 27, 2017, at 16:18, Ilaria Brivio <email address hidden> wrote:
>
> Hi Olivier,
>
> thanks for your answer! Actually I am still having trouble even changing
> the scale choice.
>
> For instance, I am trying with dynamical_scale_choice = 2 and I still
> get an error with the process above if I set to 1 one among the
> parameters
>
> cqd1Abs3333 cqu1Abs3333 cud1Abs3333 cuHAbs3x3
>
> with all the other "c" coefficients to 0. Indeed I get an error with
> other combinations of parameters, but I think the bug is just the same
> for all of them. Also, the same parameters with other processes (e.g.
> with t t~ t t~ in final state) do not give any problem.
>
> I have tried with dynamical_scale_choice = 1 and I get the same. So it
> looks like MG is behaving differently when I run it compared to what you
> get. Is there any log file or similar that can help understanding what
> is going on?
>
> Thank you very much again!
>
> Best,
> Ilaria
>
> --
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> MadGraph5_aMC@NLO.
> https://bugs.launchpad.net/bugs/1732756
>
> Title:
> Error with 4-fermion interactions: failed to reduce to color indices
>
> Status in MadGraph5_aMC@NLO:
> Invalid
>
> Bug description:
> Hi,
>
> I am having problems generating some processes with 4-fermion operators.
> I am using the SMEFTsim UFO attached and I get errors when computing the interference term (the p contains b b~)
>
> p p > t t~ b b~ NP^2==1
>
> when four-quark operators with color singlet contractions are
> included. For instance this happens setting cud13x3x3x3 = 1 while
> leaving the other NP parameters to zero. (there's a restriction file
> in the UFO attached)
>
> The event generation does not crash, but an error appears, referred to
> the channel with gg initial state. I could not find any other flag
> output in the folder, apart from a file named "error", which says just
>
> Error: failed to reduce to color indices: 1 0
>
> I think that the UFO is ok, because the color contractions in the
> vertex (V_184) look ok, and also the same operators work with other
> processes. What can this be then?
>
> Thanks a lot in advance,
> Ilaria
>
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