A. Halprin

Effects of Light and Heavy Majorana Neutrinos in Neutrinoless Double Beta Decay

Abstract We examine interference effects between the light neutrino and the heavy neutral lepton exchange amplitudes in neutrinoless double beta [(ββ) 0 ν ] decay. Using the lower limit on the electron neutrino mass deduced from the tritium end point measurements and the most recent data on neutrinoless double beta decay of tellurium, we obtain an upper limit on the mass of the heavy neutral lepton of about 3 GeV. We also find that the effective Majorana mass parameter associated with the (ββ) 0 ν -decay exhibits a strong dependence on the parent nuclear species, and therefore searches for the (ββ) 0 ν -decay should be performed for several nuclei simultaneously and independently.

Possible violation of the equivalence principle by neutrinos.

We consider the effect of a long-range, flavor-changing tensor interaction of possible gravitational origin. Neutrino-mixing experiments provide the most sensitive probe to date for such forces{emdash}testing the equivalence principle at levels below 10{sup {minus}20}. Here we justify and generalize a formalism for describing such effects. The constraints from neutrino-mixing experiments on gravitationally induced mixing are calculated. Our detailed analysis of the atmospheric neutrino data confirms a remarkable result: the atmospheric neutrino data imply the same size violation of the equivalence principle as do the solar neutrino data. Additional tests of this suggestive result are discussed. {copyright} {ital 1996 The American Physical Society.}

Neutrino mixing due to a violation of the equivalence principle

Massless neutrinos will mix if their couplings to gravity are flavor dependent, i.e., violate the principle of equivalence. Because the gravitational interaction grows with neutrino energy, the solar neutrino problem and the recent atmospheric neutrino data may be simultaneously explained by violations at the level of 10[sup [minus]14] to 10[sup [minus]17] or smaller. This possibility is severely constrained by present accelerator neutrino experiments and will be preeminently tested in proposed long-base-line accelerator neutrino experiments.

A comment on the possibility of distinguishing between Dirac and Majorana neutrinos in νμme scattering

Abstract We demonstrate explicitly that a recent suggestion in this journal for distinguishing between Dirac and Majorana neutrinos in the standard model cannot work at the level predicted. Effects that distinguish between the two types in the ratio ν μm e→ν μm e to ν μm e → ν μm e are shown to be much too small to be addressed by accelerator experiments in the near future (unless accompanied by flavor oscillations).

SUSY partners of Majorana neutrinos in lepton number violating processes

Abstract We consider the effects of light supersymmetric partners of Majorana neutrinos in (i) neutrinoless double beta decay and (ii) muonium-antimuonium conversion together with the crossed channel ee → μμ . The first process is unaffected. The second process is dominated by the exchange of such sneutrinos and provides an amplitude two orders of magnitude greater than most previous estimates.