Delphes and MG5_aMC@NLO

Hi Felix,

> 1. Is there a good manual or tutorial that explains the new features of MG5_amc@NLO?

We are writing it right now.

> 2. I would like to generate BG events (including a detector simulation) using MG5_amc@NLO. When using MG5_amc@NLO, I have not seen an option that automatically runs Delphes or Pythia after the event generation. Is there a possibility to run Pythia/Delphes automatically or do I have to run Delphes afterwards using the output file.

You can already run the shower (and you have the choice with many of them (i.e. Pythia 6/8 and herwig/herwig++)
Delphes is not yet possible to run automatically but this should be include soon.

> 3. Is there any overlap/double counting if i use
> generate p p > t t~ [QCD]
> add process p p > t t~ j [QCD]
> add process p p > t t~ j j [QCD] ?
> Is it even necessary to include the processes with additional jets or are they included in the NLO corrections?

Yes they are double counting, they can be remove with the FxFx merging: (see http://amcatnlo.cern.ch/FxFx_merging.htm for more details)
and here the official paper for the method: http://arxiv.org/abs/1209.6215
Otherwise the generation
> generate p p > t t~ [QCD]
contains 0 and 1jet event

> 4. I have seen that the run_card has a different format than the usual MG5 run_card. Are there any additional cuts applied somewhere (like Delta_R between leptons, jets) that are not shown in the run_card? I would like to compare cross sections to theoretical cross sections and additional cuts would change my generated result.

You can implement the cuts directly by modifying the file SubProcesses/cuts.f if you need more cuts.

> 5. Is it possible to generate for example an fully leptonic ttbar decay at NLO. Something like
> generate p p > t t~ , ( t > b w+ , w+ > l+ vl ) , ( t~ > b~ w- , w- > l- vl~ ) ?

MadSpin (http://arxiv.org/abs/arXiv:1212.3460) can handle the decay of NLO process with full spin correlation and finite width effect (but the decay is done at LO precision)

What you should do in that case, is doing the following
generate p p > t t~ [QCD]
output
launch
madspin=ON

Then edit the MadSpin card to specify the decay that you want.
You have even more details on MadSpin at the following page: https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/MadSpin

Cheers,

Olivier

On Mar 4, 2014, at 2:16 AM, Felix Kling <email address hidden> wrote:

> New question #244938 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/244938
>
> Hi,
>
> i have a few questions about MG5_amc@NLO:
>
> 1. Is there a good manual or tutorial that explains the new features of MG5_amc@NLO?
>
> 2. I would like to generate BG events (including a detector simulation) using MG5_amc@NLO. When using MG5_amc@NLO, I have not seen an option that automatically runs Delphes or Pythia after the event generation. Is there a possibility to run Pythia/Delphes automatically or do I have to run Delphes afterwards using the output file.
>
> 3. Is there any overlap/double counting if i use
> generate p p > t t~ [QCD]
> add process p p > t t~ j [QCD]
> add process p p > t t~ j j [QCD] ?
> Is it even necessary to include the processes with additional jets or are they included in the NLO corrections?
>
> 4. I have seen that the run_card has a different format than the usual MG5 run_card. Are there any additional cuts applied somewhere (like Delta_R between leptons, jets) that are not shown in the run_card? I would like to compare cross sections to theoretical cross sections and additional cuts would change my generated result.
>
> 5. Is it possible to generate for example an fully leptonic ttbar decay at NLO. Something like
> generate p p > t t~ , ( t > b w+ , w+ > l+ vl ) , ( t~ > b~ w- , w- > l- vl~ ) ?
>
> Thank you for your help!
>
> Felix
>
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