Reweighting merged lhe file

Asked by Yannis Maznas on 2018-06-27

Dear MG experts,

I've run several projects (same proc/run/param cards) and in the end I merged all the lhe files. (v2.6.1)

Is there a way to reweight the final file?

I tried copying the final lhe along with its banner into one of the Event/run_01 folders and run the reweighting there as if it was generated there. This does not seem to work though.

It ends normally (without errors) but it's as if it does not affect the lhe file (except its size) or the param_card.dat file at all. Madanalysis plots show no difference between original and final one.

Any workaround?

Best regards,
Yannis

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2018-06-28
Last query:
2018-06-28
Last reply:
2018-06-28

Hi,

> but it's as if it does not affect the lhe file (except its size)

Which means it does affects the file.

> Madanalysis plots show no difference between original and final one.

That code is not able to plot weights (but the central one).
So you can not use that code in that context.

So my guess it that everything is running as expected. If you want to do the plot with MA5, then you need
to setup the reweighting code to change the central weight of the sample via the reweighting option
change ouptut 2.0

To be fully sure that something happens, can you do a diff of the two files (before and after)

Cheers,

Olivier

> On 27 Jun 2018, at 10:42, Yannis Maznas <email address hidden> wrote:
>
> New question #670498 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/670498
>
> Dear MG experts,
>
> I've run several projects (same proc/run/param cards) and in the end I merged all the lhe files. (v2.6.1)
>
> Is there a way to reweight the final file?
>
> I tried copying the final lhe along with its banner into one of the Event/run_01 folders and run the reweighting there as if it was generated there. This does not seem to work though.
>
> It ends normally (without errors) but it's as if it does not affect the lhe file (except its size) or the param_card.dat file at all. Madanalysis plots show no difference between original and final one.
>
> Any workaround?
>
> Best regards,
> Yannis
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Yannis Maznas (imaznas) said : #2

Hi Olivier,

> Which means it does affects the file.

Well diff showed no difference between the two files but in the end the problem was that I was trying to reweight samples generated by v2.6.3 with v2.6.1.

In v2.6.1 it seems to be working fine.

Could you elaborate a bit on the "change ouptut 2.0" option.
Indeed I see differences in madanalysis now. Does it mean that it affects the kinematics or is it just an internal madanalysis feature to treat weights from lhe files?

Cheers,
Yannis

Hi,

> Could you elaborate a bit on the "change ouptut 2.0" option.

All event have the "central" weight. This is mandatory in the lhe convention since version 1.0 of the convention
Since version 3.0 it was also allowed to have additional weight corresponding to various scenario (different BSM, PDF, scale,...)

So setting the output format to "2.0" forbids to use those additional weight and in that case, we directly modify the central weight. (and therefore we loose the information of the original scenario)

MadAnalysis is only able to plot the events for the central weight.

Cheers,

Olivier

> On 28 Jun 2018, at 12:07, Yannis Maznas <email address hidden> wrote:
>
> Question #670498 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/670498
>
> Status: Answered => Open
>
> Yannis Maznas is still having a problem:
> Hi Olivier,
>
>> Which means it does affects the file.
>
> Well diff showed no difference between the two files but in the end the
> problem was that I was trying to reweight samples generated by v2.6.3
> with v2.6.1.
>
> In v2.6.1 it seems to be working fine.
>
>
> Could you elaborate a bit on the "change ouptut 2.0" option.
> Indeed I see differences in madanalysis now. Does it mean that it affects the kinematics or is it just an internal madanalysis feature to treat weights from lhe files?
>
> Cheers,
> Yannis
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Yannis Maznas (imaznas) said : #4

Thanks Olivier Mattelaer, that solved my question.