MadGraph5_aMC@NLO

Question about SMIN in LO SubProcesses/setcuts.f

Asked by Richard Ruiz

Dear Experts,

I am playing with a user-defined cut on smin at LO and found a line that does not quite make sense. It is near line 480 of SubProcesses/setcuts.f in v2.3.3. You can find this location by grepping for:

c
c Compute Smin (for efficiency
c

The next lines start a do-loop over all external particle pairs and calculates s_min(i,j):

      do i=nincoming+1,nexternal-1
      do j=nincoming+1,nexternal-1
         if(j.lt.i)then
            s_min(i,j) = max(s_min(j,i),s_min(i,j))
         else
            smin=0.0d0**2

However, this last line looks as if it should be instead
s_min(i,j)=0.0d0**2

Otherwise, I do not see the point of the smin do-loop up near lines 275, after the loop that checks if cuts need to be applied. Apologies for the spam.

best,
richard

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi Richard,

I concede that such part of the code is kind of weird and can be done in a more optimal way.
However I do not spot any potential bug associate to it.

Cheers,

Olivier

> On Mar 11, 2016, at 18:02, Richard Ruiz <email address hidden> wrote:
>
> New question #288482 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/288482
>
> Dear Experts,
>
> I am playing with a user-defined cut on smin at LO and found a line that does not quite make sense. It is near line 480 of SubProcesses/setcuts.f in v2.3.3. You can find this location by grepping for:
>
> c
> c Compute Smin (for efficiency
> c
>
> The next lines start a do-loop over all external particle pairs and calculates s_min(i,j):
>
> do i=nincoming+1,nexternal-1
> do j=nincoming+1,nexternal-1
> if(j.lt.i)then
> s_min(i,j) = max(s_min(j,i),s_min(i,j))
> else
> smin=0.0d0**2
>
> However, this last line looks as if it should be instead
> s_min(i,j)=0.0d0**2
>
> Otherwise, I do not see the point of the smin do-loop up near lines 275, after the loop that checks if cuts need to be applied. Apologies for the spam.
>
> best,
> richard
>
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

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