What is p(0,i)?

Asked by Y Zhong on 2017-08-04

Hello,

May I ask a basic question about MG5 / fortran?

I am looking at cut.f and I am confused by the meaning of p(0,i)? At some place, it seems to represent the energy of particle i, e.g.
...
notgood=(p(0,i) .le. emin(i)).or.
...

and at other place it seems to represent the 4-momentum of particle i, e.g.
...
       (abs(rap(p(0,i))) .lt. etamin(i))
...

I wonder which understanding is correct (or both / neither)?

Thanks a lot!

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Last query:
2017-08-04
Last reply:
2017-08-04

Hi,

Both are correct.
When you pass an array to a function, you only have to pass the first element of the array.
You actually pass the pointer to that element and the code therefore know the position of memory of the full array.

Cheers,

Olivier

> On 4 Aug 2017, at 22:03, Y Zhong <email address hidden> wrote:
>
> New question #655310 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/655310
>
> Hello,
>
> May I ask a basic question about MG5 / fortran?
>
> I am looking at cut.f and I am confused by the meaning of p(0,i)? At some place, it seems to represent the energy of particle i, e.g.
> ...
> notgood=(p(0,i) .le. emin(i)).or.
> ...
>
> and at other place it seems to represent the 4-momentum of particle i, e.g.
> ...
> (abs(rap(p(0,i))) .lt. etamin(i))
> ...
>
> I wonder which understanding is correct (or both / neither)?
>
> Thanks a lot!
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Can you help with this problem?

Provide an answer of your own, or ask Y Zhong for more information if necessary.

To post a message you must log in.