madspin of NLO process decay

Dear Tim,

> If I want the decay modes of h > a a, h > WW* and h > ZZ*, how can I do ?

for h > a a
It is technically possible, but for this you need to have a mode which include h > a a at tree level.
You can either generate tt~h directly in such model (The HC model is able to run at NLO)
or ask MadSpin to change the model when running that program (in such case you can use the built-in model heft).
See https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/MadSpin#Fulllistofoptions for details.

For h > WW and/or h > ZZ, This is not possible with standard MadSpin (only two body decay are allowed),
One possibility is to deactivate the spin-correlation/ breit-wigner smearing.
“set spinmode none” which allows to have N body decay.
(since the Higgs is a scalar with a very small width this is actually not a problem)
Obviously in that mode, it is equivalent of making the decay directly in Pythia.

> The other problem is could I use Delphes or PGS to analyse NLO events ?

We do not have the interface for that.
PGS is not compatible at all (can not handle negative weight) but Delphes should not have any problem.

Cheers,

Olivier

On 28 Aug 2015, at 11:21, Tim Lu <email address hidden> wrote:

> New question #270858 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/270858
>
> Dear experts,
>
> I have a problem about madspin of NLO process decay :
> For example, when I generate a process of p p > t t~ h
> then use madspin to decay higgs, what we can choose are h > b b~ & h > ta+ ta-
> If I want the decay modes of h > a a, h > WW* and h > ZZ*, how can I do ?
> If I can not use madspin for h > a a, h > WW* and h > ZZ* decay modes, could I have other methods to deal with that ?
>
> The other problem is could I use Delphes or PGS to analyze NLO events ?
> I have already installed both Delphes and PGS, but when I run MG5_aMC@NLO, I can not choose them...
>
> Thank you very much ! !
>
> Best,
> Tim
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Dear Olivier,

Thanks a lot for your answer !
But I still have some problems about your answer :
First, could I use PYTHIA or HERWIG to deal with h > a a, h > WW* and h > ZZ* for NLO processes ?
If so, how should I do ? (Sorry, I am not familiar with the detail of PYTHIA or HERWIG...
and what is the difference from the MadSpin and PYTHIA or HERWIG for the decay modes ?

Second, if I want to use Delphes to analyze NLO events, how should I do ?
Do I need to use two steps to deal with that ?

Thanks again !

Best,
Tim

Thanks Olivier Mattelaer, that solved my question.