MadGraph5_aMC@NLO

Squared order contraints in decay (NP^2==0, 1 and 2) not supportd?

Asked by Tobias Klingl

Hello,

when trying to generate BSM events using the SMEFT with the following syntax

  set gauge unitary
  set group_subprocesses True
  define p = g u c d s u~ c~ d~ s~
  define j = g u c d s u~ c~ d~ s~
  define jb = g u c d s b u~ c~ d~ s~ b~
  generate p p > h QED=1 NP=1 NP^2==2, h > l+ l- l+ l- @0
  add process p p > h jb QED=1 NP=1 NP^2==2, h > l+ l- l+ l- @1
  add process p p > h jb jb QED=1 NP=1 NP^2==2, h > l+ l- l+ l- @2

i am getting the following error: MadGraph5Error : Decay processes cannot specify squared orders constraints
Maybe the stuff i am trying to do here is just not supported as the error message suggests. However, when generating a production-only sample:

  set gauge unitary
  set group_subprocesses True
  define p = g u c d s u~ c~ d~ s~
  define j = g u c d s u~ c~ d~ s~
  define jb = g u c d s b u~ c~ d~ s~ b~
  generate p p > h QED=1 NP=1 NP^2==2 @0
  add process p p > h jb QED=1 NP=1 NP^2==2 @1
  add process p p > h jb jb QED=1 NP=1 NP^2==2 @2

and a decay-only sample:

  set gauge unitary
  set group_subprocesses True
  generate h > l+ l- l+ l- NP=1 NP^2==2

both work fine. Is there a way to generate both processes at the same time?

Best regards,
Tobias

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

What you can do in this case (higgs decay) is

> set gauge unitary
> set group_subprocesses True
> define p = g u c d s u~ c~ d~ s~
> define j = g u c d s u~ c~ d~ s~
> define jb = g u c d s b u~ c~ d~ s~ b~
> generate p p > h QED=1 NP=1 NP^2==2 @0
> add process p p > h jb QED=1 NP=1 NP^2==2 @1
> add process p p > h jb jb QED=1 NP=1 NP^2==2 @2

> output
> launch
> madspin=none
> decay h > l+ l- l+ l-

This should work (since we never evaluate the full matrix-element.
The madspin=none mode is quite bad in general but is actually perfect in the case of the SM Higgs.

Cheers,

Olivier

> On 10 Apr 2020, at 19:23, Tobias Klingl <email address hidden> wrote:
>
> New question #689823 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/689823
>
> Hello,
>
> when trying to generate BSM events using the SMEFT with the following syntax
>
> set gauge unitary
> set group_subprocesses True
> define p = g u c d s u~ c~ d~ s~
> define j = g u c d s u~ c~ d~ s~
> define jb = g u c d s b u~ c~ d~ s~ b~
> generate p p > h QED=1 NP=1 NP^2==2, h > l+ l- l+ l- @0
> add process p p > h jb QED=1 NP=1 NP^2==2, h > l+ l- l+ l- @1
> add process p p > h jb jb QED=1 NP=1 NP^2==2, h > l+ l- l+ l- @2
>
> i am getting the following error: MadGraph5Error : Decay processes cannot specify squared orders constraints
> Maybe the stuff i am trying to do here is just not supported as the error message suggests. However, when generating a production-only sample:
>
> set gauge unitary
> set group_subprocesses True
> define p = g u c d s u~ c~ d~ s~
> define j = g u c d s u~ c~ d~ s~
> define jb = g u c d s b u~ c~ d~ s~ b~
> generate p p > h QED=1 NP=1 NP^2==2 @0
> add process p p > h jb QED=1 NP=1 NP^2==2 @1
> add process p p > h jb jb QED=1 NP=1 NP^2==2 @2
>
> and a decay-only sample:
>
> set gauge unitary
> set group_subprocesses True
> generate h > l+ l- l+ l- NP=1 NP^2==2
>
> both work fine. Is there a way to generate both processes at the same time?
>
> Best regards,
> Tobias
>
> --
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