# 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?

Di Zhang.

## Question information

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Solved by:
Olivier Mattelaer
Solved:
2020-01-18
Last query:
2020-01-18
2020-01-16
 Olivier Mattelaer (olivier-mattelaer) said on 2020-01-16: #1

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:
>
> 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?
>
>
> Di Zhang.
>
>
> --

 Di Zhang (ddou) said on 2020-01-16: #2

Hi Olivier,

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.

Di Zhang.

 Olivier Mattelaer (olivier-mattelaer) said on 2020-01-16: #3

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:
>
>
> Di Zhang is still having a problem:
> Hi Olivier,
>
>
> 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.
>
>
> Di Zhang.
>
> --