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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

Expected energy spectra of positrons produced by the reactor neutrinos and geoneutrinos.5)
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f3-83_027: Expected energy spectra of positrons produced by the reactor neutrinos and geoneutrinos.5)

Mentions: Upon entering the detector, ν̄e is captured by a free proton and an inverse β-decay reaction occurs, ν̄e +p → e++n. The positron deposits its energy and then annihilates, yielding two γ-rays (each 511 keV). The neutron is thermalized in (211.2 ± 2.6) μsec. and then captured by a proton in the following reaction, n + p → d + γ (2.22 MeV). Thus the inverse β-decay reaction provides a clear sequential signature of the prompt e+ and delayed γ with the definite time- and close space-correlations. The incident ν̄e energy is given by Eν ∼ Ee+ + 0.8 MeV, neglecting the small neutron recoil. Although the need to prevent any signals mimicking neutrino events is imperative, these signal correlations give a high rejection-power for background events. Nevertheless we can’t escape from the geoneutrino background. KamLAND has the first chance to search for geoneutrinos which are ν̄e’s originated from the U/Th decays inside the Earth. The radiogenic heat by the U/Th decays makes a dominant role in the energy generation of the Earth. We evaluated the detection rate of geoneutrinos in KamLAND, using various geophysical and geochemical models.5) In Fig. 3 a smooth broad histogram is the expected visible energy spectrum of positrons produced by reactor neutrinos, and 2 sharp peaks in the energy below 2.5 MeV are expected by geoneutrinos. In the reactor neutrino oscillation analysis, positrons with energies above 2.6 MeV are used to escape from the geoneutrino pollution.


Antineutrino science by KamLAND.

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

Expected energy spectra of positrons produced by the reactor neutrinos and geoneutrinos.5)
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3-83_027: Expected energy spectra of positrons produced by the reactor neutrinos and geoneutrinos.5)
Mentions: Upon entering the detector, ν̄e is captured by a free proton and an inverse β-decay reaction occurs, ν̄e +p → e++n. The positron deposits its energy and then annihilates, yielding two γ-rays (each 511 keV). The neutron is thermalized in (211.2 ± 2.6) μsec. and then captured by a proton in the following reaction, n + p → d + γ (2.22 MeV). Thus the inverse β-decay reaction provides a clear sequential signature of the prompt e+ and delayed γ with the definite time- and close space-correlations. The incident ν̄e energy is given by Eν ∼ Ee+ + 0.8 MeV, neglecting the small neutron recoil. Although the need to prevent any signals mimicking neutrino events is imperative, these signal correlations give a high rejection-power for background events. Nevertheless we can’t escape from the geoneutrino background. KamLAND has the first chance to search for geoneutrinos which are ν̄e’s originated from the U/Th decays inside the Earth. The radiogenic heat by the U/Th decays makes a dominant role in the energy generation of the Earth. We evaluated the detection rate of geoneutrinos in KamLAND, using various geophysical and geochemical models.5) In Fig. 3 a smooth broad histogram is the expected visible energy spectrum of positrons produced by reactor neutrinos, and 2 sharp peaks in the energy below 2.5 MeV are expected by geoneutrinos. In the reactor neutrino oscillation analysis, positrons with energies above 2.6 MeV are used to escape from the geoneutrino pollution.

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