Is it possible to do Matching and Merging for Particle decay process?

Asked by yicongsui on 2017-09-03

Hi,

I am studying a Dm > b b~ model using madgraph 5 + pythia 8 environment. I have been reading about the matching and merging feature for the program. They seem to be able to avoid double counting and let PS and ME both contribute their best part. I want to know if i could use this matching and merging technique on a decay process. (say DM > b b~).

I have been doing some test about this but keep getting errors but the matching and merging works out fine when i test p p > w j j example.

Best

Yicong

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Last query:
2017-09-03
Last reply:
2017-09-03

Hi,

No matching/merging for those kind of decay are not supported.
This is also typically irrelevant since the PS are typically doing a quite good job in those cases (At least I expect that as long as the mass of the DM is not too heavy)

Cheers,

Olivier

On 3 Sep 2017, at 04:28, yicongsui <email address hidden> wrote:
>
> New question #657323 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/657323
>
> Hi,
>
> I am studying a Dm > b b~ model using madgraph 5 + pythia 8 environment. I have been reading about the matching and merging feature for the program. They seem to be able to avoid double counting and let PS and ME both contribute their best part. I want to know if i could use this matching and merging technique on a decay process. (say DM > b b~).
>
> I have been doing some test about this but keep getting errors but the matching and merging works out fine when i test p p > w j j example.
>
> Best
>
> Yicong
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

yicongsui (trilobite) said : #2

Hi, Olivier

Thank you so much for the quick response. The problem is, i do have a PeV scale DM. Would that make a difference? Also, some question about pythia. Since now that i have a DM > b b~ decay process, there should not be any ISR, right? Could I simply turn this off? Would it mess with my results?

Best

Yicong

Hi Yicong,

> The problem is, i do have a
> PeV scale DM.

Hum ok, I would try to do it manually then.
Generate each multiplicity independently.
And then run Pythia manually on those.
I do not know how much flexible is Pythia.

In worse case scenario, you can
1) use re-weighting approach to change the scale of alphas
2) simply read the hempc output in order to implement the MLM veto.

> Also, some question about
> pythia. Since now that i have a DM > b b~ decay process, there should
> not be any ISR, right? Could I simply turn this off? Would it mess with
> my results?

I'm not a Pythia expert, so this is only based on my experience on that program.
It should be fine in this case to turn it off without any difference in your result.

Cheers,

Olivier

> On 3 Sep 2017, at 19:37, yicongsui <email address hidden> wrote:
>
> Question #657323 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/657323
>
> Status: Answered => Open
>
> yicongsui is still having a problem:
> Hi, Olivier
>
> Thank you so much for the quick response. The problem is, i do have a
> PeV scale DM. Would that make a difference? Also, some question about
> pythia. Since now that i have a DM > b b~ decay process, there should
> not be any ISR, right? Could I simply turn this off? Would it mess with
> my results?
>
> Best
>
> Yicong
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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