  We can start with the question: why are neutrino properties especially
interesting? Recall that in the minimal standard model there are no right
handed neutrinos and furthermore lepton number is conserved so neutrinos can
have neither Dirac nor Majorana masses. Furthermore, with zero masses, the
mixing angles in the charged weak current are all zero. Any evidence for
non-zero masses or mixing angles is evidence for physics beyond the standard
model and hence potentially a powerful tool. Besides, the masses and mixing
angles are fundamental parameters which will have to be explained by the
eventual theory of fermion masses.
