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Antineutrino science by KamLAND.

Suzuki A - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2007)

Bottom Line: KamLAND measured the ν̄ e's flux from distant nuclear reactors, and found fewer events than expected from standard assumptions about ν̄ e propagation at the 99.998% confidence level (C.L.).The total observed number of 4.5 to 54.2, assuming a Th/U mass concentration ratio of 3.9 is consistent with 19 predicted by geophysical models.This detection allows better estimation of the abundances and distributions of radioactive elements in the Earth, and of the Earth's overall heat budget.

View Article: PubMed Central - PubMed

Affiliation: Director General, High Energy Accelerator Research Organization, Ibaraki, Japan . ; Director General, High Energy Accelerator Research Organization, Ibaraki, Japan .

ABSTRACT
KamLAND measured the ν̄ e's flux from distant nuclear reactors, and found fewer events than expected from standard assumptions about ν̄ e propagation at the 99.998% confidence level (C.L.). The observed energy spectrum disagrees with the expected spectral shape at 99.6% C.L., and prefers the distortion from neutrino oscillation effects. A two-flavor oscillation analysis of the data from KamLAND and solar neutrino experiments with CPT invariance, yields [Formula: see text] eV(2) and [Formula: see text]. All solutions to the solar neutrino problem except for the large mixing angle (LMA) region are excluded. KamLAND succeeded in detecting geoneutrinos produced by the decays of (238)U and (232)Th within the Earth. The total observed number of 4.5 to 54.2, assuming a Th/U mass concentration ratio of 3.9 is consistent with 19 predicted by geophysical models. This detection allows better estimation of the abundances and distributions of radioactive elements in the Earth, and of the Earth's overall heat budget.

No MeSH data available.


Related in: MedlinePlus

Prompt energy spectrum of ν̄e candidate events with associated background spectra. The no-oscillation, the best-fit scaled no-oscillation and the best-fit oscillation spectra are compared to the data.
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f6-83_027: Prompt energy spectrum of ν̄e candidate events with associated background spectra. The no-oscillation, the best-fit scaled no-oscillation and the best-fit oscillation spectra are compared to the data.

Mentions: The prompt energy spectrum above 2.6 MeV is shown in Fig. 6, comparing with the spectra estimated from the reactor ν̄e events, and the accidental and 13C(α, n)16O backgrounds. The observation definitely deviates from the reactor neutrino shape in the energy below 4 MeV. Even in making the normalization free, the best fit of the scaled reactor spectrum shown also in Fig. 6 disagrees with the observation, being excluded at the 99.6% C.L. Here the spectral distortion due to the systematic uncertainties for the backgrounds is considered in the following: for the 13C(α, n)16O background, a free-scale uncertainty around 6 MeV and a 32% scale uncertainty of the estimated rate around 2.6 and 4.4 MeV are applied to fitting. KamLAND gives the first evidence of the spectrum distortion in neutrino experiments with the confidence level of ∼ 3σ. The reactor neutrino anomaly defined as the combined effect of the rate disappearance and spectrum distortion is found at the high confidence level of 99.999995%.


Antineutrino science by KamLAND.

Suzuki A - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2007)

Prompt energy spectrum of ν̄e candidate events with associated background spectra. The no-oscillation, the best-fit scaled no-oscillation and the best-fit oscillation spectra are compared to the data.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756737&req=5

f6-83_027: Prompt energy spectrum of ν̄e candidate events with associated background spectra. The no-oscillation, the best-fit scaled no-oscillation and the best-fit oscillation spectra are compared to the data.
Mentions: The prompt energy spectrum above 2.6 MeV is shown in Fig. 6, comparing with the spectra estimated from the reactor ν̄e events, and the accidental and 13C(α, n)16O backgrounds. The observation definitely deviates from the reactor neutrino shape in the energy below 4 MeV. Even in making the normalization free, the best fit of the scaled reactor spectrum shown also in Fig. 6 disagrees with the observation, being excluded at the 99.6% C.L. Here the spectral distortion due to the systematic uncertainties for the backgrounds is considered in the following: for the 13C(α, n)16O background, a free-scale uncertainty around 6 MeV and a 32% scale uncertainty of the estimated rate around 2.6 and 4.4 MeV are applied to fitting. KamLAND gives the first evidence of the spectrum distortion in neutrino experiments with the confidence level of ∼ 3σ. The reactor neutrino anomaly defined as the combined effect of the rate disappearance and spectrum distortion is found at the high confidence level of 99.999995%.

Bottom Line: KamLAND measured the ν̄ e's flux from distant nuclear reactors, and found fewer events than expected from standard assumptions about ν̄ e propagation at the 99.998% confidence level (C.L.).The total observed number of 4.5 to 54.2, assuming a Th/U mass concentration ratio of 3.9 is consistent with 19 predicted by geophysical models.This detection allows better estimation of the abundances and distributions of radioactive elements in the Earth, and of the Earth's overall heat budget.

View Article: PubMed Central - PubMed

Affiliation: Director General, High Energy Accelerator Research Organization, Ibaraki, Japan . ; Director General, High Energy Accelerator Research Organization, Ibaraki, Japan .

ABSTRACT
KamLAND measured the ν̄ e's flux from distant nuclear reactors, and found fewer events than expected from standard assumptions about ν̄ e propagation at the 99.998% confidence level (C.L.). The observed energy spectrum disagrees with the expected spectral shape at 99.6% C.L., and prefers the distortion from neutrino oscillation effects. A two-flavor oscillation analysis of the data from KamLAND and solar neutrino experiments with CPT invariance, yields [Formula: see text] eV(2) and [Formula: see text]. All solutions to the solar neutrino problem except for the large mixing angle (LMA) region are excluded. KamLAND succeeded in detecting geoneutrinos produced by the decays of (238)U and (232)Th within the Earth. The total observed number of 4.5 to 54.2, assuming a Th/U mass concentration ratio of 3.9 is consistent with 19 predicted by geophysical models. This detection allows better estimation of the abundances and distributions of radioactive elements in the Earth, and of the Earth's overall heat budget.

No MeSH data available.


Related in: MedlinePlus