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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