Assumption ("qualitative" validity of SM):
All interaction are V-A (lefthanded) and all masses vanish.

---> Majorana and Weyl neutrino are completely equivalent.

Additional assumption ("quantitative" validity of SM):
The Weyl-neutrino component has quantitatively the same
weak coupling as the electron.

---> Majorana neutrinos have a sqrt(2) larger coupling strength
than the empirically observed one.