Neutrino Propagation through a Fluctuating

We summarize a general formulation of particle propagation in fluctuating media, as applied to the description of neutrino propagation through the sun. It contains the familiar MSW effective hamiltonian, plus corrections which describe neutrino interactions with fluctuations in the medium. An estimate of the size of these corrections for a simple model of solar fluctuations is made, with the conclusion that they can produce surprisingly large effects since they grow with the correlation length of the fluctuation. For MSW oscillations, the leading effect for small fluctuations is to diminish the quality of the resonance, making the suppression of the 7 Be neutrinos an experimental probe of fluctuations deep within the sun. Fluctuations can also provide an energy-independent suppression factor of 1 2 , away from the resonant region, even for small vacuum mixing angles. To be even potentially detectable, density fluctuations must be correlated on scales of hundreds of kilometres, and have amplitudes of a few percent or larger. The next generation of solar-neutrino detectors, including SNO and Super Kamiokande, 1 bring us into a new era, in which neutrino solutions to the solar-neutrino problem will be put under detailed experimental scrutiny. It therefore behooves theorists to understand in detail the corrections to the predictions of standard solar models, with and without neutrino oscillations. Since standard treatments 2 of MSW oscillations replace the solar medium with an average electron density , one such correction consists of how fluctuations in solar properties about this average can affect neutrino propagation. We very briefly review here a method 3 for treating such fluctuations systematically. Limitations of space preclude our discussing related approaches 4,5 to these issues.