Got some warming when generate events with closing most of the initial cuts

Hi ParticleCat,

I never face such warning.
But quite often warning starting with Note:
are generated by firefox.
Could you run the code with automatic_html_opening=False
just to be sure that this is not connected to the browser?

Cheers,

Olivier
On Mar 31, 2014, at 7:16 AM, ParticleCat <email address hidden> wrote:

> New question #246278 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/246278
>
> When I generate events as closing most of the initial cuts I get some "Note" between each channels.
>
> Note: The following floating-point exceptions are signalling: IEEE_INVALID_FLAG
>
> Did this cause any trouble with the final result ?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

Sorry that I'm a noob on the program.
Where should I set the variable automatic_html_opening=False

Regards,
Bob

Hi Olivier,

I disable the automatic_html_opening in mg5_configuration.txt but it still have the warning message.

As an example, when I generate p p > j j and disable all the cuts.
I got the warning message.

Regards,
Bob

Hi Bob,

If you remove all the cuts, the computation does not make any sense at LO since the result is formally infinite due to —in particular— to soft and collinear divergencies.
Could you try with default cut?

In that case I have:
7.453e+08 ± 1.7e+06

Cheers,

Olivier

On Apr 2, 2014, at 9:01 AM, ParticleCat <email address hidden> wrote:

> Question #246278 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/246278
>
> ParticleCat gave more information on the question:
> Hi Olivier,
>
> I disable the automatic_html_opening in mg5_configuration.txt but it
> still have the warning message.
>
> As an example, when I generate p p > j j and disable all the cuts.
> I got the warning message.
>
> Regards,
> Bob
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

I want to compare the physics between some events.
The cuts will make the comparison very difficult and the physics is behind the cut.
I want to do the process p p > e+ e- w and p p > z w (z > e+e-) with checking the branching ratio.
Although I got the right ratio with removing all the cut, I was confused by the warning.
Thanks for solving the question for me.
It seems the divergencies won't affect the ratio.

Regards,
Bob

Hi Bob,

> I want to compare the physics between some events.
> The cuts will make the comparison very difficult and the physics is behind the cut.

I agree but the cut are necessary to remove some unphysical divergencies. If you left uncured the divergencies it means that you consider
part of the phase-spce where you process is unphysical and therefore what you do does not make sense.
This is particularly True for the process p p > j j that you where mentioning. Indeed you have the soft and the collinear divergencies, so if you want to go soft, you are force to
move to an NLO computation instead of a LO one. But even in NLO computation you need some cut to prevent the NNLO divergencies.

> I want to do the process p p > e+ e- w and p p > z w (z > e+e-) with checking the branching ratio.

For the first process, if you don’t put any cut on the electron then you probably have not finite result due to the photon divergencies.
The second process makes sense only if the Z is (loosely) on-shell since otherwise the interference effect start to be non-negligeable.
Note that your two samples overlaps.
A way to circumvent this is to use the following syntax
> p p > e+ e- w $ z
and
> p p > z w (z > e+e-)

In the first case, the Z is forbidden to be on-shell, while in the second case it is force to be (each time loosely)

More information:
https://cp3.irmp.ucl.ac.be/projects/madgraph/attachment/wiki/MGTalks/13_06_10_tutomg_tasi.pdf

Cheers,

Olivier

On Apr 4, 2014, at 7:11 AM, ParticleCat <email address hidden> wrote:

> Question #246278 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/246278
>
> Status: Answered => Solved
>
> ParticleCat confirmed that the question is solved:
> Hi Olivier,
>
> I want to compare the physics between some events.
> The cuts will make the comparison very difficult and the physics is behind the cut.
> I want to do the process p p > e+ e- w and p p > z w (z > e+e-) with checking the branching ratio.
> Although I got the right ratio with removing all the cut, I was confused by the warning.
> Thanks for solving the question for me.
> It seems the divergencies won't affect the ratio.
>
> Regards,
> Bob
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.