Reported to the developers mailing list by Anke Biekoetter:
Dear EvtGen developers,
I just came across a small typo in the EvtGen default DECAY.DEC files:
The BR for B+ -> eta' l+ nu is listed as
0.000230 eta' mu- anti-nu_mu PHOTOS ISGW2;
However, it should be 2.3*10^-5 instead of 2.3*10^-4 . So there is
one zero missing there, I think.
I realized that I had quite a large eta' peak in semileptonic B->Xu l nu
decays and I think this is just a typo in the default decay card.
I just thought that you might want to update this in future versions.