Number of jobs

Hi,

That’s not a naive question but a very technical one.
So yes the way to perform the phase-space integration depends first of the number of independent Feynman diagram, but also of the mass-spectrum.

Let me take an example, The HWW vertex (like in p p > h > e+ ve mu- vm~), has two very different regime if the higgs mass is below the two W mass.
The first one when the higgs is on shell and the second one when he is off-shell.
Those two regime needs to be integrated separately to provide an accurate (and fast) generation of events.
On the other hand, the second regime is negligeable if the H mass is above the threshold and therefore only one integration channel is required.

Cheers,

Olivier

On Apr 28, 2014, at 6:16 AM, WiWi <email address hidden> wrote:

> New question #247802 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/247802
>
> Hi:
> I have a naive question.
> In my first feeling, the number of Jobs calculating the CS and generating events is related to the number of Feynman Diagrams. But it seems that it is also related to the parameters in the param_card.dat. I'm curious about this. And In my case, there are only few differents between two parameter cards.
> I'm sorry I didn't know the detail about calculating CS in MG5, and this may be a naive question.
> Thanks
>
>
> WiWi
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi:
    Thanks very much!
     So if the mass of mother particle is a little bit larger than the threshold and the difference is comparable to the width of the particle, it still needs to integral both regime. Right?

     Further, what if the particle is on-shell produced and on-shell decayed? like p p > h, h > e+ ve mu- vm~ ? Or this syntax is not recommend?

Best

WiWi

Hi,

> So if the mass of mother particle is a little bit larger than the threshold and the difference is comparable to the width of the particle, it still needs to integral both regime. Right?

Actually, I don’t know the exact formula which is used to decide if we use one or more channel.
In any case, the exact moment where we use more channel is everything but important since the physics is not
impacted by that choice (only the efficiency of the code).

> Further, what if the particle is on-shell produced and on-shell
> decayed? like p p > h, h > e+ ve mu- vm~ ? Or this syntax is not
> recommend?

This is a recommended way to generate this process.
In this case, they are still a potential splitting since both W can’t be on shell simultaneously if the Higgs mass is below the threshold.

Cheers,

Olivier

On Apr 28, 2014, at 3:36 PM, WiWi <email address hidden> wrote:

> Question #247802 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/247802
>
> Status: Answered => Open
>
> WiWi is still having a problem:
> Hi:
> Thanks very much!
> So if the mass of mother particle is a little bit larger than the threshold and the difference is comparable to the width of the particle, it still needs to integral both regime. Right?
>
> Further, what if the particle is on-shell produced and on-shell
> decayed? like p p > h, h > e+ ve mu- vm~ ? Or this syntax is not
> recommend?
>
>
> Best
>
> WiWi
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.