next up previous
Next: What is needed? Up: THEORETICAL FRAMEWORK Previous: 4 neutrino schemes [,,,]

Alternatives to neutrino oscillations

Alternative explanations of the atmospheric and solar neutrino anomalies were reviewed by Lusignoli [11].

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 $LE^n$ dependence with $n \ne -1$, contrary to the SuperK data. $L$ and $E$ refer to the distance travelled and energy of the $\nu_\mu$, respectively. Pure $\nu_\mu$ 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 $\nu_{eL}$ is transformed into a sterile or active right-handed state. This requires a much larger neutrino magnetic moment $\mu_\nu$ (which can be Dirac for a sterile $N_R$ final state, or a Majorana transition moment for an active $\nu^c_{\mu R}$ or $\nu^c_{\tau R}$) 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. $\nu_{eL} \mbox{$\rightarrow$}\nu^c_{eR}$ can be generated by combined magnetic and flavor-oscillation effects.


next up previous
Next: What is needed? Up: THEORETICAL FRAMEWORK Previous: 4 neutrino schemes [,,,]
Paul Langacker 2001-09-27