1. Geoneutrino Overview 1．Review of Geoneutrino Physics (with KamLAND)
2．KamLAND Result and Prospects
3．Physics with Proposed Detectors
Sanshiro Enomoto
KamLAND Collaboration
RCNS, Tohoku University
Neutrino Science 2007 – Deep Ocean Anti-Neutrino Observatory Workshop, Univ. of Hawaii at Manoa, March

2. Geoneutrinos Geoneutrinos are produced by Geoneutrinos are detected 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)]
Threshold: 1.8 MeV

3. KamLAND: The First Detector Sensitive to Geoneutrinos
Detector Center
Liquid Scintillator 1000 ton Contained in plastic balloon
Surrounded by
17-inch PMT 1325
20-inch
(PMT : Photo Multiplier Tube, a photo sensor)
Liquid Scintillator
20m
Yields light on ionization (8000 photons / MeV)
Mainly consists of only C and H

4. KamLAND Location Geological Setting KamLAND You are here Sea of Japan
Boundary of Continent and Ocean
Island Arc (Orogenic)
‘Hida’ Metamorphic Zone
Zn, Pb, limestone mine (skarn)
Surrounded by Gneiss Rocks
KamLAND
You are here
Sea of Japan
KamLAND
Japan Trench
KamLAND is surrounded by a number of nuclear reactors

5. First Result from KamLAND
[T. Araki et al. (2005)]
Fiducial Volume: ton
Live-time: days
Efficiency: %
Expected Geoneutrinos
U-Series： 14.9
Th-Series：4.0 Backgrounds
Reactor： ±7.2
(α,n) ： ±11.1
Accidental：2.38±0.01 BG total： ±13.3
Observed： 152
Number of Geoneutrinos: 25
＋19
－18

6. A Reference Earth Model to Predict Flux
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
Expected Geoneutrino Flux
U-Series
2.3x106 [1/cm2/sec]
Th-Series
2.0x106 [1/cm2/sec]
Geoneutrino Origination Points Detectable at KamLAND (MC)
50% within 500km 25% from Mantle
KamLAND
With 1032 target protons,
U-Series
32 events / year
Th-Series
８ events / year
Australia
Greenland
Total 19 is predicted for KamLAND 749 days
Antarctic
South America

7. Uncertainties of the Model
Geochemical / Geophysical data rarely 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

8. 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
Vertical heterogeneity ???
~500km

9. Other Source of Uncertainties
Crustal Thickness Map Resolution (2×2 deg)
3~4% Total Flux Uncertainty
Neutrino Oscillation Parameter (sin22θ=0.82±0.07)
6% Flux Uncertainty
Comparison of CRUST 2.0 and Zhao et al.
CRUST2.0
Propagation of crustal thickness error
Zhao et al. (1992)

10. Summary of Total Flux Uncertainties
Global Modeling (not uncertainty; our interest)
BSE comopsition: ~20%
Mantle models (uniform / layered): <3%
Local Geological Effects
Island Arc Characteristics: 6-8%
Surface Geology Heterogeneity: 3.2%
Vertical Heterogeneity: ???
Other Uncertainties
Crustal Thickness Map Resolution: 3~4%
Neutrino Oscillation Parameter: 6%

11. Flux Prediction from Earth Models
Scale Bulk Composition
Geoneutrino Flux [1/cm2/sec]
Fix Crustal Composition,
Parameterize Mantle
U+Th Mass [kg]

12. KamLAND Result Number of Geoneutrinos: 25 Fiducial Volume: 408 ton
[T. Araki et al. (2005)]
Fiducial Volume: ton
Live-time: days
Efficiency: %
Expected Geoneutrinos
U-Series： 14.9
Th-Series：4.0 Backgrounds
Reactor： ±7.2
(α,n) ： ±11.1
Accidental：2.38±0.01 BG total： ±13.3
Observed： 152
Number of Geoneutrinos: 25
＋19
－18

