Fewer events generated than asked for in w+w+jj process @ 100TeV

Hi Kylin,

The phase-space parametrization use for the integration of the matrix-element is know to be not very efficient in case of VBF process.
We already have efficiency issue sometimes for LHC run and I will not expect that increasing the energy to help on that matter.

Cheers,

Olivier

On Mar 28, 2014, at 4:46 AM, Kylin Qu <email address hidden> wrote:

> New question #246169 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/246169
>
> Hi,
>
> I am trying to generate events for the process " p p > w+ w+ j j QED=4 QCD=99 ". It worked pretty well at center of mass energy 8TeV and 14TeV, but failed to give enough events as required (e.g., 10000 = nevents) at 100TeV. I have set cuts like
>
> 20 = ptj ! minimum pt for the jets
> 5 = etaj ! max rap for the jets
> 0.4 = drjj ! min distance between jets
>
> and generated events without matching. The PDF set is cteq6l1.
>
> Since this process involves too much diagrams I have also tested some simplified process like " u d~ > w+ > w+ w+ d u~ ". Still gives fewer events. I also tried PDF set cteq6_m and the problem remained.
>
> Besides, for 100TeV, I also generated other process like " p p > w+ z j j QED=4 QCD=99 " and it seems fine, giving enough events as required.
>
> Thanks.
> Kylin
>
> --
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Hi Olivier,

Thanks for your reply. So I am wondering if the cross section as well as the events generated still "physical" to be used in analysis? I mean, does it make sense if I just simply keep generating more events? And do you have any plans to fix this issue?

Best,
Kylin

Hi Kylin,

Thanks for your reply. So I am wondering if the cross section as well as the events generated still "physical" to be used in analysis? I mean, does it make sense if I just simply keep generating more events?

Yes this makes a lot of sense. You just expect that statistical fluctuation are a bit larger than for other sample.

And do you have any plans to fix this issue?

This is in discussion, but clearly not in any short term.

Cheers,

Olivier

Hi Olivier,

Just wanted to add that I'm running into the same issue at 100 TeV with (including deltaeta=4):
generate p p > j j z QCD=2 QED=1, z > vl vl~
add process p p > j j j z QCD=3 QED=1, z > vl vl~

Why would this be worse at 100 TeV than at 8 or 14 TeV?

Thanks,
- Matthew