p p > w+ w+ p p specific diagrams

Hi Andrew,

Nothing automatic, you need to do it by hand.

They are two typical way
1) modify the model and add an order like QED/QCD which allow you to select those diagram.
2) generate all the diagram and then edit the various matrix.f by hand to remove all the diagram that you don’t want to include.

Obviously you are fully responsible of the physical meaning of your process with such modification.

Cheers,

Olivier
On May 14, 2014, at 7:51 PM, Andrew Levin <email address hidden> wrote:

> New question #248683 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/248683
>
> Hi,
>
> I would like to generate
>
> p p > w+ w+ p p
>
> but only some specific diagrams:
>
> 1) the diagram with a w+w+w+w+ vertex
>
> 2) the diagram where the w+w+ are scattered through a higgs boson
>
> Is it possible in madgraph?
>
> Thanks.
>
> Andrew
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

So, if I want to select this vertex

V_55 = Vertex(name = 'V_55',
              particles = [ P.W__minus__, P.W__minus__, P.W__plus__, P.W__plus__ ],
              color = [ '1' ],
              lorentz = [ L.VVVV2 ],
              couplings = {(0,0):C.GC_35})

is it right that I should change

GC_35 = Coupling(name = 'GC_35',
                 value = '-((ee**2*complex(0,1))/sw**2)',
                 order = {'QED':2})

to

GC_35 = Coupling(name = 'GC_35',
                 value = '-((ee**2*complex(0,1))/sw**2)',
                 order = {'QED/QCD':2})

and then do

generate p p > w+ w+ p p QED=2 QED/QCD=2 QCD=99, w+ > l+ vl

?

By the way, why are there only two coupling constants in madgraph: QED and QCD. Should there also be EWK?

Andrew

Hi,

Yes,

But in top of that you need to define this new coupling in coupling_order.py

Cheers,

Olivier

> By the way, why are there only two coupling constants in madgraph: QED
> and QCD. Should there also be EWK?

Typically you don’t want to split those two contribution since they are of the same order.
In top of that, the photon and the Z are mixed state so I don’t think it really makes sense.

On May 17, 2014, at 9:26 PM, Andrew Levin <email address hidden> wrote:

> Question #248683 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/248683
>
> Andrew Levin posted a new comment:
> So, if I want to select this vertex
>
> V_55 = Vertex(name = 'V_55',
> particles = [ P.W__minus__, P.W__minus__, P.W__plus__, P.W__plus__ ],
> color = [ '1' ],
> lorentz = [ L.VVVV2 ],
> couplings = {(0,0):C.GC_35})
>
> is it right that I should change
>
> GC_35 = Coupling(name = 'GC_35',
> value = '-((ee**2*complex(0,1))/sw**2)',
> order = {'QED':2})
>
> to
>
> GC_35 = Coupling(name = 'GC_35',
> value = '-((ee**2*complex(0,1))/sw**2)',
> order = {'QED/QCD':2})
>
> and then do
>
> generate p p > w+ w+ p p QED=2 QED/QCD=2 QCD=99, w+ > l+ vl
>
> ?
>
> By the way, why are there only two coupling constants in madgraph: QED
> and QCD. Should there also be EWK?
>
> Andrew
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Does this definition in coupling_order.py make sense

QCD = CouplingOrder(name = 'QCD',
                    expansion_order = 99,
                    hierarchy = 1)

QED = CouplingOrder(name = 'QED',
                    expansion_order = 99,
                    hierarchy = 2)

EWK1 = CouplingOrder(name = 'EWK1',
                    expansion_order = 99,
                    hierarchy = 2)

?

I am not sure if expansion_order = 99 and hierarchy = 2 make sense for this new coupling order (which is used for some vertices that had the QED order before).

Yes it is fine.

Cheers,

Olivier
On May 21, 2014, at 10:11 PM, Andrew Levin <email address hidden> wrote:

> Question #248683 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/248683
>
> Andrew Levin posted a new comment:
> Does this definition in coupling_order.py make sense
>
> QCD = CouplingOrder(name = 'QCD',
> expansion_order = 99,
> hierarchy = 1)
>
> QED = CouplingOrder(name = 'QED',
> expansion_order = 99,
> hierarchy = 2)
>
> EWK1 = CouplingOrder(name = 'EWK1',
> expansion_order = 99,
> hierarchy = 2)
>
> ?
>
> I am not sure if expansion_order = 99 and hierarchy = 2 make sense for
> this new coupling order (which is used for some vertices that had the
> QED order before).
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.