MadGraph5_aMC@NLO

bwcutff for top pair production

Asked by mathieu.buchkremer@uclouvain.be

Dear MG team,

With MG 1.5.8., I am generating top pair production with pp > w+ b w- b~ , where only off-shell top quarks are involved as intermediary particles. In principle, the cross section has to get smaller as the "bwcutoff" parameter in the run_card.dat becomes smaller.

In order to be consistent with the NWA, I would like to know a) what is the original motivation for bwcutoff to be set to 15 by default, and b) if increasing this parameter to very large values is a valid thing to do. For instance, setting it to 100000, it seems that the cross-sections with (New Physics) resonances and without resonances lead to the same results ! Therefore, is it safe to enlarge bwcutoff without losing important information in the process ?

Thanks,

Mathieu

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
Last query:
Last reply:
Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi Matthieu,

The following MG5 tutorial:
https://cp3.irmp.ucl.ac.be/projects/madgraph/attachment/wiki/TASISchool13/13_06_10_tutomg_tasi.pdf
contains a lot of (slides of) discussion on bwcutoff.

And you have one plot showing the motivation for 15 ( for Z physics).

If you have some doubt on one of your question, don't hesitate to ask more.

Cheers,

Olivier

On Jun 21, 2013, at 6:56 AM, <email address hidden> <email address hidden> wrote:

> New question #231135 on MadGraph5:
> https://answers.launchpad.net/madgraph5/+question/231135
>
> Dear MG team,
>
> With MG 1.5.8., I am generating top pair production with pp > w+ b w- b~ , where only off-shell top quarks are involved as intermediary particles. In principle, the cross section has to get smaller as the "bwcutoff" parameter in the run_card.dat becomes smaller.
>
> In order to be consistent with the NWA, I would like to know a) what is the original motivation for bwcutoff to be set to 15 by default, and b) if increasing this parameter to very large values is a valid thing to do. For instance, setting it to 100000, it seems that the cross-sections with (New Physics) resonances and without resonances lead to the same results ! Therefore, is it safe to enlarge bwcutoff without losing important information in the process ?
>
>
> Thanks,
>
> Mathieu
>
> --
> You received this question notification because you are a member of
> MadTeam, which is an answer contact for MadGraph5.

Revision history for this message
mathieu.buchkremer@uclouvain.be (mathieu-buchkremer) said : 		#2

Thanks Olivier Mattelaer, that solved my question.