the difference between "generate p p > n2 x1-, (n2 > z n1, x1- > w- n1)" and "generate p p > n2 x1-"

Asked by Di Zhang on 2020-01-16

Dear authors,

If Br(n2 > z n1)=1 and Br(x1- > w- n1) in the param_card.dat, what is the difference between "generate p p > n2 x1-, (n2 > z n1, x1- > w- n1)" and "generate p p > n2 x1-" in MadGraph5?

I am looking forward to your reply and thank you in advance.

Your sincerely,
Di Zhang.

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
2020-01-18
Last query:
2020-01-18
Last reply:
2020-01-16

Hi,

MadGraph does not use the BR information at all for such kind of computation.
(which actually allows you to set cut in the final states).

So a crucial parameter for us is the total width. If that parameter is not set to the correct value, the two cross-section will not match.

> "generate p p > n2 x1-, (n2 > z n1, x1- > w- n1)" and "generate p p > n2 x1-" in MadGraph5?

Obviously the main differenc is your final state.
Note that your fist syntax is actually wrong
I guess you want to say
> generate p p > n2 x1-, n2 > z n1, x1- > w- n1

Cheers,

Olivier

> On 16 Jan 2020, at 15:08, Di Zhang <email address hidden> wrote:
>
> New question #688039 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/688039
>
> Dear authors,
>
> If Br(n2 > z n1)=1 and Br(x1- > w- n1) in the param_card.dat, what is the difference between "generate p p > n2 x1-, (n2 > z n1, x1- > w- n1)" and "generate p p > n2 x1-" in MadGraph5?
>
> I am looking forward to your reply and thank you in advance.
>
> Your sincerely,
> Di Zhang.
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Di Zhang (ddou) said : #2

Hi Olivier,

Thank you for your reply soon!

My progress is p p > n2 x1-, n2 > z n1, x1- > w- n1, and I swiched the Pythia8 on. How to set the Br(n2 > z n1)=1 and Br(x1- > w- n1)=1 in MadGraph5?

You said 'the two cross-section will not match' and I am wonder what the two cross section are.

Your sincerely,

Di Zhang.

Hi,

If the Branching ratio is physically one,
then it should be enought to set the width of n2 and x1- to "auto".

Cheers,

Olivier

> On 16 Jan 2020, at 16:13, Di Zhang <email address hidden> wrote:
>
> Question #688039 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/688039
>
> Status: Answered => Open
>
> Di Zhang is still having a problem:
> Hi Olivier,
>
> Thank you for your reply soon!
>
> My progress is p p > n2 x1-, n2 > z n1, x1- > w- n1, and I swiched the Pythia8 on. How to set the Br(n2 > z n1)=1 and Br(x1- > w- n1)=1 in MadGraph5?
>
> You said 'the two cross-section will not match' and I am wonder what the two cross section are.
>
> Your sincerely,
>
> Di Zhang.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Di Zhang (ddou) said : #4

Thanks Olivier Mattelaer, that solved my question.