For the atmospheric neutrinos, flavor changing neutral currents (FCNC) [37],
Lorentz
invariance violation (LIV), and Equivalence Principle Violation
(EPV) [38,39] models
for neutrino mixing have been suggested as alternatives to conventional
flavor mixing. However, they are not consistent with zenith
or upward throughgoing distributions. For example, LIV and EPV
predict an dependence with
, contrary to the
SuperK data.
and
refer to the distance travelled and
energy of the
, respectively. Pure
decay
models are not viable, but a hybrid oscillation and decay model with two
nearly degenerate states, the lightest decaying to sterile states, cannot be
excluded. Also, decoherence models, in which the coherence between two
states is lost by some unknown mechanism (e.g., interaction with
quantum foam), are consistent with the
data.
There are viable descriptions of the solar neutrino data involving involving
FCNC, LIV, and EPV. Another alternative is resonant
spin flavor precession (RSPF) [11,17,40],
in which is
transformed into a sterile or active right-handed state. This requires
a much larger neutrino magnetic moment
(which can be Dirac for a sterile
final state, or a Majorana transition moment for an active
or
) than is predicted by most models and
a rather large solar magnetic field. The original motivation for RSPF
for magnetic transitions was an apparent time dependence in the Homestake
data. This is no longer wanted experimentally, but time independent
magnetic effects could still be relevant for transitions occurring below the
convective zone.
can be generated by
combined magnetic and flavor-oscillation effects.