Neutrino masses and mixings in a seesaw framework - art. no. 097302

Assuming the seesaw mechanism for hierarchical neutrino masses, we calculat e the heavy neutrino masses under the hypotheses that the mixing in the Dir ac leptonic sector is similar to the quark mixing (V-D similar to V-CKM) an d that M(nu)similar to M-u or M-e, where M-v is the Dirac mass matrix of ne utrinos. As a result we find that for M-nu-M-u the vacuum oscillation solut ion of the solar neutrino problem leads to a scale for the heavy neutrino m ass well above the unification scale, while for the MSW solutions there is agreement with this scale. For M(nu)similar to M-e the vacuum solution is c onsistent with the unification scale and the MSW solutions with an intermed iate scale. The mass of the lightest heavy neutrino can be as small as 10(5 ) GeV.