"@0" usage with decay chains

> 1) does "@0 NP<=1" avoid to have processes with NP==1 both in production and decay part in all of the 3 previous MG strings?

Yes.

> 2) if the previous syntax does what I expect, does exist a way to do the same thing but by managing decays by means of madspin?

Currently no.
Is it possible to implement: yes ( I think I did implement this in the past actually)
Is it working? that's were madspin is dubious, you are likely to have weird situation in madspin that will at best kill the efficiency or at worse bias your result.

Cheers,

Olivier

> On 16 Dec 2020, at 11:50, Riccardo <email address hidden> wrote:
>
> New question #694542 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/694542
>
> Dear experts,
>
> I am using MG5 v2.6.5 together with SMEFTsim_A_U35_MwScheme_UFO_v3_1 model. I would like to generate a "p p > l+ l- j j j j" EWK process with 0 or 1 New Physics vertex, but I need to fix the intermediate vector bosons in order to avoid too much time consuming calculations.
> Is the following syntax correct?
>
> generate p p > z z j j QCD=0 SMHLOOP=0 NP<=1, z > l+ l- NP<=1, z > j j NP<=1 @0 NP<=1
> add process p p > z w+ j j QCD=0 SMHLOOP=0 NP<=1, z > l+ l- NP<=1, w+ > j j NP<=1 @0 NP<=1
> add process p p > z w- j j QCD=0 SMHLOOP=0 NP<=1, z > l+ l- NP<=1, w- > j j NP<=1 @0 NP<=1
>
> So my questions are :
> 1) does "@0 NP<=1" avoid to have processes with NP==1 both in production and decay part in all of the 3 previous MG strings?
> 2) if the previous syntax does what I expect, does exist a way to do the same thing but by managing decays by means of madspin?
>
> Thanks for your help.
>
> Kind Regards,
>
> Riccardo
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Dear Olivier,

If I prefer to use madspin, can I achieve what I expect by means of "generate p p > z v j j QCD=0 SMHLOOP=0 NP=1" (with v=z,w+,w-) in the proc_card, then decay vector bosons using a madspin_card and finally performing a reweighting procedure (by using a customizecards and a reweight_card).
I am already using reweighting procedure on event analysis performed on lhe outputs. Could it be a correct workaround?

Many thanks,

Riccardo

Hi,

If this is good enough then the option of putting the constraint within madspin should work as well since the difference between your method and madspin is that madspin unweight the sample.

You can do that yes but it sounds much better to use the decay syntax in this case. But I likely miss a point.

Cheers,

Olivier

> On 16 Dec 2020, at 16:55, Riccardo <email address hidden> wrote:
>
> Question #694542 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/694542
>
> Status: Answered => Open
>
> Riccardo is still having a problem:
> Dear Olivier,
>
> If I prefer to use madspin, can I achieve what I expect by means of "generate p p > z v j j QCD=0 SMHLOOP=0 NP=1" (with v=z,w+,w-) in the proc_card, then decay vector bosons using a madspin_card and finally performing a reweighting procedure (by using a customizecards and a reweight_card).
> I am already using reweighting procedure on event analysis performed on lhe outputs. Could it be a correct workaround?
>
> Many thanks,
>
> Riccardo
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.