Decay of neutral particle

Asked by Maksym Ovchynnikov on 2019-07-01

I am simulating a process with

p p > h w+, w+ > e+ ve, (h > sp sp, (sp > mu+ mu-))

where sp is new real scalar particle.

I expect to see a diagram at which only one sp decays, however, it shows that two scalars decay. How to restrict MadGraph to decay only one of the scalars?

Or, at least, how to distinguish between mu- mu+ pair of one scalar and another one? Namely, if I would like to select the mu+ from the decay products, I need to adjust to it the mu-, and naively there is an ambiguity...

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2019-07-01
Last query:
2019-07-01
Last reply:
2019-07-01

Hi,

Even if this is technically possible, The short answer is you can't.
The problem is that if you do it you will mess up with the symmetry factor and lead to incorrect result.

> Or, at least, how to distinguish between mu- mu+ pair of one scalar and another one? Namely, if I would like to select the mu+ from the decay products, I need to adjust to it the mu-, and naively there is an ambiguity...

In the lhef file you have the "parent" information. Since your scalar are consider as onshell due to your syntax, the sp lines are included within the lhef file and you should have that information.

The parton-shower program has the same type of information as well.

Cheers,

Olivier

Maksym Ovchynnikov (name-xxx) said : #2

Thanks Olivier Mattelaer, that solved my question.