MadGraph5_aMC@NLO

Matching and jets from decay chain syntax

Asked by Hannah Banks

Hello,
I'd really appreciate it if someone could give me a hand with this!

I am trying to generate the following BSM process, working in a 5 flavour scheme

p p > zp, zp > b b~

add process p p > zp j, zp > b b~

I am showering with pythia8 and matching.

However, I am unsure as to what to set the parameter nJetMax in the pythia run card - should it be 3 (i.e. should the b's be included in the matching as they are light jets) or should it be 1?

In the pythia manual it says that "ME samples with different jet multiplicities are run through the event generator, and the generation is interrupted after parton showers have been applied, but before resonance decays and beam remnants have been processed."
does this mean that I should not include the b's in the matching and therefore set nJetMax = 1?

When looking at the djr plots (in the HTML folder), I only seem to get a cross over between the 0 sample and 1 sample when considering the transition from the 2nd to 3rd jet (djr 23) and 3rd to 4th jet (djr 34) - is this because the b's are included in these graphs, and therefore when checking for smoothness etc I only need to look at these latter two plots?

Thanks very much for all of your help - I really appreciate it!

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

You should put njmax to one in this case, decay products are not part of the matching/merging procedure.

Cheers,

Olivier

> On 8 Mar 2021, at 14:41, Hannah Banks <email address hidden> wrote:
>
> New question #695916 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/695916
>
> Hello,
> I'd really appreciate it if someone could give me a hand with this!
>
> I am trying to generate the following BSM process, working in a 5 flavour scheme
>
> p p > zp, zp > b b~
>
> add process p p > zp j, zp > b b~
>
> I am showering with pythia8 and matching.
>
> However, I am unsure as to what to set the parameter nJetMax in the pythia run card - should it be 3 (i.e. should the b's be included in the matching as they are light jets) or should it be 1?
>
> In the pythia manual it says that "ME samples with different jet multiplicities are run through the event generator, and the generation is interrupted after parton showers have been applied, but before resonance decays and beam remnants have been processed."
> does this mean that I should not include the b's in the matching and therefore set nJetMax = 1?
>
> When looking at the djr plots (in the HTML folder), I only seem to get a cross over between the 0 sample and 1 sample when considering the transition from the 2nd to 3rd jet (djr 23) and 3rd to 4th jet (djr 34) - is this because the b's are included in these graphs, and therefore when checking for smoothness etc I only need to look at these latter two plots?
>
> Thanks very much for all of your help - I really appreciate it!
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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