generate a process but no events file exist

Asked by Halley Xiong on 2020-11-23

Hello, experts
     I generate a process with model loop_qcd_qed_sm for electroweak correction at NLO, but after I output the process and check the file, there is no events file and html file , I wonder why it's different with p p > t t~ process whose output file includes those two files.

   Best wishes!
   Halley

Question information

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MadGraph5_aMC@NLO Edit question
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Last query:
2020-12-01
Last reply:
2020-12-01

Electroweak correction at NLO are only possible (so far) at fixed order accuracy.
This means that no event generation are possible (this requires NLO+PS accuracy).

I will take a look for the html, Electroweak release is still in beta and therefore it is really nice for you to test and give us feedback.

Cheers,

Olivier

> On 23 Nov 2020, at 08:10, Halley Xiong <email address hidden> wrote:
>
> New question #694138 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/694138
>
> Hello, experts
> I generate a process with model loop_qcd_qed_sm for electroweak correction at NLO, but after I output the process and check the file, there is no events file and html file , I wonder why it's different with p p > t t~ process whose output file includes those two files.
>
> Best wishes!
> Halley
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Halley Xiong (neuromance) said : #2

Thanks, Olivier.
Whether it means that I cannot find the feynman diagrams in output files due to no html file? I tried to display diagrams directly in the terminal program , but the diagrams cannot display completely.

Regards,

Halley

Hi,

So i have done the following.
Since you speak about Electroweak correction, I have used 3.0.3 version (the only one able to do EW correction at fixed-order NLO).

./bin/mg5_aMC
then typed
generate p p > t t~ [QED]
output XXX

and then I have correctly the XXX/info.html file

Cheers,

Olivier

> On 1 Dec 2020, at 08:05, Halley Xiong <email address hidden> wrote:
>
> Question #694138 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/694138
>
> Status: Answered => Open
>
> Halley Xiong is still having a problem:
> Thanks, Olivier.
> Whether it means that I cannot find the feynman diagrams in output files due to no html file? I tried to display diagrams directly in the terminal program , but the diagrams cannot display completely.
>
> Regards,
>
> Halley
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Halley Xiong (neuromance) said : #4

Hello, I installed 2.8 version of mg5. But since I import model loop_qcd_qed_sm, it seems that process with EW correction at NLO can be generated. If it means that I have to install 3.0.3 version so that the html file can exist?

Regards,

Halley

With 2.8,

You will not have EW corrections this is not implemented in that version.
I guess i do not understand what your issue is.
Could you be more specific:
1) what command do you run
(and maybe explain what you want from those syntax since this is likely not what you expect that the code is doing)

2) what is the error message (if any)
3) where do you expect an html page? (or other)
4) on which os/python version/ ... are you running?

Cheers,

Olivier

> On 1 Dec 2020, at 10:41, Halley Xiong <email address hidden> wrote:
>
> Question #694138 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/694138
>
> Status: Answered => Open
>
> Halley Xiong is still having a problem:
> Hello, I installed 2.8 version of mg5. But since I import model
> loop_qcd_qed_sm, it seems that process with EW correction at NLO can be
> generated. If it means that I have to install 3.0.3 version so that the
> html file can exist?
>
> Regards,
>
> Halley
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Halley Xiong (neuromance) said : #6

Sorry I didn't make myself clear.
I run the command " import loop_qcd_qed_sm --> generate e- u > e- u h [QED] " . I wish generate this process with NLO electroweak correction. Then I run " display diagrams " to see the feynman diagrams of this process, but just some of diagrams( about 90 I guess) appear and do not display completely(around 130). So I run "output eu-euh " and check this output file but no html file exists.
My python version is 3.8 and mg5 2.8.

Regards,
Halley

Hi,

Within 2.8.x

I have the following when running your command:
> Command "generate e- u > e- u h [QED] " interrupted in sub-command:
> "generate e- u > e- u h [QED]" with error:
> InvalidCmd : MG5aMC can only handle QCD at NLO accuracy.
> We can however compute loop with [virt=QED].
> We can also compute cross-section for loop-induced processes with [noborn=QED]
> Please report this bug on https://bugs.launchpad.net/mg5amcnlo
> More information is found in 'MG5_debug'.
> Please attach this file to your report.

so it is crashes (as it should)

In 3.0.2:

You should not the following warning since your process is not compatible with NLO accuracy:

WARNING: Use of multiparticles is non-trivial for NLO process generation and depends on the orders included, the process considered, as well as the PDF set chosen. See appendix D of arXiv:1804.10017 [hep-ph] for some guidance.

Cheers,

Olivier

> On 1 Dec 2020, at 13:11, Halley Xiong <email address hidden> wrote:
>
> generate e- u > e- u h [QED]

Halley Xiong (neuromance) said : #8

Sorry , I misremembered.
It's " generate e- u > e- u h [virt=QED] "

Hi,

so this mode is a special mode where you ONLY have the virtual matrix-element.
In that mode you can only compute the loop for a single phase-space point (or more than one actually)
and you get as result both the finite part of the computation but also the pole contribution
(such computation is obviously infinite)

Indeed in that mode we do not have any html output.
For the loop display some identical loop might be merge into a single loop.
I can assign the MadLoop author to give you more details if you need more details.

But independently of those issues, this command does NOT allow you to compute NLO EW correction.
(just the loop)

Cheers,

Olivier

> On 1 Dec 2020, at 13:55, Halley Xiong <email address hidden> wrote:
>
> Question #694138 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/694138
>
> Status: Answered => Open
>
> Halley Xiong is still having a problem:
> Sorry , I misremembered.
> It's " generate e- u > e- u h [virt=QED] "
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Halley Xiong (neuromance) said : #10

Thank you very much.
If mg5 can only compute NLO QCD correction?

Can you help with this problem?

Provide an answer of your own, or ask Halley Xiong for more information if necessary.

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