Abstract

We present new constraints on the neutrino oscillation parameters $\Delta m^2_21$, $þeta_12$, and $þeta_13$ from a three-flavor analysis of solar and KamLAND data. The KamLAND data set includes data acquired following a radiopurity upgrade and amounts to a total exposure of $3.49 10^32$ target-proton-year. Under the assumption of CPT invariance, a two-flavor analysis ($þeta_13 = 0$) of the KamLAND and solar data yields the best-fit values $\tan^2 þeta_12 = 0.444^+0.036_-0.030$ and $\Delta m^2_21 = 7.50^+0.19_-0.20 10^-5 ~ eV^2$; a three-flavor analysis with $þeta_13$ as a free parameter yields the best-fit values $\tan^2 þeta_12 = 0.452^+0.035_-0.033$, $\Delta m^2_21 = 7.50^+0.19_-0.20 10^-5 ~ eV^2$, and $\sin^2 þeta_13 = 0.020^+0.016_-0.016$. This $þeta_13$ interval is consistent with other recent work combining the CHOOZ, atmospheric and long-baseline accelerator experiments. We also present a new global $þeta_13$ analysis, incorporating the CHOOZ, atmospheric and accelerator data, which indicates $\sin^2 þeta_13 = 0.017^+0.010_-0.009$, a nonzero value at the 93% C.L. This finding will be further tested by upcoming accelerator and reactor experiments.

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