SMEFT@NLO decay

For the Higgs decay from a loop-induced process, the only options is (within our framework)
madspin with set spinmode=none.

But indeed, this will apply the same BR to all weights and we do not have create any wrapper for such situation.

Knowing that set spinmode=none is extremelly basic since it does
1) run standard madevent for 1> n process
2) merge the two lhef file (production one and decay one) into a single one.

What I would suggest is to
1) run by hand madevent + re-weighting for the 1> N process
2) merge the two lhef file (either with the parser of your choice or with the one that we have built within MG5aMC: madgraph/various/lhe_parser.py) to merge the file and then tweak the writting of the weight such that the BR are correctly handle.

Cheers,

Olivier

Thank you, I'll try this way.

Cheers,

Massimiliano

Hi, I ask another question under this thread since it is something that I saw while trying out the suggestion.
I'm now trying to simulate separately the decay h > b b~. I proceed like follows:

import model SMEFTatNLO-LO

generate h > b b~ NP=2 QCD=2 QED=1

The reason why I do this is because if I type

display interactions h b b~

I see also

Interactions 576 : b~ b h has the following property:
{
    'id': 576,
    'particles': [-5,5,25],
    'color': [1 T(1,0)],
    'lorentz': ['FFS33'],
    'couplings': {(0, 0): 'R2GC_666_1842'},
    'orders': {'NP': 2, 'QED': 1, 'QCD': 2},
    'loop_particles': [[5, 21]],
    'type': 'R2',
    'perturbation_type': None
}

However, when trying the command above, I get

INFO: Trying process: h > b b~ NP<=2 QCD<=2 QED<=1 @1
Command "generate h > b b~ NP=2 QCD=2 QED=1" interrupted with error:
NoDiagramException : No amplitudes generated from process Process: h > b b~ NP=2 QCD=2 QED=1 @1. Please enter a valid process

Am I doing something wrong?

Thanks,

Massimiliano

The type "R2" means that this is a vertex encoding the finite part of a loop diagram where the loop is a triangle with external leg one higgs , one b and one b~. So indeed this is not a valid interaction for a Higgs decaying to b b~ at tree level.

Cheers,

Olivier

Thank you for your answer. If I may ask, what is then the correct way to simulate this decay with SMEFTatNLO?

Thanks,

Massimiliano