Re : di Higgs

Hi,

Doing such type of asymmetric decay is first not really physical (since the both decay should happened at the same scale)
and you might have factor of 2 wrong in the computed cross-section due to some symmetry factor missing.
See: https://bugs.launchpad.net/mg5amcnlo/+bug/1367374
for other case with the same situation.

Now if you do not care about the cross-section, I would do the following:
genererate g g > h h [QCD]

and then in the madspin_card.dat
set spinmode none
decay h > ta+ ta-
decay h > b b~

and then just remove the tau from the final lhe file.

Cheers,

Olivier

> On Jun 24, 2016, at 10:27, Shankha Banerjee <email address hidden> wrote:
>
> New question #295625 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/295625
>
> Dear experts,
>
> I have a naive query. I want to generate this process,
>
> p p > h h and want to decay one of the Higgs to b bbar and want to keep the second undecayed.
>
> Is this syntax correct :
>
> p p > h b b~ / z u d c s b u~ d~ c~ s~ b~ a w+ w- g [all= QCD]
>
> ?
>
> Thank you very much for your kind help.
>
> Best regards,
>
> Shankha.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Thanks a lot Olivier.

However, when you say remove the tau from the final lhe file, you mean manually remove all the tau lines right ?

Also, will it then be possible to shower it using pythia ?

At the end I want a situation where one Higgs is undecayed and the other decays to b b~.

Sorry for this naive query.

Thanks a lot.

Best regards,

Shankha.

Hi,

> However, when you say remove the tau from the final lhe file, you mean
> manually remove all the tau lines right ?

Basically yes, of course you need to ensure the self-consistency of all the other information
I can think of
- the number associated to the number of particle
- the mother information.
- the status information for the h

You can look at the following madgraph function:
madgraph/various/lhe_parser.py around line 1332.
they are the function remove_decay
which is doing something similar.
(but this function is not used by Madgraph so please be extra carefull if you want to use it)

> Also, will it then be possible to shower it using pythia ?

As long as you have a valid lhe at the end yes.

> At the end I want a situation where one Higgs is undecayed and the other
> decays to b b~.

I would advocate that the best is to NOT do that.
Either you do not decay them or decay them both. But decay only one sounds a terrible idea to me.

Cheers,

Olivier

> On Jun 24, 2016, at 11:02, Shankha Banerjee <email address hidden> wrote:
>
> Question #295625 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/295625
>
> Status: Answered => Open
>
> Shankha Banerjee is still having a problem:
> Thanks a lot Olivier.
>
> However, when you say remove the tau from the final lhe file, you mean
> manually remove all the tau lines right ?
>
> Also, will it then be possible to shower it using pythia ?
>
> At the end I want a situation where one Higgs is undecayed and the other
> decays to b b~.
>
> Sorry for this naive query.
>
> Thanks a lot.
>
> Best regards,
>
> Shankha.
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Dear Olivier,

Thank you very much. I will try with the option that you suggested.

Thanks.

Best regards,

Shankha.