MadGraph5_aMC@NLO

mass shuould be real number

Asked by zhangshuli

when i use type ii seesaw model.
i change the mass of DPP to 1400,but the command "generate events run01 "interrupted with error.
Exception： mass should be real number ：particle 62 chi has mass：1777.0661204548699j
May i ask how the mass of 62 chi should be modified？
what does j after 1777 mean？
please have time to reply me
thankyou very much

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

They are many type II model available online, so I will not be able to answer your first question.
The only way to answer such question is to read how the mass of that particle is computed. And such definition should be part of the parameters.py file.

The question about "j" is more simple, this is the python representation of the pure imaginary complex number.
This is why we crash here, because we do not allow particle to have an imaginary complex value (but if you use the complex mass-scheme).

This likely means that your mass is computed via a squareroot and that your benchmark makes that square-root to be negative.

Cheers,

Olivier

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zhangshuli (slzhang) said : 		#2

Hello,
Thank you for your prompt response.
It is very useful.
Best wishes!