tau width

Hi,

The paper is the following one:
http://arxiv.org/pdf/1402.1178.pdf

The tau width is actually one of the example where our code is likely to fail.
The point is that the tau do not decay in quark but in pion (most of the time three) simply because QCD is not perturbative at the scale of the tau mass.
We have security to prevent to quote hadronic decay which are lower than the QCD scale in order to not quote a meaningless number.
In the standard model, you need to use the taudecay_UFO (typically use bias the command add model taudecay_UFO) in order to have meaningful computation of the tau width.
That Effective model introduces new particle in the model (rho/pion/…) and implements the effective theory associated to the tau decay.

Now for your exotic model, this is clearly even more tricky since I have no idea if it makes sense to merge your model with that plugin model (depends of your model).
If you want more information about that model, you can read the associate paper: arXiv:1212.6247

Cheers,

Olivier

On 08 May 2015, at 17:36, A.Hayreter <email address hidden> wrote:

> New question #266675 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/266675
>
> Dear MG5 experts,
>
> I am working on an effective Lagrangian in which tau decays are infected by new physics contributions. So the calculation of tau width is crucial in my case. When I set tau width as AUTO I can see that at the param_card.dat file tau width and fractions are listed. As far as I know MG5 auto-calculates the width on the fly by using the analytic formula given by FR. However, according to the list in param_card it looks like only leptonic modes are included in the calculation. So I like to learn how the tau width is calculated on the fly exactly and why hadronic modes are not included in the list?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Thanks Olivier, I see what you mean.