MadGraph5_aMC@NLO

on/off -shell VB question

Asked by Azar Mustafayev

Hello,

I am trying to generate 3-lepton events from WZ at LHC and I am confused about different options. I found there are 3 ways to get this final state
1) p p > w z, w > l nu, z > lp ln
2) p p > w+ z > lp ln l nu
    add process p p > w- z > lp ln l nu
3) p p > lp ln l nu
where w = w+ m-, lp = e+ mu+ ta+, ln = e- mu- ta-, l = e+ mu+ ta+ e- mu- ta-, nu = ve vm vt ve~ vm~ vt~

If understood correctly, the first approach includes only on-shell VBs, and the third one has both on-shell and off-shell VBs. What about the second one, does it include off-shell VBs? If yes, then what is the difference between 2 and 3?

Thank you,
  Azar

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Azar Mustafayev
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Pierre Artoisenet (partois) said : 		#1

Dear Azar,

(3) also includes non resonant diagrams, e.g. diagrams with with the splitting
photon > l+ l- (no Z)

(2) includes only the resonant diagrams with Z > l+ l- , w > l nu
      but the w and z can be offshell (the invariant mass of each resonance
      is generated in the mass window [m_pole -BW_cutoff*Gamma, m_pole + BW_cutoff*Gamma ])

(1) is the same as (2), I think. But I let Olivier confirm this (he is currently offline and will be back on next Sunday)

Cheers,
Pierre

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Azar Mustafayev (azar) said : 		#2

Dear Pierre,
Thank you for the explanatons.
Best,
  Azar

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Olivier Mattelaer (olivier-mattelaer) said : 		#3

Hi Pierre, Azar,

> (1) is the same as (2), I think. But I let Olivier confirm this (he is
> currently offline and will be back on next Sunday)

Concerning the generated diagram you are correct, but
(1) is subject to the bwcutoff of the run_card
while (2) is not subject to this cut.

In most of the case (1) is the correct syntax between (1) and (2).

You will find more information between all those differences in the following tutorial:
https://indico.cern.ch/getFile.py/access?contribId=4&resId=2&materialId=slides&confId=234296

Cheers,

Olivier

On Apr 17, 2013, at 11:41 AM, Pierre Artoisenet <email address hidden> wrote:

> Question #226862 on MadGraph5 changed:
> https://answers.launchpad.net/madgraph5/+question/226862
>
> Status: Open => Answered
>
> Pierre Artoisenet proposed the following answer:
> Dear Azar,
>
> (3) also includes non resonant diagrams, e.g. diagrams with with the splitting
> photon > l+ l- (no Z)
>
> (2) includes only the resonant diagrams with Z > l+ l- , w > l nu
> but the w and z can be offshell (the invariant mass of each resonance
> is generated in the mass window [m_pole -BW_cutoff*Gamma, m_pole + BW_cutoff*Gamma ])
>
> (1) is the same as (2), I think. But I let Olivier confirm this (he is
> currently offline and will be back on next Sunday)
>
> Cheers,
> Pierre
>
> --
> You received this question notification because you are a member of
> MadTeam, which is an answer contact for MadGraph5.

Revision history for this message
Azar Mustafayev (azar) said : 		#4

Hi Oliver,

Thank you for the explanation. And that tutorial is very helpful.

Best,
  Azar