MadSpin bug when deciding which particles need BR+width recalculation

[Emanuele Usai]

Dear MadGraph Experts,

I am trying to use "unphysical" branching ratios in MadSpin (that is, disregarding the values obtained from the coupling parameters) by setting custom BR values in the param card below a DECAY statement for a given particle.

However I found this little bug: if the MadSpin card contains a decay statement with a multi-particle definition, then MS doesn't recognize the branching fractions in the param card coming from the particles contained in the multi-particle define.

One possible solution is in the attached patch, to be applied against [1].

Cheers,
Emanuele

[1] https://code.launchpad.net/~maddevelopers/mg5amcnlo/MS_fix_bug

[Olivier Mattelaer (olivier-mattelaer)]

Dear Emanuele,

Thanks a lot for this, this is wonderful.

I have apply it to our development version.

Cheers,

Olivier
On 07 Apr 2015, at 02:12, Emanuele Usai <email address hidden> wrote:

> Public bug reported:
>
> Dear MadGraph Experts,
>
> I am trying to use "unphysical" branching ratios in MadSpin (that is,
> disregarding the values obtained from the coupling parameters) by
> setting custom BR values in the param card below a DECAY statement for a
> given particle.
>
> However I found this little bug: if the MadSpin card contains a decay
> statement with a multi-particle definition, then MS doesn't recognize
> the branching fractions in the param card coming from the particles
> contained in the multi-particle define.
>
> One possible solution is in the attached patch, to be applied against
> [1].
>
> Cheers,
> Emanuele
>
> [1] https://code.launchpad.net/~maddevelopers/mg5amcnlo/MS_fix_bug
>
> ** Affects: mg5amcnlo
> Importance: Undecided
> Status: New
>
> ** Patch added: "decay.patch"
> https://bugs.launchpad.net/bugs/1440939/+attachment/4368069/+files/decay.patch
>
> --
> You received this bug notification because you are subscribed to
> MadGraph5_aMC@NLO.
> https://bugs.launchpad.net/bugs/1440939
>
> Title:
> MadSpin bug when deciding which particles need BR+width recalculation
>
> Status in MadGraph5_aMC@NLO Generator:
> New
>
> Bug description:
> Dear MadGraph Experts,
>
> I am trying to use "unphysical" branching ratios in MadSpin (that is,
> disregarding the values obtained from the coupling parameters) by
> setting custom BR values in the param card below a DECAY statement for
> a given particle.
>
> However I found this little bug: if the MadSpin card contains a decay
> statement with a multi-particle definition, then MS doesn't recognize
> the branching fractions in the param card coming from the particles
> contained in the multi-particle define.
>
> One possible solution is in the attached patch, to be applied against
> [1].
>
> Cheers,
> Emanuele
>
> [1] https://code.launchpad.net/~maddevelopers/mg5amcnlo/MS_fix_bug
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/mg5amcnlo/+bug/1440939/+subscriptions