Geoneutrinos: applications, future directions and defining the Earth’s engine

Bill McDonough, *Yu Huang +Ondřej Šrámek and Roberta RudnickGeology, 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 - 2012, Nature): “…the lower mantle is enriched in silicon … consistent with the [CI] chondritic Earth model.”

Campbell and O’Neill (March - 2012, Nature): “Evidence against a chondritic Earth”

Zhang et al (March - 2012, Nature Geoscience): The Ti isotopic composition of the Earth and Moon overlaps that of enstatite chondrites.

Fitoussi and Bourdon (March - 2012, Science): “Si isotopes support the conclusion that Earth was not built solely from enstatite chondrites.”

Warren (Nov - 2011, 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 dissipationChemical differentiation

*R radiogenic heat (after McDonough & Sun ’95)

total R*20 ± 4

1s

Earth’s thermal evolution: role of K, Th & U

Arevalo, McDonough, Luong (2009) EPSL

Arc

hean

bo

unda

ry

Pow

er (T

W)

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 ~104

(established by chondrites)

Chromatographic separationMantle melting & crust formation

2005

2010

2011

DetectingGeoneutrinosfrom the Earth

Terrestrial Antineutrinos

238U232Th40K

νe + p+ → n + e+

1.8 MeV Energy Threshold

212Bi

228Ac

232Th

1α, 1β

4α, 2β

208Pb

1α, 1β

νe

νe

2.3 MeV

2.1 MeV

238U

234Pa

214Bi

1α, 1β

5α, 2β

206Pb

2α, 3β

νe

νe2.3 MeV

3.3 MeV

40K 40Ca1β

Terrestrial antineutrinos from uranium and thorium are detectable

Efforts to detectK geonusunderway

31%

46% 20%

1%

Determining Th/U is a challenge

Summary of geoneutrino results

MODELSCosmochemical: 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 ‘03Geophysical: 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

X U or ThFX(r0) Flux of anti-neutrinos from X at detector position r0

AX Frequency of radioactive decay of X per unit mass

NX Number of anti-neutrinos produced per decay of X

R Earth radius

aX(r) Concentration of X at position r

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

seismicx-section

Global to Regional RRMSNO+SudburyCanada

using onlyglobal 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:1301.0365 

Models for understand Th & U in the Modern Mantle

Inputs- Bulk Sil. Earth- Cont. Crust- Depleted Mantle

Datavs

Models

BSE Models

Geonudata

Structures in the mantle

Testing Earth Models

Šrámek et al (2013) 10.1016/j.epsl.2012.11.001; arXiv:1207.0853

Predicted Global geoneutrino flux - new Reference Model

Predicted Mantle fluxŠrámek et al (2013) 10.1016/j.epsl.2012.11.001; arXiv:1207.0853

Yu Huang et al (2013) arXiv:1301.0365 

Present LS-detectors, data update? KamLAND, Japan (1kt)Borexino, Italy (0.6kt)

106+29-28

from 2002 to Nov 2009

9.9 +4.1-3.4

from May ‘07 to Dec ‘09

SNO+, Canada (1kt)

under construction (online later this yr?)

HanohanoInternational

ocean-based (50kt)

LENA,EU

(50kt)

Daya Bay IIChina(20kt)

Futuredetectors?

30m

100m

DETECTOR DIMENSIONSinner detector- 50kt of organic liquid scintillator (Ø 26m)- 13,500 photomultipliersouter muon veto- water Čerenkov detector- 2m of active shielding

LOCATION- mine or deep see plateau- depth of 4,000 m.w.e. to reduce m-&cosmogenic background

proton decaysolar neutrinos

terrestrial neutrinosatmospheric 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- 40K geonus- Detecting hidden objects down there

Measuring Antineutrino Direction

Prompt e+

Delayed n capture

νe Neutrino direction

Reconstructed event direction

Δθ

θ n

Neutron Kinetic Energy (keV)

Neutron Emission Angle

Terrestrial antineutrino directionmeasurement shows promise-• Much to gain for geology • Further study warranted

• Interaction kinematics• Neutron absorption• Position resolution• Scintillator properties

Δθ

after Hiroko Watanabe’s past presentations

Potassium Geo-neutrinos?

• Absolute amount differs, but proportion of radiogenic heat production are similar

• 40K ~19%, 232Th 42% and 238U 39%• 40K 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 106Cd based detectors (M. Chen, 2006)

Directional Dark Matter detectors (Dye et al, 2013)

elastic scattering on electrons

Detecting 40K-geoneutrinos

Plenty of suggestions forGeo-reactors deep inside the Earth

Based on: R. de Meijer & W. van WestrenenSouth African Journal of Science (2008)