changing model parameters

Asked by Nikhil Bachhawat


I was trying to change the triple Higgs self-coupling value in SM. I know that there are .mdl files in the share/models folder. In that the SM.mdl file seems to have some variables that would be used to calculate the triple higgs coupling. Also there is a F90 file with the gh3 variable in it in the src/models folder.

I wanted to know if changing variable values in these files is the way to change the coupling or is there a better way? I do not want to affect any other properties of the SM model and so directly changing gh3 would be ideal I think. But whizard does not allow access to that variable from the interactive session.


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Juergen Reuter
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Best Juergen Reuter (j.r.reuter) said :

Hi Nikhil,
of course you can edit the file src/models/parameters.SM.f90 and then recompile. However, this is not
really the intended way. The intended way is that you use the model SM_ac instead of SM and then you
can directly set the parameter fac_gh3 which serves as a kappa parameter for the triple Higgs coupling.
You also have to set ka = 0 and kz = 0 I think. Otherwise there are anomalous triple gauge couplings, please
check. The third possibility is that you take a UFO model with a modified triple Higgs coupling.

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Nikhil Bachhawat (nikhilb1997) said :

Thanks Juergen Reuter, that solved my question.