Process g g > H and decay chains

Asked by Shubhani Jain on 2020-06-22

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

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2020-06-22
Last query:
2020-06-22
Last reply:
2020-06-22

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

Shubhani Jain (s2697661) said : #2

Hi

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

Regards

Shubhani

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

Shubhani Jain (s2697661) said : #4

Hi

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

Regards
Shubhani

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

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

Shubhani Jain (s2697661) said : #7

Thanks Olivier Mattelaer, that solved my question.

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

You will need to modify the model:
models/hgg_plugin

(and check carefully the new generated model)

Cheers,

Olivier

Shubhani Jain (s2697661) said : #10

Thanks for your help.

Regards
Shubhani