Geo-neutrinos Status and Prospects

Steve DyeHawaii Pacific University

University of Hawaiip n

u du ud d

νe e+

W

Applied Antineutrino PhysicsOctober 2012

Outline

• Earth energy balance Aq = Mh – Mc(∂T/∂t)

• Radiogenic heat/geo-neutrinos• Detecting geo-neutrinos• Geo-neutrino data• Geo-neutrino analyses• Project updates• Prospects

νe e+

p nu du ud d

W

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Daya Bay II

TotalReactorGeo-nuThU

0

1

2

3

4

5

0 2 4 6 8 10

Surface Heat Flow

mW m-2

Total Flow Aq = 47 ±2 TW

Heat flow probe-thermal conductivity,dT/dx

Heat conduction-q = -k dT/dx

Pollack et al., 1993Added for Davies, Davies, 2010

Stat error only

Internal Heating

?

Geology predicts16-42 TW of

radioactive powerMass loss rate

dm/dt = -(6-15) tonne y-1

Internal heatingMh = 11 – 31 TW

~20% escapes to space as geo-neutrinos

~80% remains to heat planet

Other known sources ofinternal heating small

Thermal Evolution of Earth

Surface heat flow- Aq = 47 ±2 TW (Davies, Davies, 2010)

Internal heating- Mh = 11 to 31 TW (various models)

Planetary Urey ratio - U = Mh/Aq = 0.2 to 0.7

Temperature change rate:∂T/∂t = Aq/Mc (Mh/Aq – 1)

U = Mh/AqU > 1 T ↑ U < 1 T ↓

Geology predicts a cooling planet

Predicted Heating: Earth Models• Cosmochemical (CC)

– Enstatite chondrite - Javoy et al., 2010• ~11 TW heating

– Primitive mantle petrology- Palme & O’Neill, 2003• ~21 TW heating

• Geophysical (GP)– Viscosity with water- Crowley et al., 2011

• ~19 TW– Mantle convection- Turcotte, 1980

• ~38 TW heating

Heating in Earth: Mh = 11 - 38 TWwith 8 +/- 1 TW in crust

Earth Heating Elements

U, Th, K produce heat and geo-neutrinosexpected in silicate earth- crust and mantle

238U → 206Pb + 8α + 6e + 6 eν + 51.698 MeV     235U → 207Pb + 7α + 4e + 4 eν + 46.402 MeV     232Th→208Pb + 6α + 4e + 4 eν + 42.652 MeV     40K → 40Ca + e + eν + 1.311 MeV (89.3%)     40K + e → 40Ar + eν + 1.505 MeV (10.7%)               (1)

Goldschmidt Classification

  h(μW/kg)  l(kg‐1μs‐1) 

Uranium  98.5  76.4 Thorium  26.3  16.2 Potassium  3.33 x 10‐3 27.1 x 10‐3 

Lithophilic- “rock-loving”

3-October-2010 Steve Dye, HPU 8

PMTs measure position and amount of deposited energy

Antineutrino Detection

γγ

e+e-

γγ

n p+

γγ

Prompt event depositsenergy of Eν-0.8 MeV

Delayed event depositsenergy of 2.2 MeV

p+νe

Antineutrino (Eν>1.8 MeV)interacts with free proton

~10,000 γ/MeV

Antineutrino energy (MeV)

dn/d

E ν (1

0-44 c

m2 M

eV-1

)

238U

232Th

10-1

1

1.5 2 2.5 3 3.5

Geo-neutrino Event Spectrum

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

Th/U in source regions determines spectral shape

Neutrino energy (MeV)

arbi

trar

y un

its

δE = 7% E1/2

Th/U = 8

Th/U = 4

Th/U = 2

0

0.5

1

1.5

2

1.5 2 2.5 3 3.5

Neutrino Oscillations- θ13>0

221

232

231 mmm δδδ >>≈

( ) ( )[ ]132

212

122

134 2sin5.0)(sin)2(sincos1 θθθ +Δ−≅eeP

)]}(sin)2(sin)(sin)2()[cos2(sin

)(sin)2(sin)({cos1

322

122

312

122

132

212

122

1343

Δ+Δ+

Δ−=

θθθ

θθνeeP

eELmjiji νδ /)(27.1 2=Δ 222

ijji mmm −≡δ

3-ν mixing

( )[ ] 024.013.13

212

213

4 536.0)2(sin)2(sincos5.01 +−=+−≅ θθθeeP

Fogli et al., 2011 ; An et al., 2012 ; Ahn et al., 2012

Error dominatedby solar mixing

angle

Energy (MeV)

