Hints on the seesaw mechanism from the neutrino spectrum 
			 Alberto Casas
				UAM, Madrid
			
			Mercredi 17/01/2007, 14:15
			Salle Claude Itzykson, Bât. 774, Orme des Merisiers
			It is an experimental fact that the mass ratio for the two heavier neutrinos, $h = m_3/m_2 < 6$, is much smaller than the typical quark and lepton hierarchies, which are of order (20-300). We explore whether this peculiar pattern of neutrino masses can be a consequence of the peculiar way they are generated through a see-saw mechanism.