CalcHEP

QCD corrections in multihiggs models

Asked by Catalina Espinoza

Dear CalHEP team,

In the SM example calchep files the masses of the heavy quarks are defined
as the effective masses, for example:

 Mb |MbEff(Q)

and this masses are then used in the definition of the vertex, for example:

B |b |h | |-EE*Mb/(2*MW*SW) |1

according to the manual, this is done in order to include QCD loop corrections to
the higgs width.

My question pertains the case of a model (non SUSY) with several higgs doublets
all of them with couplings to the fermions,
in which the yukawa couplings no longer are (individually) proportional to the
fermion masses. In such a case, does calchep can compute all the higgses (scalars, pseudo scalars,
charged) widths?

Or else, is it necessary to provide external functions (analogs of MbEff(Q) etc) or
to compute the widths beforehand and feed them to calchep?

Thank you very much in advanced.
Kind regards.

Question information

Language:
English Edit question
Status:
Solved
For:
CalcHEP Edit question
Assignee:
No assignee Edit question
Solved by:
Alexander Pukhov
Solved:
Last query:
Last reply:
Revision history for this message
Best Alexander Pukhov (pukhov) said : 		#1

Effect of running mass appears in result of QCD corrections. It is an
universal feature for all models. So, you can use MbEff in any model.
You have to check that your Higgs model generates b-quark mass Mb. If
Mb is defined as Mb=MbEff(Q) then calculating Higgs width
CalcHEP will substitute Q=HiggsMass automatically. But when you
calculate some cross section, you should take a care about Q.
Sometimes it is not clear which Q we have to substitute.

Best
    Alexander Pukhov

On 07/27/2017 04:19 AM, Catalina Espinoza wrote:
> New question #653752 on CalcHEP:
> https://answers.launchpad.net/calchep/+question/653752
>
> Dear CalHEP team,
>
> In the SM example calchep files the masses of the heavy quarks are defined
> as the effective masses, for example:
>
> Mb |MbEff(Q)
>
> and this masses are then used in the definition of the vertex, for example:
>
> B |b |h | |-EE*Mb/(2*MW*SW) |1
>
> according to the manual, this is done in order to include QCD loop corrections to
> the higgs width.
>
> My question pertains the case of a model (non SUSY) with several higgs doublets
> all of them with couplings to the fermions,
> in which the yukawa couplings no longer are (individually) proportional to the
> fermion masses. In such a case, does calchep can compute all the higgses (scalars, pseudo scalars,
> charged) widths?
>
> Or else, is it necessary to provide external functions (analogs of MbEff(Q) etc) or
> to compute the widths beforehand and feed them to calchep?
>
> Thank you very much in advanced.
> Kind regards.
>
>

Revision history for this message
Catalina Espinoza (macati) said : 		#2

Thank you very much for your answer.

Kind regards.

Revision history for this message
Catalina Espinoza (macati) said : 		#3

Thanks Alexander Pukhov, that solved my question.