MadGraph5_aMC@NLO

The computing process works fine in LO process generation, but failed to run in NLO generation that runs in LO mode

Asked by CYLiu

I have generated a same sign w boson scattering process in LO with the command

```
import model loop_sm-no_b_mass
generate p p > w+ w+ j j QCD=0
output wwjj-lo
launch
analysis = OFF
```

It works fine and the cross section is computed in about 10 minutes.

But when I generated NLO processes with the command
```
set complex_mass_scheme True
import model loop_sm-no_b_mass
generate p p > w+ w+ j j QCD=0 [QCD]
output wwjj-nlo
launch

order = LO
fixed_order = OFF
shower = OFF
madanalysis = OFF
done

set pdlabel lhapdf
set lhaid 13000
set dynamical_scale_choice 3

set jetalgo -1
set jetradius 0.4
```
it's stuck in one computing process for many hours. I'm wondering why this is so different from generating the process at LO.

Many thanks!

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MadGraph5_aMC@NLO Edit question
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Solved by:
Olivier Mattelaer
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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Yeah that process can not be handle with our code due to the top resonances that occur within the real.
This is possible in four flavor but not in five.

Another solution is to use the MADSTR plugin (which I do not know personally) which offers various way to remove the resonance contribution.

Cheers,

Olivier

Revision history for this message
CYLiu (liu-cy) said (last edit ): 		#2

Thanks for your reply, but I don't understand the contribution of top quark as the log shows there's no process related to top quark. Besides, in this paper ATL-PHYS-PUB-2019-004 page 4 they offered this command and got results.

```
INFO: Generating FKS-subtracted matrix elements for born process: u u > w+ w+ d d QCD<=1 QED<=99 QCD^2=2 QED^2=198 (1 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: u c > w+ w+ d s QCD<=1 QED<=99 QCD^2=2 QED^2=198 (2 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: u d~ > w+ w+ d u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (3 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: u d~ > w+ w+ s c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (4 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: u s~ > w+ w+ d c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (5 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: c u > w+ w+ d s QCD<=1 QED<=99 QCD^2=2 QED^2=198 (6 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: c c > w+ w+ s s QCD<=1 QED<=99 QCD^2=2 QED^2=198 (7 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: c d~ > w+ w+ s u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (8 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: c s~ > w+ w+ d u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (9 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: c s~ > w+ w+ s c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (10 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: d~ u > w+ w+ d u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (11 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: d~ u > w+ w+ s c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (12 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: d~ c > w+ w+ s u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (13 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: d~ d~ > w+ w+ u~ u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (14 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: d~ s~ > w+ w+ u~ c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (15 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: s~ u > w+ w+ d c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (16 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: s~ c > w+ w+ d u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (17 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: s~ c > w+ w+ s c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (18 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: s~ d~ > w+ w+ u~ c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (19 / 20)
INFO: Generating FKS-subtracted matrix elements for born process: s~ s~ > w+ w+ c~ c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (20 / 20)
```

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

Well, the command in that paper does not match the one that you quote above.

First, the paper does indeed the computation in four flavor and not in five.
Second, it does decay the W, which is mandatory if you use the complex mass scheme.

Finally, your command above should include the b quark in the initial/final state since otherwise this will break NLO accuracy with massless b quark.

Cheers,

Olivier

> On 17 Dec 2022, at 08:05, CYLiu <email address hidden> wrote:
>
> Question #704128 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/704128
>
> CYLiu posted a new comment:
> Thanks for your reply, but I don't understand the contribution of top
> quark as the log shows there's no process related to top quark. Besides,
> in this paper arXiv:1803.07943v2 page 4 they offered this command and
> got results.
>
> ```
> INFO: Generating FKS-subtracted matrix elements for born process: u u > w+ w+ d d QCD<=1 QED<=99 QCD^2=2 QED^2=198 (1 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: u c > w+ w+ d s QCD<=1 QED<=99 QCD^2=2 QED^2=198 (2 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: u d~ > w+ w+ d u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (3 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: u d~ > w+ w+ s c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (4 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: u s~ > w+ w+ d c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (5 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: c u > w+ w+ d s QCD<=1 QED<=99 QCD^2=2 QED^2=198 (6 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: c c > w+ w+ s s QCD<=1 QED<=99 QCD^2=2 QED^2=198 (7 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: c d~ > w+ w+ s u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (8 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: c s~ > w+ w+ d u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (9 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: c s~ > w+ w+ s c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (10 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: d~ u > w+ w+ d u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (11 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: d~ u > w+ w+ s c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (12 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: d~ c > w+ w+ s u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (13 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: d~ d~ > w+ w+ u~ u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (14 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: d~ s~ > w+ w+ u~ c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (15 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: s~ u > w+ w+ d c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (16 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: s~ c > w+ w+ d u~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (17 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: s~ c > w+ w+ s c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (18 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: s~ d~ > w+ w+ u~ c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (19 / 20)
> INFO: Generating FKS-subtracted matrix elements for born process: s~ s~ > w+ w+ c~ c~ QCD<=1 QED<=99 QCD^2=2 QED^2=198 (20 / 20)
> ```
>
> --
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Revision history for this message
CYLiu (liu-cy) said : 		#4

Thanks for your detailed explanation!

Revision history for this message
CYLiu (liu-cy) said : 		#5

Thanks Olivier Mattelaer, that solved my question.