MadGraph5_aMC@NLO

strong cuts error

Asked by daniel camargo

Hey guys,

I have tried to generate events for p p > Z, Z > l- l+ in the window where 2400 < mll < 3500 [GeV], for that I modified the min and max dilepton invariant mass in the run_card.dat but I got an error of, perhaps, strong cuts. There is another way to generate events for that kind of specific invariant masses windows?

My MG5 version is MG5_aMC_v2_2_3.

PD: I generated another events but using pythia8 and it consumes a lot of space and time machine, why? there is a way to avoid that and make it quick as with the other pythia versions?

thanks
&
Cheers,

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,

Your syntax request the Z to be onshell. (i.e. the invariant mass of the Z should be "close" to be onshell)
Therefore all the code assume that this is the case.
The cut is applied at many place to increase efficiency (including in the way the phase-space generator works). i.e. just changing a cut will not be enough here (you have to change completely the code)

The better way to generate this would be to do
generate p p > Z > l- l+

and see if it goes trough. I would also suggest that you upgrade your version of MG5aMC since a more recent version is likely to be faster (or even to not crash in this case --with the correct syntax of course--)

Obviously, I do not have to warn you that the synatx
generate p p > Z > l- l+
returns what you ask for, but that you miss important contribution in that phase-space region that you consider. (i.e. the contribution of the photon and the interference contribution between the two)
This is the example that I use in most of my tutorial to explain the difference between the various syntax and why using the above syntaz is (typically) a bad idea -- but now I do not know what effect you try to look at and how you plan to include this interference in your analysis)

Cheers,

Olivier

> On 3 Jan 2019, at 16:32, daniel camargo <email address hidden> wrote:
>
> New question #677299 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/677299
>
> Hey guys,
>
> I have tried to generate events for p p > Z, Z > l- l+ in the window where 2400 < mll < 3500 [GeV], for that I modified the min and max dilepton invariant mass in the run_card.dat but I got an error of, perhaps, strong cuts. There is another way to generate events for that kind of specific invariant masses windows?
>
> My MG5 version is MG5_aMC_v2_2_3.
>
> PD: I generated another events but using pythia8 and it consumes a lot of space and time machine, why? there is a way to avoid that and make it quick as with the other pythia versions?
>
> thanks
> &
> Cheers,
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
daniel camargo (dacamargov) said : 		#2

Yes, I tried that syntax already and it worked, but it is in general not safe as you said. I guess for my purpose p p > l- l+ its the better option as it its safe and includes the photon-interference.

Thanks!

Revision history for this message
daniel camargo (dacamargov) said : 		#3

Thanks Olivier Mattelaer, that solved my question.