CalcHEP

one-loop matrix element “usrFF”

Asked by Ramtin Taheri

Hi,

I am working on a minimal DM model where DM particles don’t couple to Z bosons at tree level, so, DM, DM -> ZZ is a loop-induced process.

Is there any way to include one-loop matrix element to a CalCHEP model?

I know that we can use “usrFF” to set a K-factor value to approximate effect of loop for a tree-level process. But in my case, there is nothing at tree-level.

Is it possible to modify this function for my model?

Thank you,
Ramtin

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Launchpad Janitor (janitor) said : 		#1

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

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Alexander Belyaev (alexander.belyaev) said : 		#2

Hello, sorry for missing your question.

You can indroduce an effective DM-DM-Z-Z ineractions
and implement your loop function into usrFF

Regards,
Alexander

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