MadGraph5_aMC@NLO

helicity projection in madgraph5

Asked by Abhaya Kumar Swain

Hi there,
    I was trying to build a toy model having only left handed top quark. By left handed I mean helicity projection states.
As we know the helicity projection operator is (1/2) (1+- gamma5*gamma_mu*S^mu) , with S^mu = (0 , P_t/m_t ).
Where "P_t" is a unit vector in top quark momentum direction.

Can any body tell me how to implement this in matrix element level in MG5.

Thanks in advance.

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Why not using FeynRules for this?

Otherwise, you need to go trough each interaction with a top and add you projector for all of those.
(but keeping intact the lorentz structure for the other one)

The following paper contains all the details that you need:
arXiv:1108.2040
and this one explains how this information is handle:
arXiv:1108.2041

Cheers,

Olivier

On Jun 10, 2014, at 8:02 AM, Abhaya Kumar Swain <email address hidden> wrote:

> New question #250019 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/250019
>
> Hi there,
> I was trying to build a toy model having only left handed top quark. By left handed I mean helicity projection states.
> As we know the helicity projection operator is (1/2) (1+- gamma5*gamma_mu*S^mu) , with S^mu = (0 , P_t/m_t ).
> Where "P_t" is a unit vector in top quark momentum direction.
>
> Can any body tell me how to implement this in matrix element level in MG5.
>
> Thanks in advance.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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