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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

Time dependence of the observed and expected reactor event rates.
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Related In: Results  -  Collection


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f5-83_027: Time dependence of the observed and expected reactor event rates.

Mentions: Background events passing through the above event-selection criteria and thus embedding inside the inverse β-decay candidates come dominantly from the reactions of 13C(α, n)16O* and 12C(n,n′)12C* induced by α particles of the radon daughter 210Po in the liquid scintillator. The μ-induced spallation-products of 9Li/8He emit a β and a neutron, thus mimicking the inverse β-decay events. Contributions from the accidental backgrounds and fast neutrons are small. Table 1 summarizes the number of the observed ν̄e candidate-events, the number of the expected reactor ν̄e events and the number of the expected background events for ANA-I and ANA-II. This table also shows the ratio of the observed ν̄e events minus background events to the expected reactor events. This ratio is 0.611 ± 0.085(stat) ± 0.041(syst) for ANA-I, and 0.658 ± 0.044(stat) ± 0.047(syst) for ANA-II. Kam-LAND observed the first evidence for reactor antineutrino disappearance with 99.95% C.L. in ANA-I and reconfirmed it with 99.998% C.L. in ANA-II. The time variations of the observed and expected reactor ν̄e event rates are plotted at the 6 data-taking-time-periods in Fig. 5. The rate of reactor antineutrino disappearance is almost constant in each time-interval.


Antineutrino science by KamLAND.

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

Time dependence of the observed and expected reactor event rates.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5-83_027: Time dependence of the observed and expected reactor event rates.
Mentions: Background events passing through the above event-selection criteria and thus embedding inside the inverse β-decay candidates come dominantly from the reactions of 13C(α, n)16O* and 12C(n,n′)12C* induced by α particles of the radon daughter 210Po in the liquid scintillator. The μ-induced spallation-products of 9Li/8He emit a β and a neutron, thus mimicking the inverse β-decay events. Contributions from the accidental backgrounds and fast neutrons are small. Table 1 summarizes the number of the observed ν̄e candidate-events, the number of the expected reactor ν̄e events and the number of the expected background events for ANA-I and ANA-II. This table also shows the ratio of the observed ν̄e events minus background events to the expected reactor events. This ratio is 0.611 ± 0.085(stat) ± 0.041(syst) for ANA-I, and 0.658 ± 0.044(stat) ± 0.047(syst) for ANA-II. Kam-LAND observed the first evidence for reactor antineutrino disappearance with 99.95% C.L. in ANA-I and reconfirmed it with 99.998% C.L. in ANA-II. The time variations of the observed and expected reactor ν̄e event rates are plotted at the 6 data-taking-time-periods in Fig. 5. The rate of reactor antineutrino disappearance is almost constant in each time-interval.

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