Geoneutrinos: applications, future directions and defining the Earth’s engine Bill McDonough, *Yu Huang + Ondřej Šrámek and Roberta Rudnick Geology, U Maryland Steve Dye, Natural Science, Hawaii Pacific U and Physics, U Hawaii Shijie Zhong, Physics, U Colorado Fabio Mantovani, Physics, U Ferrara, Italy * graduate student + post-doc

Update on Earth Models: …views from the last year! Murakami et al (May , Nature): “…the lower mantle is enriched in silicon … consistent with the [CI] chondritic Earth model.” Campbell and O’Neill (March , Nature): “Evidence against a chondritic Earth” Zhang et al (March , Nature Geoscience): The Ti isotopic composition of the Earth and Moon overlaps that of enstatite chondrites. Fitoussi and Bourdon (March , Science): “Si isotopes support the conclusion that Earth was not built solely from enstatite chondrites.” Warren (Nov , EPSL): “Among known chondrite groups, EH yields a relatively close fit to the stable-isotopic composition of Earth.” - Compositional models differ widely, implying a factor of three difference in the U & Th content of the Earth

the future… Geoneutrino studies Nature & amount of Earth’s thermal power radiogenic heating vs secular cooling -abundance of heat producing elements (K, Th, U) in the Earth -clues to planet formation processes -amount of radiogenic power to drive mantle convection & plate tectonics -is the mantle layered or does it have large deep structures? estimates of BSE from 9TW to 36TW constrains chondritic Earth models estimates of mantle 1.3TW to 28TW superplume piles, e.g., source of Hawaii

Plate Tectonics, Convection,Geodynamo Radioactive decay driving the Earth’s engine!

after Jaupart et al 2008 Treatise of Geophysics Mantle cooling (18 TW) Crust R* (8 ± 1 TW) (Rudnick and Gao ‘03) Mantle R* (12 ± 4 TW) Core (~9 TW) - (4-15 TW) Earth’s surface heat flow 46 ± 3 (47 ± 2) (0.4 TW) Tidal dissipation Chemical differentiation *R radiogenic heat (after McDonough & Sun ’95) total R* 20 ± 4 11

Earth’s thermal evolution: role of K, Th & U Arevalo, McDonough, Luong (2009) EPSL Archean boundary Power (TW)

U in the Earth: ~13 ng/g U in the Earth Metallic sphere (core) <<1 ng/g U Silicate sphere 20* ng/g U *O’Neill & Palme (2008) 10 ng/g *Turcotte & Schubert (2002) 31 ng/g Continental Crust 1300 ng/g U Mantle ~12 ng/g U Th/U = 4, K/U ~10 4 (established by chondrites) Chromatographic separation Mantle melting & crust formation

Detecting Geoneutrinos from the Earth

Terrestrial Antineutrinos 238 U 232 Th 40 K ν e + p + → n + e MeV Energy Threshold 212 Bi 228 Ac 232 Th 1α, 1β 4α, 2β 208 Pb 1α, 1β νeνe νeνe 2.3 MeV 2.1 MeV 238 U 234 Pa 214 Bi 1α, 1β 5α, 2β 206 Pb 2α, 3β νeνe νeνe 2.3 MeV 3.3 MeV 40 K 40 Ca 1β1β Terrestrial antineutrinos from uranium and thorium are detectable Efforts to detect K geonus underway 31% 46% 20% 1%

Determining Th/U is a challenge

Summary of geoneutrino results MODELS Cosmochemical: uses meteorites – O’Neill & Palme (’08); Javoy et al (‘10); Warren (‘11) Geochemical: uses terrestrial rocks – McD & Sun ’95; Allegre et al ‘95; Palme O’Neil ‘03 Geophysical: parameterized convection – Schubert et al; Davies; Turcotte et al; Anderson Constrainting U & Th in the Earth McDonough, Learned, Dye (2012) Physics Today

