Process g g > H and decay chains

Asked by Shubhani Jain

Hi

We are trying to do MG5 run for process g g >H. It can be done with 2HDM_NLO model but it doesn't allow decay chain for example
g g > h2, (h2 > h1 h1, (h1 > b b~), (h1 > b b~)). Is it possible to do 2HDM + ggH interaction for the initial heavy Higgs production in Madgraph right now or do we need to construct our own model and then do MG5 run?

Regards
Shubhani

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Olivier Mattelaer
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Olivier Mattelaer (olivier-mattelaer) said :
#1

Hi,

loop induced processes does not allow decay-chain syntax.
For the Higgs case, the method advised in the loop induced paper is still our suggestion:
use Madspin in "spinmode=none" mode (no spin-correlation between production and decay and no offshell effect)

Note that for the Higgs case, you can also shrink the loop (as long as mh<2*mt) and use an effective operator, which then allow you to use the decay chain approach.

Cheers,

Olivier

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Shubhani Jain (s2697661) said :
#2

Hi

Would it be easier to implement our own model 2HDM+ ggH in Madgraph?

Regards

Shubhani

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Olivier Mattelaer (olivier-mattelaer) said :
#3

Using MadSpin is certainly simpler than generating a model.
Now simulation of loop-induced is more cpu intensive than a tree-level computation.

In any case the first question is which precision do you want to have (loop-induced is more precise since it also includes the b loop contribution and is valid not only for single H production but for H plus jets production as well)

Cheers,

Olivier

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Shubhani Jain (s2697661) said :
#4

Hi

Just one more question: do 2HDM_NLO model has g-g-H effective vertex implemented?

Regards
Shubhani

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Shubhani Jain (s2697661) said :
#5

Hi

Using madspin gives me an error:

Command "generate_events run_01" interrupted with error:
NoDiagramException : No amplitudes generated from process Process: g g > h2 WEIGHTED=4 @1. Please enter a valid process

Can you explain why is that?

Regards
Shubhani

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Best Olivier Mattelaer (olivier-mattelaer) said :
#6

Hi,

> do 2HDM_NLO model has g-g-H effective vertex implemented?

I do not know that model (they are so many model, I do not know most of them)
But your next message indicates that No, this is not implemented.

> Using madspin gives me an error:
This is not a madspin error.
With this model , you should be able to run the following script:

import model 2HDM_NLO
generate g g > h2 [QCD]
output
launch
madspin=none
decay h2 > h1 h1, h1 > b b~

If you want to use the ggh effective vertex and if the PDG code of h2 is 25, then you can do the following

import model 2HDM_NLO
add model hgg_plugin
generate g g > h2, (h2 > h1 h1, h1 > b b~)

Cheers,

Olivier

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Shubhani Jain (s2697661) said :
#7

Thanks Olivier Mattelaer, that solved my question.

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Shubhani Jain (s2697661) said :
#8

Hi

Just one more question is it possible to edit the particle pdg’s etc in hgg_plugin so that they match the 2HDM_NLO ones?

Regards
Shubhani

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Olivier Mattelaer (olivier-mattelaer) said :
#9

You will need to modify the model:
models/hgg_plugin

(and check carefully the new generated model)

Cheers,

Olivier

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Shubhani Jain (s2697661) said :
#10

Thanks for your help.

Regards
Shubhani