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 23-25 2007

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

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 554 (PMT : Photo Multiplier Tube, a photo sensor) Liquid Scintillator 20m Yields light on ionization (8000 photons / MeV) Mainly consists of only C and H

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

First Result from KamLAND [T. Araki et al. (2005)] Fiducial Volume: 408 ton Live-time: 749 days Efficiency: 68.7% Expected Geoneutrinos U-Series： 14.9 Th-Series：4.0 Backgrounds Reactor： 82.3±7.2 (α,n) ： 42.4±11.1 Accidental：2.38±0.01 BG total： 127.4±13.3 Observed： 152 Number of Geoneutrinos: 25 ＋19 －18

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

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

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

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)

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%

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

KamLAND Result Number of Geoneutrinos: 25 Fiducial Volume: 408 ton [T. Araki et al. (2005)] Fiducial Volume: 408 ton Live-time: 749 days Efficiency: 68.7% Expected Geoneutrinos U-Series： 14.9 Th-Series：4.0 Backgrounds Reactor： 82.3±7.2 (α,n) ： 42.4±11.1 Accidental：2.38±0.01 BG total： 127.4±13.3 Observed： 152 Number of Geoneutrinos: 25 ＋19 －18

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

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)

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%

(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)

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%

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

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 4000 4000 HSD Kimballton / U.S. Homestake / U.S. Soudan / U.S. 100 1850 4200 2070

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

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

The World Map of Geoneutrino S/N Ratio

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

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

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.

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

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

Appendix Backup Slides

Geoneutrino Spectrum

Geoneutrino Angular Distribution at Kamioka