modifying Br in MadSpin

Yes,

By default the BR are computed automatically (on the flight) at LO accuracy (and only 2 body).
If you prefer another precision, you can/have to specify the value of the BR in the param_card.dat that you use to generate events.

If you are not sure of the format, just run once with the width set to “Auto”, and the param_card will be replace with the new one containing the BR information read by MadSpin.

Cheers,

Olivier

On 27 Jul 2015, at 23:26, Valerio Dao <email address hidden> wrote:

> New question #269715 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/269715
>
> Hello,
>
> I assume that this is a rather trivial question but I wasn't able to find the answer in the documentation.
>
> I manage to use MadSpin to decay the W boson in some NLO production.
> Nevertheless I see in the log that the Br used are:
>
> generate 00:05:05 INFO: decay channels for w- : ( width = 2.0463 GeV )
> generate 00:05:05 INFO: BR d1 d2
> generate 00:05:05 INFO: 3.333578e-01 d u~
> generate 00:05:05 INFO: 3.333578e-01 s c~
> generate 00:05:05 INFO: 1.111225e-01 e- ve~
> generate 00:05:05 INFO: 1.111225e-01 mu- vm~
> generate 00:05:05 INFO: 1.110394e-01 ta- vt~
> generate 00:05:05 INFO:
>
> which are slightly old w.r.t. the preferred PDG value of 0.108 ......
> Is there an easy way to modify these Br?
>
> thanks a lot,
>
> Valerio
>
>
>
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