Generation of ssWWjj strong production at NLO

Hi,

> But I’m having trouble with the strong production processes:
> generate p p > w+ w+ j j QED=4 QCD=2 @1 [QCD]
> add process p p > w- w- j j QED=4 QCD=2 @2 [QCD]

This is not the strong production but a mix between VBF and QCD production.
The strong production syntax should be
> generate p p > w+ w+ j j QED=2 QCD=2 @1 [QCD]
> add process p p > w- w- j j QED=2 QCD=2 @2 [QCD]

> Error in computation of bpower:
> not an integer 1.7916701512582685

This is a clear sign that you have mix expansion issue already at born level.
For such kind of computation we can only do fix order computation (and with MadGraph5_aMC@NLO version 3 which is currently in beta --and 3.0.2 will be release in beta soon--)
please take a look at 1804.10017 <https://arxiv.org/abs/1804.10017>

> Also, would like to confirm that I am doing the right thing for the interference term at NLO by using
> generate p p > w+ w+ j j QCD^2==2 [QCD]
> add process p p > w- w- j j QCD^2==2 [QCD]

No, such kind of computation are only possible with version 3 (and no event generation)
Note that pure interference are NOT advise since they are typically plegde with issue on the phase-space integrator side.

Cheers,

Olivier

> On 11 May 2020, at 10:49, Karolos Potamianos <email address hidden> wrote:
>
> New question #690621 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/690621
>
> Hello,
>
> I reach out to ask some advice on the production of two same-sign WW bosons in association with two jets (ssWWjj) with MadGraph (2.6.7).
>
> I am already successfully producing samples at LO. At NLO, I manage to produce
> generate p p > l+ vl l+ vl j j QCD=0 [QCD]
> add process p p > l- vl~ l- vl~ j j QCD=0 [QCD]
>
> But I’m having trouble with the strong production processes:
> generate p p > w+ w+ j j QED=4 QCD=2 @1 [QCD]
> add process p p > w- w- j j QED=4 QCD=2 @2 [QCD]
>
> I’m using
> set complex_mass_scheme
> import model loop_qcd_qed_sm_Gmu-atlas
>
> And MadSpin for the decay.
>
> But I get the following error when making my grid pack:
>
> aMCatNLOError : An error occurred during the collection of results.
> Please check the .log files inside the directories which failed:
>
> And all the log files contain lines like this:
>
> Error in computation of bpower:
> not an integer 1.7916701512582685
>
> This looks very similar to this: https://answers.launchpad.net/mg5amcnlo/+question/632738 ; I saw that there – for a different case – Olivier pointed out that “Even in the case of the standard model, we cannot compute such process since some diagram are actually some QED correction to a QCD process.” Assuming the issue is the same, could you point me to ways how to not generate these problematic processes (or even if it would be OK to do so, i.e. that their contribution is small enough) ?
>
>
> Also, would like to confirm that I am doing the right thing for the interference term at NLO by using
> generate p p > w+ w+ j j QCD^2==2 [QCD]
> add process p p > w- w- j j QCD^2==2 [QCD]
>
> Thanks,
> Karolos
>
>
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