Reading and setting decay width values

Hi Spyros,

> There are 2 input sources: the param_card*.dat under Template/(N)LO/Cards (around line #60) and restrict*.dat under models/
> Apparently when aMC@NLO runs, the values that are transferred in MYPROC/Cards/param_card.dat are the ones from the restrict*.dat cards and not from Template/NLO/Cards/param_card.dat. The value from restrict*.dat is also the one which seems to be used for the partial widths calculation in MadSpin.
> As a result it seems that if we want to change a decay width for all possible models, we would need to make the change in multiple files. Is this correct?

Yes you are right.

> A different but related question is if (and how) we can manually set a partial width (or BR) to be used in MadSpin.

If in your param_card you have the information about the partial width (i.e. the following one) then MS will use the information from the
param_card and will not compute the width/partial width on the flight.

DECAY 23 2.441755e+00
# BR NDA ID1 ID2 ...
   1.523651e-01 2 3 -3 # 0.372038381506
   1.523651e-01 2 1 -1 # 0.372038381506
   1.507430e-01 2 5 -5 # 0.368077510282
   1.188151e-01 2 4 -4 # 0.290117391009
   1.188151e-01 2 2 -2 # 0.290117391009
   6.793735e-02 2 16 -16 # 0.165886384843
   6.793735e-02 2 14 -14 # 0.165886384843
   6.793735e-02 2 12 -12 # 0.165886384843
   3.438731e-02 2 13 -13 # 0.0839653943458
   3.438731e-02 2 11 -11 # 0.0839653943458
   3.430994e-02 2 15 -15 # 0.0837764784469

Cheers,

Olivier

On Aug 5, 2013, at 8:31 AM, Spyridon Argyropoulos <email address hidden> wrote:

> New question #233563 on MadGraph5:
> https://answers.launchpad.net/madgraph5/+question/233563
>
> Dear all,
>
> I was wondering where the values from the decay widths are read from.
> I am interested mainly in the aMC@NLO case, but I guess MadGraph would work the same way.
>
> There are 2 input sources: the param_card*.dat under Template/(N)LO/Cards (around line #60) and restrict*.dat under models/
> Apparently when aMC@NLO runs, the values that are transferred in MYPROC/Cards/param_card.dat are the ones from the restrict*.dat cards and not from Template/NLO/Cards/param_card.dat. The value from restrict*.dat is also the one which seems to be used for the partial widths calculation in MadSpin.
> As a result it seems that if we want to change a decay width for all possible models, we would need to make the change in multiple files. Is this correct?
>
> A different but related question is if (and how) we can manually set a partial width (or BR) to be used in MadSpin.
>
> Thanks and best regards,
> Spyros
>
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