Eguchi, K (reprint author), Tohoku Univ, Res Ctr Neutrino Sci, Sendai, Miyagi 9808578, Japan.
KamLAND has measured the flux of (nu) over bar (e)'s from distant nuclear reactors. We find fewer (nu) over bar (e) events than expected from standard assumptions about (nu) over bar (e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without (nu) over bar (e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for (nu) over bar (e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded.