We consider possibilities of observing T-violation effects in neutrino oscillation experiments with a very long baseline $\left(\sim 10000\hspace{0.5em}\mathrm{km}\right)$ using a low energy neutrino $(\sim$ several hundreds MeV). We show that the matter effect effectively changes only the first-second generation mixing angle, respecting solar neutrino deficits and atmospheric neutrino anomalies. The effective mixing of the first-second generation in the Earth grows up to maximum by resonance. This effect enables one to search T-violation in case the first-second mixing angle is small. We discuss its implications to the observations of T-violation effects in long baseline experiments.

• Received 5 November 1999

DOI:https://doi.org/10.1103/PhysRevD.62.073006