Comment 5 for bug 1899608

In my case when trying to generate tthose loops they fail to generate with:

Command "check d d~ > s s~ NP=2 QCD=0 QED=0 [QCD]" interrupted with error:
ValueError : -5 is not in list
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Cheers,

Olivier

> On 16 Oct 2020, at 08:09, Benjamin Fuks <email address hidden> wrote:
>
> Hi Olivier,
>
> Any news here? Is there anything I could do on my side?
>
> Cheers,
>
> Benj
>
> --
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> MadGraph5_aMC@NLO.
> https://bugs.launchpad.net/bugs/1899608
>
> Title:
> Fermion flow issue in the loops
>
> Status in MadGraph5_aMC@NLO:
> New
>
> Bug description:
> Hi everyone,
>
> We are performing some new physics calculations in a model where the
> SM is extended by a squark (and an invisible state that is irrelevant
> for our purpose). The UFO is provided in attachment. The process of
> interest consists in dijet production. I use MG5_aMC 2.6.8 and as a
> process definition, I typed
>
> import model RPVMono_UFO_RG-paper
> set complex_mass_scheme True
> generate p p > j j NP=2 QCD=0 QED=0 [QCD]
> output
>
> In order to solely get QCD corrections to the new physics component, I have modified the madgraph/loop/loop_diagram_generation.py file. I have set the filtering to true (around l388)
> edit_filter_manually = True
> and then included
> loop_pdgs = [abs(x) for x in diag.get_loop_lines_pdgs()]
> is_loop_gluon = (21 in loop_pdgs)
> is_loop_sigma = (9000002 in loop_pdgs)
> if is_loop_sigma and not is_loop_gluon:
> valid_diag=False
> I get the needed diagrams (so that this works).
>
> However, when launching a cross section calculation, I get a pole non-cancellation issue. The weird thing is that poles are fine for the subprocesses
> d dbar to s sbar or s sbar to d dbar
> but not for the subprocess
> dbar d to s sbar
> This is weird as the diagrams are exactly the same. I suspect something problematic with the fermion flow here (as we have clashing arrows diagrams). Any thoughts?
>
> Cheers,
>
> Benj
>
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