Geoneutrino Overview Sanshiro Enomoto KamLAND Collaboration RCNS, Tohoku University Review of Geoneutrino Physics (with KamLAND) KamLAND Result and Prospects Physics with Proposed Detectors ce 2007 – Deep Ocean Anti-Neutrino Observatory Workshop, Univ. of Hawaii at Manoa, March 23-25 2007
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Geoneutrino Overview
Sanshiro EnomotoKamLAND CollaborationRCNS, Tohoku University
1 . Review of Geoneutrino Physics (with KamLAND)2 . KamLAND Result and Prospects3 . Physics with Proposed Detectors
Neutrino Science 2007 – Deep Ocean Anti-Neutrino Observatory Workshop, Univ. of Hawaii at Manoa, March 23-25 2007
Geoneutrinos
• Geoneutrinos are produced by
– Direct measurement of HPE– U:~8TW, Th: ~8TW, K: ~3TW
• Geoneutrinos are detected by
– Two consecutive signals– Threshold 1.8 MeV
– Not sensitive to 40K;other targets discussed [M.C.Chen (2005)]
e4040
e4208232
e-4206238
νeCaK
ν4e4He6PbTh
ν6e 6 He8PbU
nepe
Threshold: 1.8 MeV
KamLAND: The First Detector Sensitive to Geoneutrinos
• Yields light on ionization (8000 photons / MeV)• Mainly consists of only C and H
20m
Liquid Scintillator
O
N
1.5g/l
HHHHHHHHHHHHHCCCCCCCCCCCCH HHHHHHHHHHHH
80%
CH3CH3
CH320%
Liquid Scintillator 1000 tonContained in plastic balloon
17-inch PMT 132520-inch 554
Detector Center
Surrounded by
(PMT : Photo Multiplier Tube, a photo sensor)
KamLAND Location
JapanTrench
Sea of Japan
You are here
Geological Setting• Boundary of Continent and Ocean• Island Arc (Orogenic)• ‘Hida’ Metamorphic Zone• Zn, Pb, limestone mine (skarn)• Surrounded by Gneiss Rocks
KamLAND
KamLAND
KamLAND is surrounded bya number of nuclear reactors
• BSE composition by [McDonough1999]• Crustal composition by [Rudnick et al. 1995]• Crustal thickness by CRUST 2.0• Uniform Mantle Model• No U/Th in the Core
With 1032 target protons,•U-Series 32 events / year•Th-Series 8 events / year
Geoneutrino Origination PointsDetectable at KamLAND (MC)
South AmericaAntarctic
Australia
KamLAND
Greenland
50% within 500km25% from Mantle
Total 19 is predictedfor KamLAND 749 days
Uncertainties of the Model
• Geochemical / Geophysical datararely come with error estimation
• Fiorentini et al. (2005)– Error is given as “spread in published estimates”
• Fogli et al. (2006): GeoNeutrino Source Model (GNSM)– Correlations (reservoirs, elements) added
• Enomoto et al. (2005)– Inversion framework discussed
Local Geological Effects
• ~50% of flux comes within ~500km radius• ~25% within ~50km
• Characteristic U/Th depletion in Japan Arc [Togashi et al. (2000)]
– U: -17%, Th: 22% ⇒ affects total flux at 6.4% (U) and 8.4% (Th)
• Surface heterogeneity [Enomoto et al. (2005)]
– 20% flux variation possible ⇒ 3.2% uncertainty in total flux
• We have to discriminate the global and regional signature• Correlation matrix used by GNSM (Fogli et al (2006)) could be extended ?? if correlation coefficients among different crustal types are given.
Plumes, Ocean Ridges, …
Neutrino Detector on Plume
Neutrino Detector on Mid-Ocean Ridge
At Tahiti, 13% comes from “hot” mantle⇒ sensitive to a factor enrichment
If the mantle beneath mid-ocean ridgeIs depleted by a factor, it should be visible
Portable detector (like Hanohano)will open new application
Summary
• Geoneutrino provides a direct measurement of heat producing elements (HPE)
• KamLAND measurement will be improved– Reduced systematic error for existing data– Radioactive BG reduction by LS distillation
• Multiple site measurement is important– Reduction of local geological effects– Separation of mantle and core– Sensitivity to regional characteristics– No nuclear reactor BG
• Wish List– Error estimations for U/Th content in each reservoir– Better resolution crustal map