How to consider the coupling of different intermediate state processes

Asked by zxy

Now I have considered two processes. Except for the propagator in the middle, the initial state particles and the final state particles are exactly the same. My production process is as follows:

define n = n1 n2

generate e- e+ > n ve~ , ( n > w+ e-, w+ > c s~)

Where n is the heavy neutrino, which is the particle of the new physical model defined by feynrules.

However, in the process of generating with this statement, the image madgrah corresponding to different n does not interfere. I want the two processes to interfere. What should I do?

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MadGraph5_aMC@NLO Edit question
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Olivier Mattelaer
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Olivier Mattelaer (olivier-mattelaer) said :
#1

Yes this make sense since you use the Narrow-width approximation and in that approximation it does not make sense to have the interference term.

So I would advice to use
generate e- e+ > ve~ w+ e-, w+ > c s~
or potentially this syntax:
generate e- e+ > n1 | n2 > ve~ w+ e-, w+ > c s~

Cheers,

Olivier

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zxy (sduzxy) said :
#2

Thank you for your answer.
In the two solutions you mentioned, they do not use the Narrow-width approximation of n.
What can we do to consider the Narrow-width approximation of n, but also make different processes interfere?

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Best Olivier Mattelaer (olivier-mattelaer) said :
#3

This is not possible with our code.
To be honest, I do not see a case where the narrow width approximation can be valid if the interference is relevant.

Cheers,

Olivier

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zxy (sduzxy) said :
#4

Thanks Olivier Mattelaer, that solved my question.