Earth’s geoneutrino flux XU or Th  X (r 0 ) Flux of anti-neutrinos from X at detector position r 0 AXAX Frequency of radioactive decay of X per unit mass NXNX Number of anti-neutrinos produced per decay of X RR Earth radius a X (r)Concentration of X at position r  (r) Density of earth at position r Interrogating the composition of the continental crust and “thermo-mechanical pile” (super-plumes?) in the mantle …

Constructing a 3-D reference model Earth assigning chemical and physical states to Earth voxels

Estimating the geoneutrino flux at SNO+ - Geology - Geophysics seismic x-section

Global to Regional RRM SNO+ Sudbury Canada using only global inputs adding the regional geology improving our flux models

Predicted Global geoneutrino flux based on our new Reference Model Yu Huang et al (2013) arXiv: arXiv:

Models for understand Th & U in the Modern Mantle Inputs -Bulk Sil. Earth -Cont. Crust -Depleted Mantle Data vs Models BSE Models Geonu data

Structures in the mantle

Testing Earth Models Šrámek et al (2013) /j.epsl ; arXiv: /j.epsl arXiv:

Predicted Global geoneutrino flux - new Reference Model Predicted Mantle flux Šrámek et al (2013) /j.epsl ; arXiv: /j.epsl arXiv: Yu Huang et al (2013) arXiv: arXiv:

Present LS-detectors, data update? KamLAND, Japan (1kt) Borexino, Italy (0.6kt) from 2002 to Nov from May ‘07 to Dec ‘09 SNO+, Canada (1kt) under construction (online later this yr?)

Hanohano International ocean-based (50kt) LENA, EU (50kt) Daya Bay II China (20kt) Future detectors?

30m 100m DETECTOR DIMENSIONS inner detector - 50kt of organic liquid scintillator (Ø 26m) - 13,500 photomultipliers outer muon veto - water Čerenkov detector - 2m of active shielding LOCATION - mine or deep see plateau - depth of 4,000 m.w.e. to reduce  -&cosmogenic background proton decay solar neutrinos terrestrial neutrinos atmospheric neutrinos artificial neutrino sources supernova neutrinos diffuse SN neutrino background PHYSICS GOALS THE LENA DETECTOR AN OVERVIEW

Daya Bay II Geoneutrino Signal

Hanohano A Deep Ocean e Electron Anti-Neutrino Observatory Deployment Sketch Descent/ascent 39 min - multiple deployments - deep water cosmic shield - control-able L/E detection An experiment with joint interests in Physics, Geology, and Security

Earth’s radiogenic (Th & U) power 20 ± 9 TW* (23 ± 10) Prediction: models range from 11 to 28 TW Future: -SNO+ online 2013 …2020…?? -Daya Bay II -LENA -Hanohano? -Neutrino Tomography …

Geoneutrinos: ongoing efforts and wish list - Directionality - 40 K geonus - Detecting hidden objects down there

Measuring Antineutrino Direction Prompt e + Delayed n capture νeνe Neutrino direction Reconstructed event direction ΔθΔθ θnθn Neutron Kinetic Energy (keV) Neutron Emission Angle Terrestrial antineutrino direction measurement shows promise- Much to gain for geology Further study warranted Interaction kinematics Neutron absorption Position resolution Scintillator properties ΔθΔθ after Hiroko Watanabe’s past presentations

Potassium Geo-neutrinos? Absolute amount differs, but proportion of radiogenic heat production are similar 40 K ~19%, 232 Th 42% and 238 U 39% 40 K give the largest flux of geonus! Where is the potassium in the Earth? Continental crust has ~40%, mantle ~60% K may reside in the Earth’s core after Mark Chen’s past presentations

Using 106 Cd based detectors (M. Chen, 2006) Directional Dark Matter detectors (Dye et al, 2013) elastic scattering on electrons Detecting 40 K-geoneutrinos

Plenty of suggestions for Geo-reactors deep inside the Earth Based on: R. de Meijer & W. van Westrenen South African Journal of Science (2008)