What is p(0,i)?

Asked by Y Zhong on 2017-08-04

Hello,

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!

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2017-08-04
 Olivier Mattelaer (olivier-mattelaer) said on 2017-08-04: #1

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:
>
> Hello,
>
>
> 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!
>
>
> --