Neutrinos propagating in media (matter and electromagnetic fields) undergo flavor and helicity oscillations, where helicity transitions are instigated both by electromagnetic fields and matter currents. In addition, it has been shown that correlation
s between neutrinos and antineutrinos of opposite momentum can build up in anisotropic media. We re-derive the neutrino equations of motion in the mean-field approximation for homogeneous yet anisotropic media, confirming previous results except for a small correction in the Majorana case. Furthermore, we derive the mean-field Hamiltonian induced by neutrino electromagnetic interactions. We also provide a phenomenological discussion of pair correlations in comparison with helicity correlations.
The radiative decay of sterile neutrinos with typical masses of 10 keV is investigated in the presence of a strong magnetic field and degenerate plasma. Full account is taken of the strongly modified photon dispersion relation relative to vacuum. The
limiting cases of relativistic and non-relativistic plasma are analyzed. The decay rate in a strongly magnetized plasma as a function of the electron number density is compared with the un-magnetized case. We find that a strong magnetic field suppresses the catalyzing influence of the plasma on the decay rate.
In scintillator detectors, the forward displacement of the neutron in the reaction $bar u_e+pto e^++n$ provides neutrino directional information as demonstrated by the CHOOZ reactor experiment with 2,500 events. The near detector of the forthcoming D
ouble Chooz experiment will collect $1.6times10^5$ events per year, enough to determine the average neutrino direction with a $1 sigma$ half-cone aperture of $2.3^circ$ in one year. It is more difficult to separate the two Chooz reactors that are viewed at a separation angle $phi=30^circ$. If their strengths are known and approximately equal, the azimuthal location of each reactor is obtained with $pm6^circ$ ($1 sigma$) and the probability of confusing them with a single source is less than 11%. Five years data reduce this ``confusion probability to less than 0.3%, i.e., a $3 sigma$ separation is possible. All of these numbers improve rapidly with increasing angular separation of the sources. For a setup with $phi=90^circ$ and one years data, the azimuthal $1 sigma$ uncertainty for each source decreases to $pm3.2^circ$. Of course, for Double Chooz the two reactor locations are known, allowing one instead to measure their individual one-year integrated power output to $pm11%$ ($1 sigma$), and their five-year integrated output to $pm4.8%$ ($1 sigma$).
