PDF effect on distributions

Asked by Jake on 2018-02-01

Hi,

I would like to estimate the intra-PDF effects on an invariant mass distribution. In other words, I would like to use non-central PDF values to generate events through to Delphes level.

To my understanding, running systematics incorporates the reweighting into errors in the cross-section estimate only. Is there a way to use non-central PDF values/reweighting in the simulation of the event kinematics?

This may be a stretch, but is there furthermore a way to do this that wouldn't require fully rerunning Pythia and Delphes for each reweighting?

Thanks,
Jake

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Last query:
2018-02-01
Last reply:
2018-02-01

Hi Jake,

> To my understanding, running systematics incorporates the reweighting into errors in the cross-section estimate only.

This is not correct, you have the weight for each event (and each PDF set) so you have the full distribution available.

> This may be a stretch, but is there furthermore a way to do this that wouldn't require fully rerunning Pythia and Delphes for each reweighting?

Since pythia can also depend of the PDF, you have to decide how much precise you want your generation.
(Those are actually only PDF ratio which reduce the dependency so to my point of view this is not critical)

So if you decide to neglect those effects, you can use the original weights related to the systematics.
If you want to keep such effects then you have to rerun everything.

Cheers,

Olivier

> On 1 Feb 2018, at 13:09, Jake <email address hidden> wrote:
>
> New question #663955 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/663955
>
> Hi,
>
> I would like to estimate the intra-PDF effects on an invariant mass distribution. In other words, I would like to use non-central PDF values to generate events through to Delphes level.
>
> To my understanding, running systematics incorporates the reweighting into errors in the cross-section estimate only. Is there a way to use non-central PDF values/reweighting in the simulation of the event kinematics?
>
> This may be a stretch, but is there furthermore a way to do this that wouldn't require fully rerunning Pythia and Delphes for each reweighting?
>
> Thanks,
> Jake
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Can you help with this problem?

Provide an answer of your own, or ask Jake for more information if necessary.

To post a message you must log in.