Higgs to 2W-boson decay width

Hi Teddym,

Could you send me by email (<email address hidden>), your input_card for both case.

By looking at the analytical formula used in the online tools, I’m surprised by the power of the coupling.
It seems that the coupling is at the power 4 while I was expecting only a power 2 on it.
If I use the online calculator for the SM, then the coupling is indeed at the power 2 and both code match as showed in the MadWidth paper: arXiv:1402.1178

If you can send me your input file, then I can change this expression to see if I have now agreement or not.

Cheers,

Olivier

On May 14, 2014, at 12:47 PM, teddym <email address hidden> wrote:

> New question #248662 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/248662
>
> Hi:
> I'm working under mssm-full model using my own generated mass-spectrum. And I used the tool on the MG5 web site to generate the parameter card. But compared to the results of MG5 itself, the parameter card generated by the tool on web has problem on higgs sector:
>
> For the parameter card generated by tools on web, the decay information of higgs is:
> ======================================================================
> # PDG Width
> DECAY 25 2.13184002E-03 # h decays
> # BR NDA ID1 ID2
> 1.25231265E-01 2 15 -15 # BR(H1 -> tau- tau+)
> 6.42745864E-01 2 5 -5 # BR(H1 -> b bb)
> 2.10401002E-01 2 24 -24 # BR(H1 -> W+ W-)
> 2.16218689E-02 2 23 23 # BR(H1 -> Z Z)
> #
> =======================================================================
>
> When I use the command " compute_widths h1 --path=xxxxx --output=******* " I get the decay information as below:
> ========================================================================
> DECAY 25 2.535610e-03 #
> 5.403951e-01 2 -5 5 # 0.00137023135691
> 1.052895e-01 2 -15 15 # 0.000266973023357
> 5.391603e-02 3 -24 -3 4 # 0.000136710036789
> 5.338359e-02 3 -4 3 24 # 0.000135359981564
> 5.330078e-02 3 -24 -1 2 # 0.000135150010286
> 5.300499e-02 3 -2 1 24 # 0.000134399999244
> 1.777600e-02 3 -24 -15 16 # 4.50730036495e-05
> 1.773912e-02 3 -12 11 24 # 4.49794975009e-05
> 1.773912e-02 3 -14 13 24 # 4.49794975009e-05
> 1.769357e-02 3 -24 -11 12 # 4.48639956236e-05
> 1.769357e-02 3 -24 -13 14 # 4.48639956236e-05
> 1.766951e-02 3 -16 15 24 # 4.48030014418e-05
> 5.792863e-03 2 1000022 1000022 # 1.46884441759e-05
> 4.452972e-03 3 -1 1 23 # 1.12910022194e-05
> 4.452972e-03 3 -3 3 23 # 1.12910022194e-05
> 3.517377e-03 3 -5 5 23 # 8.91869793938e-06
> 3.482199e-03 3 -2 2 23 # 8.82949991351e-06
> 3.482199e-03 3 -4 4 23 # 8.82949991351e-06
> 2.057887e-03 3 -12 12 23 # 5.21800011794e-06
> 2.057887e-03 3 -14 14 23 # 5.21800011794e-06
> 2.057887e-03 3 -16 16 23 # 5.21800011794e-06
> 1.028963e-03 3 -11 11 23 # 2.60905043087e-06
> 1.028963e-03 3 -13 13 23 # 2.60905043087e-06
> 9.870209e-04 3 -15 15 23 # 2.50270033204e-06
> ==================================================================
>
> For the channel h -> b b and h-> tau tau, these two methods match well. However for the h->WW* and h->ZZ*, the results of the MG5 is almost 2 times the results from the tool on web.
>
> So which should I trust? And which results of decay information of h->WW* should I use for further estimation?
>
> Thanks
>
>
> Teddy
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Actually,

I think that the number are different and they can actually be BOTH correct.
The difference is that one return a branching ratio for H > WW*
While the second return a branching ration for H > W q1 q2
If you look at the diagram used for the computation of the second, you will see that the H > W W contributes but that some other diagram contributes to the same final state (in this case the charged Higgs can replace the W).

Now, I'm always confuse how you can define a Branching ratio for H> W W since the branching ratio is define in the Narrow Width Approximation which does not hold in this case. This is actually even worse in this case since you can't distinguish between the charged Higgs and the W+ since None of them are on-shell. So I will personally trust better the value returned by MadWidth.

Cheers,

Olivier

Hi:
    Thanks for your reply.
    I'm also confused with the Branching ratio for H->WW* ( also H->ZZ*).
    So, actually, I should trust the result from MG.
   Then, If the result from online mssm calculator is not the same as that from MG, when I use the card from online calculator as input param_card, does it affect the calculation of MG5 for some processes involving h1->W+W->j j l vl ?

Best

Teddy

Hi Teddy,

The partial width/Branching ration are not use for the computation of the cross-section/generation of events.
Only the total width is an input of the computation, so this does not matter at all.
On the other hand Pythia/Herwig use those for decaying those particles but since you decay them in MG it does not matter either.

Now be careful since the Higss has some non trivial/negligible loop induce decay which are not include by the command that you use in MG.
(in particular the decay in 2 gluon). So your total width is under-evaluated.This doesn’t change anything for the kinematics but change the cross-section.

Cheers,

Olivier

On May 15, 2014, at 3:47 AM, teddym <email address hidden> wrote:

> Question #248662 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/248662
>
> Status: Answered => Open
>
> teddym is still having a problem:
> Hi:
> Thanks for your reply.
> I'm also confused with the Branching ratio for H->WW* ( also H->ZZ*).
> So, actually, I should trust the result from MG.
> Then, If the result from online mssm calculator is not the same as that from MG, when I use the card from online calculator as input param_card, does it affect the calculation of MG5 for some processes involving h1->W+W->j j l vl ?
>
>
> Best
>
> Teddy
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.