CalcHEP

Hi!

I have implemented a model in lanhep with no error. Neither lanhep nor calchep detect error.
I also used hermitian check and mass check. every thing is fine. But in the lgrng1.mdl file something looks wrong.
for some 4-particle amplitudes the factor is just a constant, However it must be a function of quartic couplings.
I don't know where this problem comes from.
I can attach the source file if it is necessary.

thanks a lot.

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Alexander Belyaev
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I think its because of a variables like B0000 and etc which lanhep automatically declares.
How could I avoid generating this variables?

 Revision history for this message Alexander Belyaev (alexander.belyaev) said on 2021-02-19: #2

Why do you want to avoid generation of these variables?
And why do you think lagrangian looks wrong?
B0000 etc variables are defined in func.mdl files and aimed to spead up CaclHEP performance by great deal.
What is the preoblem you are facing with?

Hello again and thank you for your helps

In the IDM model for instance, which you have implemented it in the micromegas, in the lgrng1.mdl we can see two different 4-particle amplitude factors that it seems their factors should be the same. But they aren't:

particles factor

z.f z.f ~H+ ~H- -la3
z.f z.f ~H3 ~H3 -1

I think the scattering amplitude of these two are the same. why they are different while ~H+ , ~H- and ~H3 came from a same doublet?

 Revision history for this message Alexander Belyaev (alexander.belyaev) said on 2021-02-21: #4

First of all
z.f z.f ~H3 ~H3 coupling is not -1, it is -B0004 = -la3-la4-la5

Secondly, why do you think that couplings for these interactions should be the same?
Please take a look at the Lagrangian for IDM!

Take a look at one of the papers, e.g. https://arxiv.org/pdf/1612.00511.pdf Eq(2)
You can see from there that couplings for \phi_1\phi_1\phi_2\phi_2
interactions comes from THREE terms:
lam3, lam4, lam5
You can easily derive interactions even without LanHEP for these terms and see that
couplings for
z.f z.f ~H3 ~H3 and z.f z.f ~H+ ~H-
should not be the same

Alexander

dear prof Belyaev
I expanded the lagrangian you have introduced in that paper and found there are repetitious terms for some interactions like z.f z.f ~H3 ~H3.
my question is why we avoid putting such terms repetitiously in our model ?
is it possible to have a same interaction with different couplings ?
I'm sorry because this question doesn't belong to calchep.

sincerely

actually I mean why we don't avoid putting such terms?

 Revision history for this message Alexander Belyaev (alexander.belyaev) said on 2021-02-21: #7

please look carefully at Eq(2) of https://arxiv.org/pdf/1612.00511.pdf

: terms with l3,l4 andl5 are NOT identical!

They form Lorents invariants, but ht econvolution ver SU(2) indices is DIFFERENT!!!

These are different terms and they all must be included, they correspond to THREE different ways of forming
Lorents invariant out of phi1 and phi2 doublets and they ALL must be included

Best Alexander

P.S. I sugest you to close this question

dear prof Bleyaev