13. KamLAND Spectrum Analysis
Parameters NU, NTh: Number of Geoneutrinos sin22θ, Δm2 : Neutrino Oscillation α1, α2: Backgrounds Uncertainties
Total Number of U and Th
KamLAND is insensitive to U/Th ratio → adopt U/Th ~ 3.9 from Earth science
Number of Geoneutrinos：28.0
99% C.L. upper limit：70.7 events
Significance 95.3% (1.99-sigmas)
＋15.6
－14.6
Discrimination of U and Th

14. Comparison with Earth Model Predictions
KamLAND 99% Limit
Geoneutrino Flux [1/cm2/sec]
KamLAND 1-σ Range
Earth Model Prediction
U+Th Mass [kg]
Consistent with BSE model predictions
99%C.L. upper limit too large to be converted to heat production (No Earth models applicable)

15. KamLAND Problem (α,n) BG Reactor Neutrino BG 222Rn 210Pb n + p → n + p
22.3 y
n + p → n + p
13C (α,n) 16O
210Bi
210Po
206Pb
Cross-section error: 20%
5.013 d
138.4 d
stable
Quenting factor error: 10%
210Po decay rate error 14%

16. (α,n) Background error had been reduced
KamLAND Prospects (1)
(α,n) Background error had been reduced
New (α,n) Cross section data available
Vertex reconstruction algorithm improved
Proton quenching factor measurement
210Po-C source calibration performed ⇒ (α,n) error reduced from ~26% to ~5%
P quenching measurement
Po-C Calibration (MC/Data)

17. KamLAND Prospects (2)
LS Distillation in Progress ⇒ removes radioactivity by 10-5
we remove these
BEFORE
AFTER
Another 749 days operation after purification,
Error is reduced：from 54% to 28% (error is dominated by reactor neutrinos)
Significance： 99.96%

18. KamLAND Prospects
Upper limit (~40TW) comparable with heat flow (~40TW)
28% uncertainty

19. Future Geoneutrino Experiments
Project
Location
Mass (kton)
Depth (m.w.e.)
KamLAND
Kamioka / Japan
1.0
2700
Borexino
Gran Sasso / Italy
0.3
3700
SNO+
Sudbury / Canada
0.7
5400
Hano-hano
Hawaii / U.S. 10
4000
BNO
Baksan / Russia
4800
LENA
Phyasalm / Finland Nestor / Greece 50
HSD
Kimballton / U.S. Homestake / U.S. Soudan / U.S.
100

20. The World Map of Geoneutrino Flux
Typical Rate
from Crust
30~70 /1032P/year
from Mantle
~10 /1032P/year

21. Reactor Neutrino Backgrounds
KamLAND-II 750 days
（expected）
without reactor BG

22. The World Map of Geoneutrino S/N Ratio

23. Geoneutrino Flux @ Future Detector Sites
KamLAND
SNO+
Hanohano
Borexino
LENA

24. Required Exposure for 20% precision determination
Typical Time
on CC, estimate BSE
0.5~1 [1032P・year]
on CC, estimate M
~30 [1032P・year]
on OC, estimate M
4.5 [1032P・year]
Sensitive to
Crustal Composition
Sensitive to
Mantle Composition
Worst Place

25. Sensitivity to “Regional” Structure
Kamioka / Island Arc
Gran Sasso / Mesozoic Crust
Hawaii / Oceanic Island
Sudbury / Archean Crust
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.

26. Plumes, Ocean Ridges, … Neutrino Detector on Plume
At Tahiti, 13% comes from “hot” mantle ⇒ sensitive to a factor enrichment
Neutrino Detector on
Mid-Ocean Ridge
If the mantle beneath mid-ocean ridge
Is depleted by a factor, it should be visible
Portable detector (like Hanohano) will open new application

27. 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

28. Appendix
Backup Slides

29. Geoneutrino Spectrum

30. Geoneutrino Angular Distribution at Kamioka