P ee/<

P ee>

Oceanic planet

Continental planet

0.99

1

1.01

1.02

1.03

1.04

1.05

2 2.5 3

Dye, 2012Rev. Geophys. 50, RG3007

Adjust Average Oscillation Probabilityθ13 : 0 º → 10 º

<Pee> : 0.58 → 0.54

Lowers reactor & crust flux predictions

Using <Pee> overestimates

mantle signal and

underestimates Th/U

Pronounced at sitesenriched in U & Th such as

Sudbury basin

Perry et al., 2009

Reactor Antineutrino Background

Geo Geo ννσ(E)

Φ(E) N(E)

(Enomoto, Neutrino Sciences 2007)

)/27.1(sin)2(sin1 221

212

2

eeeELmP ννν θ Δ−≅→

Expected reactor signal3-60 TNU depending on location

OLD- Kamioka

OLD- θ13=0

Existing Gν Detectors

1 kT LS80% dodecane

20% PCw/ 1.36 g/l PPO

~1800 PMTs34% solid angle

~250 pe/MeVvis

(5.98±0.12)x1031 p

KamLAND- Kamioka, Japan

Both existing detectorsare in Eurasia at

~40 ⁰ N and separatedin longitude by ~120 ⁰

0.278 kT PCw/ 1.5 g/l PPO

2212 8-in PMTs~30% solid angle

~500 pe/MeVvis

~0.17x1031 p

Borexino- Gran Sasso, Italy

Published Gν Data

Total events- 841Background- 730±32

Geo-nu- 111±43

Gando et al., 2011 Nature Geoscience 4, 647

KamLAND

Mar-02 to Nov-09 : 3.49±0.07 TNU-1

Total events- 15Background- 5.3±0.3

Geo-nu- 9.7±3.9

Borexino

Dec-07 to Dec-09 : 0.152 TNU-1

Bellini et al., 2010Phys. Lett. B 687, 299

Gν Data Analysis

Gando et al., 2011 Nature Geoscience 4, 647

unconstrained fitNU = 65 ; NTh = 33

Th/U ~ 8

ε(U) = 0.807 ε(Th) = 0.751

“Fixing” Th/U=3.9N(U+Th) = 106±29

KamLAND

40.0±10.5(stat)±11.5 (sys) TNU

systematic > statistical

Best fit: 9.9(+4.1/‐3.4) gν events

ε=0.85±0.01

Bellini et al., 2010Phys. Lett. B 687, 299

Borexino

64±25(stat)±2(sys) TNUstatistical >> systematic

“Fixing” Th/U=3.9

Surface heat flux

Observed Gν Residual mantle GνGν Analysis- I

Gando et al., 2011 Nature Geoscience 4, 647

Old value. Revised lowerby Coltorti et al., 2011. Mh (U+Th) = 20 ± 9 TW GC

modelGC

model

BX > KLbut consistent

with BX=KL

Gν Analysis- II

1.7 ≤ Th/U ≤ 3.9

• Geophysical- consistent• Cosmochemical- excluded ~90% CL

No model excluded at ~>2σ

Fiorentini et al., 2012arXiv:1204.1923v1

Rmantle = 23 ± 10 TNUR>0 at ~2.4σ

Mh(U+Th) > 19 TW (68% CL)

