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Phys Rev Lett. 2008 Jun 6;100(22):221803. Epub 2008 Jun 5.

Precision measurement of neutrino oscillation parameters with KamLAND.

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Research Center for Neutrino Science, Tohoku University, Sendai 980-8578, Japan.

Erratum in

  • Phys Rev Lett. 2008 Sep 12;101(11):119904.
  • Phys Rev Lett. 2008 Dec 19;101(25):259901.


The KamLAND experiment has determined a precise value for the neutrino oscillation parameter Deltam21(2) and stringent constraints on theta12. The exposure to nuclear reactor antineutrinos is increased almost fourfold over previous results to 2.44 x 10(32) proton yr due to longer livetime and an enlarged fiducial volume. An undistorted reactor nu[over]e energy spectrum is now rejected at >5sigma. Analysis of the reactor spectrum above the inverse beta decay energy threshold, and including geoneutrinos, gives a best fit at Deltam21(2)=7.58(-0.13)(+0.14)(stat) -0.15+0.15(syst) x 10(-5) eV2 and tan2theta12=0.56(-0.07)+0.10(stat) -0.06+0.10(syst). Local Deltachi2 minima at higher and lower Deltam21(2) are disfavored at >4sigma. Combining with solar neutrino data, we obtain Deltam21(2)=7.59(-0.21)+0.21 x 10(-5) eV2 and tan2theta12=0.47(-0.05)+0.06.

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