SMEFTsim param questions

Hi,

The phase-space integration of interference term is something that we have no idea how to do it.
So we have kept the default method for non-interference method. (I would call this a "best effort" attempt)
In simple example this was looking working ok. But on such complex case, I would not be surprise that you face weird behaviour.

Now, I do not know your operator, but even in non interference term, you have sometimes issue with the phase-space integration when some coupling are exactly zero. So I would strongly advise not to do that for interference computation.

Cheers,

Olivier

> On 4 Apr 2019, at 11:27, Rahul Balasubramanian <email address hidden> wrote:
>
> New question #679764 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/679764
>
> Dear experts,
>
> I using the SMEFTsim model to generate interference only events for ggf Higgs decaying to w+w-.
> I use the syntax,
>
> generate g g > h > l+ l- vl vl~ / z a mu+ mu- e+ e- QED==4 NP^2==1
>
> I am encountering an issue regarding the restrict cards. We are primarily interested in a few wilson coefficients
> { c_i } and we would like to generate interfence samples where one wilson coefficient from { c_i }is turned on
> at a time. There are two restrict card scenarios which I try, where I expect the same results but it gives me a
> zero cross-section in one scenario.
>
> Scenario I : Within {c_i} the one that I want to turn on is set to 9.99999e-01,(say cHW) and the rest is set to 1e-99.
> this gives me 2 diagrams and I get a finite non-zero cross-section.
>
> Scenario II : All {c_i} are set to 9.99999e-01 in the restrict card, so this gives me 5 diagrams and then in the
> param_card I turn off {c_i}by setting it 0 -- except cHW. In this scenario I get a 0 cross-section.
> Cross-section : -1.19e-102 +- 1.522e-104 bp
>
> Your insights would be greatly appreciated !
>
> Cheers,
> Rahul
>
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