PONTECORVO NEUTRINO-ANTINEUTRINO OSCILLATIONS - THEORY AND EXPERIMENTAL LIMITS

We study Pontecorvo neutrino-antineutrino oscillations both in vacuum and in matter within a field theoretic approach, showing that this phe nomenon can occur only if neutrinos have a Dirac-Majorana mass term. W e find that matter effects suppress these oscillations and cannot expl ain the solar neutrino problem. On the contrary, a vacuum neutrino-ant ineutrino oscillations solution to this problem exists. We analyze thi s solution and the available data from laboratory experiments giving s tringent limits on nu(e) and nu(mu) Majorana masses.