Likelihoods at process level

Asked by Rob Verheyen on 2019-08-16

Dear Madgraph authors,

Is it possible to extract event likelihoods at the process level (so without shower/hadronization/detector) from Madgraph in some straightforward way? That is, the quantity

L = 1/sigma f1(x1,Q1^2) f2(x2,Q2^2) |M|^2 1/2s

I don't believe the event weights are useful in this case because they are folded with the likelihood of the phase space generator. It seems like MadWeight should be able to do this, but as far as I can tell it's not quite what it is meant for.

Thanks,
Rob

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Rob Verheyen
Solved:
2019-08-16
Last query:
2019-08-16
Last reply:
2019-08-16

Hi,

From your formula it seems to be a simplify case from the madweight situation. However madweight is a phase space integrator so if you over simplify to a case that does not need a phase space integration then madweight is useless. (Is it your case?)

If you do not have any phase space integral to evaluate the problem is actually trivial. We do not have/maintain a specific code for that. But you can use the standalone output to evaluate the matrix elements and then multiply yourself by the other factors.

A plug-in of the reweighting module can also be an option but only if you plan to distribute such code (and therefore to provide support for it) . It also as constraints on the input format (lhef)

Cheers,

Olivier

Get Outlook for iOS<https://aka.ms/o0ukef>
________________________________
From: <email address hidden> <email address hidden> on behalf of Rob Verheyen <email address hidden>
Sent: Friday, August 16, 2019 2:02:43 PM
To: Olivier Mattelaer <email address hidden>
Subject: [Question #682941]: Likelihoods at process level

New question #682941 on MadGraph5_aMC@NLO:
https://answers.launchpad.net/mg5amcnlo/+question/682941

Dear Madgraph authors,

Is it possible to extract event likelihoods at the process level (so without shower/hadronization/detector) from Madgraph in some straightforward way? That is, the quantity

L = 1/sigma f1(x,Q^2) f2(x,Q^2) |M|^2 1/2s

I don't believe the event weights are useful in this case because they are folded with the likelihood of the phase space generator. It seems like MadWeight should be able to do this, but as far as I can tell it's not quite what it is meant for.

Thanks,
Rob

--
You received this question notification because you are an answer
contact for MadGraph5_aMC@NLO.

Rob Verheyen (robverheyen) said : #2

Hi Olivier,

Okay, I will build the code myself then. Thanks!