Residual mantle signalw/ model comparisons

Gν Analysis- III

Homogeneousmantle

DM w/ enrichedbasement layer

KamLAND (2011) data consistent with models,

prefers Mh < Aq

Borexino (2010) dataconsistent with GP and

Mh = Aq

Dye, 2012Rev. Geophys. 50, RG3007

KL+BX (weighted averages)consistent w/ GP & GC

weakly exclude CC

Min Mh = 28 ± 13 TWMax Mh = 33 ± 16 TW

νν

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Gran Sasso

TotalReactorGeo-nuThU

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Kamioka- now

TotalReactorGeo-nuThU

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

KamiokaTotal

Reactor

Geo-nu

Th

U

0

0.5

1

1.5

2

2.5

0 2 4 6 8 10

Predicted Signals: Existing Sites

Kamioka before and after all

reactors shutdown

A new Gνbeginning for KL

BX can operate for many years beforesystematic uncertainty significant

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Pyhäsalmi

TotalReactorGeo-nuThU

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Baksan

TotalReactorGeo-nuThU

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Sudbury

TotalReactorGeo-nuThU

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Homestake

TotalReactorGeo-nuThU

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Predicted Signals: Continental Sites

Continental Observatories

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Daya Bay II

TotalReactorGeo-nuThU

0

1

2

3

4

5

0 2 4 6 8 10

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Pacific

TotalReactorGeo-nuThU

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Resolving Radiogenic Heating

Assumes H = 20 TW Systematic error only

Continental δ(Mh)/Mh ~ 0.4

Existing δ(Mh)/Mh ~ 0.3

Oceanic δ(Mh)/Mh ~ 0.15

Dye, 2012Rev. Geophys. 50, RG3007

Enriched Deep Mantle?Pyhäsalmi

HomestakeBaksan

Sramek et al., 2012arXiv:1207.0853

Neutrino energy (MeV)

Eve

nts/

10 k

eV (1

032p

y)-1

Pacific

TotalReactorGeo-nuThU

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Deep ocean observatoryresolves earth heating,

potentially super-plumes

Pacific

SudburyGran Sasso

Kamioka

Project Updates

• Borexino– “… doubled statistics and improved FV definition... Data look

nice.” Aldo Ianni

• KamLAND– “… acquiring good data but wont publish for a year until reactors

come back…” Kunio Inoue

• SNO+: Data next year, crust study in progress

• LENA: White paper published in Astropart. Phys.- M. Wurm

• Baksan: Discussing10-50 kT detector- V. Sinev

• Daya Bay II:10-50 kT detector- fun challenge to extract Gν signal

• Hanohano: possible synergy with Watchman, geology

Gν Summary

• Observing planetary U & Th; no Th/U; no K; no direction• KL & BX data: Mantle radiogenic heating >10 TW (1σ)

– Beginning to constrain earth heating

• Potential for resolution of geological models– Constrain thermal evolution, formation processes, origin

• Network of continental observatories– KL, BX, SNO+, LENA, Baksan, Homestake– 50 TNU-1 δm ≈ 3 TNU

• Single oceanic observatory– Hanohano 3 TNU-1 δm ≈ 3 TNU– Potential to resolve super-plumes

• Study as background to precision θ12 and reactor monitor

Thank You

• Backup slides follow

Planetary Power

Surface heat flow- Aq

Internal heating- Mh

Heat to change temperature- Mc(∂T/∂t)

Aq = Mh – Mc(∂T/∂t)

Temperature change rate: ∂T/∂t = Aq/Mc (Mh/Aq – 1)

Planetary Urey ratio - U = Mh/Aq

Cross Sections−− +→+ ee ee νν

e

e

EmE

Te ν

ν

21max +=

442

2max3max2

max2 10

2)1()1(1

3)1(43.0)( −×

⎥⎥⎦

⎤

⎢⎢⎣

⎡+−

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

−−++=ee

e

e ETmxx

ETE

xTxE ee

νν

ννσ

nepe +→+ +ν

( ) 44222 101)(52.9)( −×Δ−−Δ−=eee

EmEE ep νννσ

ee mETe

−Δ−= ν

Antineutrino Interactions

Electron elastic scattering• νe + e- → νe + e-

• Electron target– No energy threshold

• Cross-section– σ(Eν)~4.0x10-45 Eν

1 cm2

Inverse β-decay• νe + p → n + e+

• Proton target– Ethresh ≈ 1.80 MeV

• Cross-section– σ(Eν)~9.5x10-44 (Eν-1.3)2 cm2

p nu du ud d

νee+

W

e- e-

νeνe

Z0

Nue-bar elastic scattering observed by Reines, Gurr, Sobel in 1976

Sensitivity below 1.8 MeV; no tag

4 e- / p+ in CH2 LS

Resolve e- direction to find signal?

