Generation of calchep model files from FeynRules

Asked by Jorge Romao on 2021-04-16

I have a simple 2HDM in FeynRules. I tried to use the function WriteCHOutput. I created the model files and it runs. But I have a problem with the ghost/goldstone expressions. How to generate the equivalent of

A |W+ |W- | |EE
A |W+ |W-.f | |-i*EE*MW
A |W+.f |W- | |i*EE*MW
A |W+.f |W-.f | |-EE
A.C |W+.c |W- | |EE
A.C |W-.c |W+ | |-EE

which I took from the SM model files.

This is probably a beginner's question, but I would appreciate your help

Best

Jorge

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Alexander Belyaev (alexander.belyaev) said :
#1

Dear Jorge,

I am not an expert in Feynrules, but I know how to do this with LanHEP:
 there is an example of how to implement SM in LanHEP, you can find it in
model_src folder under your calchep installation folder.

In particular for higgs doublet in t'Hooft-Feynman gauge take this form (in LanHEP language)

  let shd = { i*'W+.f', (vev(vevh)+h-i*'Z.f')/Sqrt2 }. % scalar Higgs doublet

Talking about ghosts, you can aslo find

let gh= { ('W+.c'+'W-.c')/Sqrt2, i*('W+.c'-'W-.c')/Sqrt2, CW*'Z.c'+SW*'A.c'}.
let Gh= { ('W+.C'+'W-.C')/Sqrt2, i*('W+.C'-'W-.C')/Sqrt2, CW*'Z.C'+SW*'A.C'}.

lterm -g2*eps*deriv*Gh*gh*W.

etc

hope this helps

Best regards,
Sasha

Revision history for this message
Jorge Romao (jorge-romao-y) said :
#2

Dear Sasha

Thanks a lot for your quick reply. I will look then into LanHEP.

Best

Jorge

On 16/04/21 14:41, Alexander Belyaev wrote:
> Your question #696600 on CalcHEP changed:
> https://answers.launchpad.net/calchep/+question/696600
>
> Status: Open => Answered
>
> Alexander Belyaev proposed the following answer:
> Dear Jorge,
>
> I am not an expert in Feynrules, but I know how to do this with LanHEP:
> there is an example of how to implement SM in LanHEP, you can find it in
> model_src folder under your calchep installation folder.
>
> In particular for higgs doublet in t'Hooft-Feynman gauge take this form
> (in LanHEP language)
>
> let shd = { i*'W+.f', (vev(vevh)+h-i*'Z.f')/Sqrt2 }. % scalar
> Higgs doublet
>
> Talking about ghosts, you can aslo find
>
> let gh= { ('W+.c'+'W-.c')/Sqrt2, i*('W+.c'-'W-.c')/Sqrt2, CW*'Z.c'+SW*'A.c'}.
> let Gh= { ('W+.C'+'W-.C')/Sqrt2, i*('W+.C'-'W-.C')/Sqrt2, CW*'Z.C'+SW*'A.C'}.
>
> lterm -g2*eps*deriv*Gh*gh*W.
>
> etc
>
> hope this helps
>
> Best regards,
> Sasha
>

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Revision history for this message
Neil Christensen (neil-christensen-qft) said :
#3

Hi Jorge,

I would look at the FeynRules version of the SM and see how the ghosts and Goldstones are handled in that. Also, please take a look at the manual where we discuss these issues, in particular in relation to the CalcHEP interface. Everything is there.

All the best!
Neil

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