ggttbar effective vertex

Do you mean F_munu F_munu t t_bar?
Best
    Alexander Pukhov

On 06/29/2016 08:43 AM, starterism wrote:
> New question #295756 on CalcHEP:
> https://answers.launchpad.net/calchep/+question/295756
>
> My BSM model can generate a four-point ggttbar vertex. it seems calchep can't calculate this kind of vertex ( just like 4-feimi vertex?)
> What should I do to realize the calculation of this kind of vertex?
>
> (I know I should use a auxiliary field to deal with 4-feimi operator.)
>

no, I mean F_munu t t_bar. (There are f^abc g^b_mu g^c_nu term in F_munu, and this term generate the 4-point vertex )

Best

Xiaohu Wang

You can find the complete dimension 6 operate O_tG at page 11 of arXiv:1008.3869

This operate can generate the vertex I've mentioned above. It seems that Calchep can't deal with this kind of vertex.

Best

Xiaohu Wang

Show me, please, a vertex which can not be realized in CalCHEP.
Usually LanHEP solves the problem of vertex generation. If not, I
can show you how it can be done by hand.
But I have not time to write full list of operators presented in some
paper.
In general auxillary fields with point-like propagators are used to
generate complex vertex.
Best
    Alexander Pukhov

On 06/30/2016 08:12 AM, starterism wrote:
> Question #295756 on CalcHEP changed:
> https://answers.launchpad.net/calchep/+question/295756
>
> starterism posted a new comment:
> You can find the complete dimension 6 operate O_tG at page 11 of
> arXiv:1008.3869
>
> This operate can generate the vertex I've mentioned above. It seems that
> Calchep can't deal with this kind of vertex.
>
> Best
>
> Xiaohu Wang
>

The vertex is
        t tbar sigma^{munu} lambda^A f^{ABC} G^B_mu G^C_nu

It can be generated but uncalculated.

Best

Xiaohu Wang

You can write in LanHEP model file

parameter Lambd=1.

lterm
Lambd*i*T*gamma^mu*gamma^nu*lambda^a*t*(deriv^mu*G^nu^a-deriv^nu*G^mu^a+i*GG*f_SU3^a^b^c*G^mu^b*G^nu^c).

Then LanHEP generates T*t*G vertex

T |t |G | |Lambd |G(p3)*G(m3)-G(m3)*G(p3)

One auxiliary vector particle will be added to particle list:

GGTt |~00|~01| |2 |Maux|0 |8 |!* |

GGTt.t is a special object with 2 indexes whose propagator is a
product of 2/**/**Kronecker deltas./*
*/It allows to construct the TtGG vertex

G |G |~01.t| |1 |m1.m3*m2.M3-m1.M3*m2.m3
T |t |~00.t| |GG*Lambd |G(M3)*G(m3)

The exclamation mark in GGTt specification means that each component
of GGTt is self-conjugated. So

T |t |~01.t
and
G |G |~00.t

are not requested by CalcHEP

Best
    Alexander Pukhov

On 06/29/2016 03:17 PM, starterism wrote:
> Question #295756 on CalcHEP changed:
> https://answers.launchpad.net/calchep/+question/295756
>
> Status: Answered => Open
>
> starterism is still having a problem:
> no, I mean F_munu t t_bar. (There are f^abc g^b_mu g^c_nu term in
> F_munu, and this term generate the 4-point vertex )
>
> Best
>
> Xiaohu Wang
>