Cross Sections

Nue-bar quasi-elastic scatteringused by Reines and Cowan in 1950’s

Coincidence counting; weak direction

Works great for geo-nue-bars

Uncertainties small

Geo-neutrino Intensity Spectra

[ ] [ ] βν QeZAZA e ++++→ 1,,

)(e

EmQw ee νβ −+=

[ ] 2/122)( eee mEmQpe

−−+= νβ

( )2122/)( ηγπηγννν iepEwdEEdn ee eee

+Γ∝ −

22 )1(1 +−= Zαγ

ee pwZ )1( +=αη

Internal heating and geo-neutrinos connected

per decay

Detected Spectra

x =

Inverse-β Interaction Kinematicstr

ansv

erse

longitudinal

Initial-ptrans= 0

Final-ptrans= 0

ppννe

n

e+

θn

e+

θe

pν

θ'e

WatanabeBatygov

Coincidence Counting

Prompt event• Positron

– Ee ≈ Eν – 1.8 MeV– Evis ≈ Eν – 0.8 MeV– Ionization energy + 2γ– Deposition time ~ few ns– <Re> ~ 0.4 cm

Delayed event• Neutron

– En ≈ 1-100 keV– Thermal diffusion– Evis depends capture nucleus– Deposition time ~ 20 – 200 μs– <Rn> ~ 5 – 15 cm

Watanabe

Seeing with Sound

Seismology- PREM• density profile• internal structure• solid vs liquid phase

(Dziewonski, Anderson, 1981)

Chemical Affinity

U, Th, K in silicate earth- crust and mantle only

Goldschmidt Classification

Lithophilic- “rock-loving”

Crust Model

Seismic model- CRUST 2.0 (Bassin et al., 2000)Composition model- (Rudnick,Gao, 2003)

Heating in crust (Mh)crust = 8 ±1 TW

Non-antineutrino Background

Mei and Hime, 2006

Fast neutronbackgroundfrom muonsoutside veto<1 TNU at

Gran Sasso

Abe et al., 2010

Isotope background (β,n) ~0.5 TNU

Accidental background3.4±0.2 TNU KL (2005)1.3±0.2 TNU BX (2010)

Radon contamination210Po → 206Pb + α

13C(α,n)16O<0.3 TNU

Gν Analysis- II

Fiorentini et al., 2012arXiv:1204.1923v1

θ13>0 decreases expected crust

KL (Enomoto et al., 2007) .54/.59=.92BX (Coltorti et al., 2011) .54/.57=.95

Increased total signalsKL R(U+Th) 40→43 TNUBX R(U+Th) 64→67 TNU

R(U+Th) >0at ~4.2σ

Add to increase mantle signalMantle = Total – Crust

Gando et al., 2011

Gν Analysis- III

Dye, 2012arXiv:1111.6099v2

Weighted average

MethodM = N - B – C

δM = (N + δB2 + δC2)1/2

AssumptionsTh/U = 3.9 ; C model

MKL= MBX

Combined result:consistent w/ GP, GCweakly excludes CC

Rmantle = 17 ± 10 TNU

Sramek et al., 2012

BX > KLbut consistent

with BX=KL

GP

GC

CC

Man

tle ra

te (T

NU

)

0

10

20

30

40

50

60

70

80

KL(2011) BX(2010) KL+BX

Projection to Year 2020

KamLAND : 9 TNU-1 δm = ± 6 TNU

Borexino : 1 TNU-1 δm = ± 10 TNU

SNO+ : 3 TNU-1 δm = ± 9 TNU------------------------------------------------Total : 13 TNU-1 δm = ± 4-5 TNU

OR

GeoHano : 3 TNU-1 δm = ± 3 TNUGeoHano : 6 TNU-1 δm = ± 2 TNU

OR

Network- Five x 10 TNU-1 δm = ± 3 TNU