HC model NLO with decay

Hi,

I do not see any easy solution in version 2.2.3.

But it is likely that the next version 2.3 will allow new option in madspin.
Including a mode without full-spin correlation (“set spin mode none”) in that mode you will be able to have decay in arbitrary number of particle.
For spin 0, they are no spin correlation and this is therefore fully valid for what you want do do.

Cheers,

Olivier

On 19 Mar 2015, at 19:46, Adam Kaluza <email address hidden> wrote:

> New question #263854 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/263854
>
> Dear MadGraph team,
>
> I need to generate the process p p > x0 j j, x0 > w+ w- > l+ vl l- vl~ in NLO with the HC_NLO_X0 model. What would be the best way if possible? So far I'm getting errors:
>
> MG5_aMC>generate p p > x0 j j [QCD] , x0 > w+ w- > l+ vl l- vl~
> InvalidCmd : ML5 cannot yet decay a core process including loop corrections.
>
> MG5_aMC>generate p p > x0 j j > l+ vl l- vl~ j j [QCD]
> Command "generate p p > x0 j j > l+ vl l- vl~ j j [QCD]" interrupted with error:
> InvalidCmd : Born diagrams could not be generated for the process: g/u/c/d/s/u~/c~/d~/s~ g/u/c/d/s/u~/c~/d~/s~ > x0 g u c d s u~ c~ d~ s~> e+/mu+ ve/vm/vt e-/mu- ve~/vm~/vt~ g/u/c/d/s/u~/c~/d~/s~ g/u/c/d/s/u~/c~/d~/s~ QNP=1 WEIGHTED=24 XGLU=1 [ all = QCD ]. Notice that aMC@NLO does not handle loop-induced processes yet, but you can still use MadLoop if you want to only generate them. For this, use the 'virt=' mode, without multiparticle labels.
>
> The production p p > x0 j j [QCD] is possible in NLO and I read that with madspin you can do decays afterwards, but unfortunately my x0 has a mass of 125GeV and one of the W's need to be offshell which is not possible with madspn, right?
> Do you have any solution?
>
> Thanks you in advance!
>
> Cheers,
> Adam
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Dear Adam,

Let me add the following to Olivier's answer.

Actually, because the x0 is a (pseudo)-scalar particle, there is no need to decay it at the level of the matrix elements: there are no spin correlations between production and decay. You might as well generate p p > x0 j j [QCD] and let the parton shower do the decays.

Hope this helps.

Best,
Rikkert

Hi Rik,

I was always reluctant to do that, since you have a spin-correlation effect in the Higgs decay.
Since this is a very important channel it is likely that all parton-shower program are able to
simulate such decay correctly, but are you sure that all the parton shower code include that effect?

Cheers,

Olivier

On 20 Mar 2015, at 04:31, Rikkert Frederix <email address hidden> wrote:

> Question #263854 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/263854
>
> Rikkert Frederix proposed the following answer:
> Dear Adam,
>
> Let me add the following to Olivier's answer.
>
> Actually, because the x0 is a (pseudo)-scalar particle, there is no need
> to decay it at the level of the matrix elements: there are no spin
> correlations between production and decay. You might as well generate p
> p > x0 j j [QCD] and let the parton shower do the decays.
>
> Hope this helps.
>
> Best,
> Rikkert
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

The Higgs decays are so important that they are all correctly implemented in all parton showers. Probably, also most SUSY decays are in there. For more exotic stuff, this is probably not the case.

Cheers,
Rikkert

Hi Olivier, Rikkert,

thank you for your help!

To the parton shower: I'm not very confident that the parton shower will give me correct results, since the HC model includes higher dimensional operators in the lagrangian which result in effects also in the decay of the Higgs. For example the HWW branching ratio could be different and also there will be effects on the kinematics of the leptons and neutrinos which are not SM like. Please correct me if I'm wrong, I don't know a lot about parton showering.

Speaking of that, if I wait for the 2.3 version of MadGraph, is MadSpin able to handle the anomalous HWW coupling in general with the “set spin mode none” option?

Thanks,
Adam

Hi,

> Speaking of that, if I wait for the 2.3 version of MadGraph, is MadSpin
> able to handle the anomalous HWW coupling in general with the “set spinmode none” option?

Yes it will be.

Cheers,

Olivier

On 20 Mar 2015, at 22:21, Adam Kaluza <email address hidden> wrote:

> Question #263854 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/263854
>
> Status: Answered => Open
>
> Adam Kaluza is still having a problem:
> Hi Olivier, Rikkert,
>
> thank you for your help!
>
> To the parton shower: I'm not very confident that the parton shower will
> give me correct results, since the HC model includes higher dimensional
> operators in the lagrangian which result in effects also in the decay of
> the Higgs. For example the HWW branching ratio could be different and
> also there will be effects on the kinematics of the leptons and
> neutrinos which are not SM like. Please correct me if I'm wrong, I don't
> know a lot about parton showering.
>
> Speaking of that, if I wait for the 2.3 version of MadGraph, is MadSpin
> able to handle the anomalous HWW coupling in general with the “set spin
> mode none” option?
>
> Thanks,
> Adam
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.