Higgs decay into Z photon

[Oscar Eboli]

Hello,

I used MadGraph to evaluate the Higgs decay width onto a Z and a photon
with the command generate h > z a [noborn=QED]. MG loaded automatically the
model loop_qcd_qed_sm. The problem was with the result that I obtained:
it is approximately half of the one reported in the literature. Did I
use MadGraph correctly? Is there a bug with this package?

Thanks,Oscar

[Hua-Sheng Shao (erdissshaw)]

Hi,

The command you used is correct. I tried myself without changing anything in the default in loop_qcd_qed_sm. I got a partial width as 6.999e-06 +- 1.906e-09 GeV for MH=125 GeV. It seems to be consistent with the one available in the twiki page of the Higgs working group (see https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageBR2014#SM_Higgs_Branching_Ratios_and_Pa). At 125 GeV, the total width is 4.07E-03 GeV and the branching ratio to Z+photon is 1.54E-03. The recommended value in LHCHXSWG is 6.27e-06. Since in the loop_sm_qcd_qed, only the LO and zero bottom Yukawa coupling are chosen (probably plus other different setup), I would say the two values are consistent.

Best, Hua-Sheng

[Oscar Eboli (oeboli)]

Dear Hua-Sheng

thanks a lot for the answer. The amazing thing is that I
obtain 3.994e-06 GeV for the h> z a partial width!
Where can I download the latest version of the
loop_qcd_qed_sm model?

thanks a lot Oscar

Em qua, 5 de set de 2018 às 09:11, Hua-Sheng Shao <email address hidden>
escreveu:

> Hi,
>
> The command you used is correct. I tried myself without changing
> anything in the default in loop_qcd_qed_sm. I got a partial width as
> 6.999e-06 +- 1.906e-09 GeV for MH=125 GeV. It seems to be consistent
> with the one available in the twiki page of the Higgs working group (see
>
> https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageBR2014#SM_Higgs_Branching_Ratios_and_Pa
> ).
> At 125 GeV, the total width is 4.07E-03 GeV and the branching ratio to
> Z+photon is 1.54E-03. The recommended value in LHCHXSWG is 6.27e-06.
> Since in the loop_sm_qcd_qed, only the LO and zero bottom Yukawa
> coupling are chosen (probably plus other different setup), I would say
> the two values are consistent.
>
> Best, Hua-Sheng
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1790545
>
> Title:
> Higgs decay into Z photon
>
> Status in MadGraph5_aMC@NLO:
> New
>
> Bug description:
> Hello,
>
> I used MadGraph to evaluate the Higgs decay width onto a Z and a photon
> with the command generate h > z a [noborn=QED]. MG loaded automatically
> the
> model loop_qcd_qed_sm. The problem was with the result that I obtained:
> it is approximately half of the one reported in the literature. Did I
> use MadGraph correctly? Is there a bug with this package?
>
> Thanks,Oscar
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/mg5amcnlo/+bug/1790545/+subscriptions
>

[Hua-Sheng Shao (erdissshaw)]

Hi Oscar,

If you are using version 2.6.1 or onwards, you just remove your original loop_qcd_qed_sm in models directory and import model in the MG5 prompt. The most up-to-date loop_qcd_qed_sm will be downloaded.

Best wishes,

Hua-Sheng

[Oscar Eboli (oeboli)]

Hi,

I was using the MG version 2.6.0. This is probably the cause of the
discrepancy.
I'm now installing the latest version.

Thanks

Em qua, 5 de set de 2018 às 10:00, Hua-Sheng Shao <email address hidden>
escreveu:

> Hi Oscar,
>
> If you are using version 2.6.1 or onwards, you just remove your original
> loop_qcd_qed_sm in models directory and import model in the MG5 prompt.
> The most up-to-date loop_qcd_qed_sm will be downloaded.
>
> Best wishes,
>
> Hua-Sheng
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1790545
>
> Title:
> Higgs decay into Z photon
>
> Status in MadGraph5_aMC@NLO:
> New
>
> Bug description:
> Hello,
>
> I used MadGraph to evaluate the Higgs decay width onto a Z and a photon
> with the command generate h > z a [noborn=QED]. MG loaded automatically
> the
> model loop_qcd_qed_sm. The problem was with the result that I obtained:
> it is approximately half of the one reported in the literature. Did I
> use MadGraph correctly? Is there a bug with this package?
>
> Thanks,Oscar
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/mg5amcnlo/+bug/1790545/+subscriptions
>