Poles don't cancel error and add process command

Asked by Aya Ismail Hosny Beshr

Hi,

I am generating the process: p p > h1 h1 [QCD] using 2HDM_NLO model.

During launch an error appears saying (aMCatNLOError : Poles do not cancel, run cannot continue). I have seen FAQ, I did the supposed solution and it works good, but the warning mentioned here https://answers.launchpad.net/mg5amcnlo/+faq/2720 didn't appear in my case, so what would be the problem causing the error?

A second issue, when I am generating this process ggF of VBF diagrams (responsible for for Higgs production by heavy quark loop via gluon-gluon fusion & vector boson fusion respectively) are not included in the Feynman diagrams? Why? despite using [QCD] corrections?

Could I solve this issue by adding those processes during generation by:

generate p p > h1 h1 [QCD]
add process g g > h1 h1 [QCD]
add process v v > h1 h1 where v = w+ w- z is a multiparticle definition

Does madgraph 5 understand this and will include those processes with the other ones with their contribution and included in the cross section computation or I am thinking wrongly?

Thanks a lot and really appreciating your help!

Best Regards,
Aya

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Aya Ismail Hosny Beshr
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Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#1

Hi,

> During launch an error appears saying (aMCatNLOError : Poles do not cancel, run cannot continue). I have seen FAQ, I did the supposed solution and it works good, but the warning mentioned here https://answers.launchpad.net/mg5amcnlo/+faq/2720 didn't appear in my case, so what would be the problem causing the error?

Probably an issue with the model.
Please check the documentation associated with the model to see if they have omitted terms/... and contact the model author to see what the issue can be.

> A second issue, when I am generating this process ggF of VBF diagrams (responsible for for Higgs production by heavy quark loop via gluon-gluon fusion & vector boson fusion respectively) are not included in the Feynman diagrams? Why? despite using [QCD] corrections?

[QCD] means NLO computation in QCD.
if/When we do not find any born contribution at tree-level, we automatically switch to the syntax
[noborn=QCD] which triggers the LO computation of the loop-induced process

In the case of
add process p p > h1 h1 [QCD]
the loop induced contribution
g g > h1 h1 (via some loop)
is technically a NNLO term and therefore is not include in the NLO computation.

You can not do
> generate p p > h1 h1 [QCD]
> add process g g > h1 h1 [noborn=QCD]

Since the two mode of computations are quite different (one is LO like and the other is NLO)
and therefore the run_card are not compatible (and a lot of other stuff as well)

If you want to have both predictions, you would need to generate them separatly.

> add process v v > h1 h1 where v = w+ w- z is a multiparticle definition

I guess what you want in this case is
> generate p p > j j h1 h1 QCD=0
but not sure what you ask for here.

Cheers,

Olivier

> On 1 Apr 2020, at 18:57, Aya Ismail Hosny Beshr <email address hidden> wrote:
>
> New question #689641 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/689641
>
> Hi,
>
> I am generating the process: p p > h1 h1 [QCD] using 2HDM_NLO model.
>
> During launch an error appears saying (aMCatNLOError : Poles do not cancel, run cannot continue). I have seen FAQ, I did the supposed solution and it works good, but the warning mentioned here https://answers.launchpad.net/mg5amcnlo/+faq/2720 didn't appear in my case, so what would be the problem causing the error?
>
> A second issue, when I am generating this process ggF of VBF diagrams (responsible for for Higgs production by heavy quark loop via gluon-gluon fusion & vector boson fusion respectively) are not included in the Feynman diagrams? Why? despite using [QCD] corrections?
>
> Could I solve this issue by adding those processes during generation by:
>
> generate p p > h1 h1 [QCD]
> add process g g > h1 h1 [QCD]
> add process v v > h1 h1 where v = w+ w- z is a multiparticle definition
>
> Does madgraph 5 understand this and will include those processes with the other ones with their contribution and included in the cross section computation or I am thinking wrongly?
>
> Thanks a lot and really appreciating your help!
>
> Best Regards,
> Aya
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Aya Ismail Hosny Beshr (ayaa) said :
#2

Hi Olivier,

Thanks a lot for your clear explanation!

For the process: v v > h1 h1, it is vector boson fusion
Where 2 quarks each emit a W or Z slecificaly and anihilate together giving higgs boson. So, what I meant by this is starting the process from the the two bosons fusion W or Z directly, but I guess this is not correct?

Best Regards,
Aya

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#3

No this would not work...
You would need a PDF that support W/Z in initial state which does not exists
(even if it does we do not support such type of PDF so far)

Cheers,

Olivier

> On 2 Apr 2020, at 14:04, Aya Ismail Hosny Beshr <email address hidden> wrote:
>
> Question #689641 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/689641
>
> Aya Ismail Hosny Beshr posted a new comment:
> Hi Olivier,
>
> Thanks a lot for your clear explanation!
>
> For the process: v v > h1 h1, it is vector boson fusion
> Where 2 quarks each emit a W or Z slecificaly and anihilate together giving higgs boson. So, what I meant by this is starting the process from the the two bosons fusion W or Z directly, but I guess this is not correct?
>
> Best Regards,
> Aya
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Aya Ismail Hosny Beshr (ayaa) said :
#4

Yah I see! I got it. Thanks a lot for your help

Best Regards,
Aya