SubProcesses doesn't have available phase-space.

Asked by Emily Thompson on 2020-09-16

Dear MadGraph experts,

I am trying to generate RPV SUSY events with MG version 2.6.7. The process string is:

process = '''
import model RPVMSSM_UFO
define susylq = ul ur dl dr cl cr sl sr
define susylq~ = ul~ ur~ dl~ dr~ cl~ cr~ sl~ sr~
generate p p > t1 t1~ j j $ go susylq susylq~ b1 b2 t2 b1~ b2~ t2~
'''
This fails with the error: "P1_gg_t1t1xgg SubProcesses doesn't have available phase-space. Please check mass spectrum."

Interestingly, the generation of the problematic subprocesses alone (g g > t1 t1~ g g ) works just fine.

I've found that setting QED=0 also solves the issue, however I do not understand why QED couplings are causing an issue here.

Does anyone have an idea why this is happening?

Thank you,
Emily

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
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Last query:
2020-10-07
Last reply:
2020-10-08

Could you check the latest version.
This remind me an old bug, So it is quite likely that updating your version of MG5aMC will solve that issue.

Cheers,

Olivier

> On 16 Sep 2020, at 19:10, Emily Thompson <email address hidden> wrote:
>
> New question #692961 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/692961
>
> Dear MadGraph experts,
>
> I am trying to generate RPV SUSY events with MG version 2.6.7. The process string is:
>
> process = '''
> import model RPVMSSM_UFO
> define susylq = ul ur dl dr cl cr sl sr
> define susylq~ = ul~ ur~ dl~ dr~ cl~ cr~ sl~ sr~
> generate p p > t1 t1~ j j $ go susylq susylq~ b1 b2 t2 b1~ b2~ t2~
> '''
> This fails with the error: "P1_gg_t1t1xgg SubProcesses doesn't have available phase-space. Please check mass spectrum."
>
> Interestingly, the generation of the problematic subprocesses alone (g g > t1 t1~ g g ) works just fine.
>
> I've found that setting QED=0 also solves the issue, however I do not understand why QED couplings are causing an issue here.
>
> Does anyone have an idea why this is happening?
>
> Thank you,
> Emily
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Emily Thompson (eat4978) said : #2

Dear Olivier,

Thank you for your quick response. I can confirm that the problem persists with the latest version (v2.8.1). Setting QED=0 still solves the issue, though I am unsure why. Though the generation is working by setting QED=0, I would like to understand why the error occurs to make sure that there are not other underlying issues.

Cheers,
Emily

Hi,

I do not reproduce the issue with 2.8.1. Did you use the default benchmark of the model?
If not could you send me your benchmark point (and potentially also run_card if not default as well).

> Setting QED=0 still solves the issue, though I am unsure why. Though the generation is working by setting QED=0, I would like to understand why the error occurs to make sure that there are not other underlying issues.

QED=0 is the default anyway (more exactly setting QED as small as possible is the the default, which in this case means 0) so it should not have any impact.

Cheers,

Olivier

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