How to generate interference-term-only for VBS/QCD with MG_aMC@NLO?

Dear Shu,

> Is it true that only interference term will be generated if we do using the syntax as:
> “generate p p > w+ a j j QCD^2==0"

The syntax indeed exists:

The ^2 means that you apply coupling restriction at the level of the matrix element square.
The “==“ means that you ask exactly that number of coupling.

so QCD^2==0, means that you ask exactly 0 QCD coupling at the matrix element square.
This is therefore equivalent to do
generate p p > w+ a j j QCD=0
which is your VBS sample and not what you want.

I guess that the syntax that you look for is
generate p p > w+ a j j QCD^2==2

Cheers,

Olivier

On 03 Sep 2015, at 11:26, newid <email address hidden> wrote:

> New question #271045 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/271045
>
> Dear MadGraph authors and experts,
>
> May I ask a question how to generate the interference term only using MadGraph_aMC@NLO 5.2 for VBS/QCD interference?
> e.g. if we are talking about VBS of Wgamma+2jets, it should be:
> for QCD: p p > w+ a j j QED=2
> for VBS: p p > w+ a j j QCD=0
> for INTERFERENCE: p p > w+ a j j QCD=2
> and to get the interference term only, we need to do subtraction as : (INTERFERENCE - QCD - VBS)
>
> I have newly learnt that there is a new way to directly generate the interference term only in this case.
> Is it true that only interference term will be generated if we do using the syntax as:
> "generate p p > w+ a j j QCD^2==0"
>
> Many thanks.
>
> best,
> Shu
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.