MadGraph5_aMC@NLO

spin information when using s-channel syntax

Asked by Meng Lu

Dear Experts,

when using syntax like "p p > z > e+ e-", it seems the spin information of "z" is not in the LHEF, do I understand it correctly. The reason why I ask is I try to produce polarized diboson events from loop process, i.e., " g g > w+{0} w-{0} $$h [noborn=QCD]", but neither decay chain nor madspin is supported to decay the W boson with spin correlation. So i try to use "generate g g > w+ w- > e+ e- vl vl~ $$ h [noborn=QCD]" and separate the LHE files.

If the spin information is lost, is there an alternative way for that purpose, maybe use "DECAY" package but it seems it's no longer available for download.

Cheers, Meng

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Olivier Mattelaer
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Best Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

We are starting a project to make madspin compatible with loop-induced decay, This should solve such issue. but this is not ready yet.

Concerning the intermediate particle, we do not have access to their polarization since we use the full (and standard) propagator (which is the sum over all polarization including interference term between polarization for the off-shell part of the propagator).

Cheers,

Olivier

> On 27 Sep 2023, at 20:40, Meng Lu <email address hidden> wrote:
>
> New question #708062 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/708062
>
> Dear Experts,
>
> when using syntax like "p p > z > e+ e-", it seems the spin information of "z" is not in the LHEF, do I understand it correctly. The reason why I ask is I try to produce polarized diboson events from loop process, i.e., " g g > w+{0} w-{0} $$h [noborn=QCD]", but neither decay chain nor madspin is supported to decay the W boson with spin correlation. So i try to use "generate g g > w+ w- > e+ e- vl vl~ $$ h [noborn=QCD]" and separate the LHE files.
>
> If the spin information is lost, is there an alternative way for that purpose, maybe use "DECAY" package but it seems it's no longer available for download.
>
> Cheers, Meng
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Meng Lu (meng-lu) said : 		#2

Thanks Olivier Mattelaer, that solved my question.

Revision history for this message
fgjg (yjhk) said : 		#3

When it comes to s-channel syntax, ensuring accurate propainters of information is crucial. Precision in handling data helps maintain the integrity of your analysis. Thanks for highlighting this important aspect! https://propainters.ae/