Comment 1 for bug 1805107

Hi,

The warning is actually an Information and not a warning (it is not even quoted as a warning actually). It just means that MadSpin is going to drop some events in order to keep the correct relative abondance of each subprocess in your sample.
Since number are quite close in your case, the number of events dropped should be quite small.

> Madspin gets stuck decaying the events:

This typically means that the un-weighting efficiency of the process is quite bad. The typical reason is that narrow-width approximation does not hold for that benchmark point, leading to theoretical trouble and issue in the Madspin method.

If you are running at LO, you have the possibility of not using MadSpin and to use the decay-chain syntax. (like p p > t t~, (t > w+ b, w+ > l+ vl), (t~ > w- b~, w-> j j ).
You can generate your process like this to test if this goes smoothly and if your NWA seems to work or not (that syntax is also based on NWA, but the cross-section is not computed assuming NWA.

Cheers,

Olivier