reweight crashes on loop-induced processes

[Samuel Homiller]

Dear MG5 team,

I am attempting to use the reweighting feature on a loop-induced process (Higgs-pair production via gluon fusion). For a simple example, I tried

import model loop_sm
generate g g > h h QED^2<=4 QCD^2<=4 [QCD]

and in the reweight card, following the example in http://feynrules.irmp.ucl.ac.be/attachment/wiki/SMEFTatNLO/tree-loop_instructions.txt, I tried:

change process g g > h h QED^2<=4 QCD^2<=4 [virt=QCD]
launch
set yukawa 6 120

(I also tried without the change process line).
This gives an AttributeError "'int' object has no attribute 'decode'. I attached the debug.log file below, in case this is useful.

[Olivier Mattelaer (olivier-mattelaer)]

Hi,

This sounds an error introduces by the migration to python3.
So I would suggest checking the Long Term Stable version (2.9.x) of MG5aMC which can still run python2.

I will see what I can do as soon as possible to fix the issue.