Geo-neutrinos
Status and Prospects
SNOLAB Grand Opening Workshop
May 2012
e+
νe
W
u
pu
Steve Dye
Hawaii Pacific University
d
d
u
d
n
Outline
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Radiogenic heat/thermal evolution
Radiogenic heat/geo-neutrinos
Detecting geo-neutrinos
Geo-neutrino data
Geo-neutrino analyses
Project updates
Prospects
Planetary Power
Aq = Mh – Mc(∂T/∂t)
Surface heat flow- Aq
Internal heating- Mh
Heat to change temperature- Mc(∂T/∂t)
Temperature change rate:
∂T/∂t = Aq/Mc (Mh/Aq – 1)
Planetary Urey ratio - U = Mh/Aq
Surface Heat Flow
Pollack et al., 1993
Added for Davies, Davies, 2010
mW m-2
Heat flow probethermal conductivity,
dT/dx
Heat conductionq = -k dT/dx
Total Flow Aq = 47 ±2 TW
Internal Heating
Geology predicts
16-42 TW of
radioactive power
Mass loss rate
dm/dt = -(6-15) tonne y-1
?
~20% escapes to space
as geo-neutrinos
~80% remains to heat planet
Other known sources of
internal heating small
Internal heating
Mh = 13 – 34 TW
Thermal Evolution of Earth
Temperature change rate:
∂T/∂t = Aq/Mc (Mh/Aq – 1)
U = Mh/Aq
U>1 T↑
U<1 T↓
Surface heat flow- Aq = 47 ±2 TW (Davies, Davies, 2010)
Internal heating- Mh = 13 to 34 TW (various models)
Planetary Urey ratio - U = Mh/Aq = 0.28 to 0.70
Geology predicts a cooling planet
Earth Heating Elements
U → 206Pb + 8α + 6e + 6 e + 51.698 MeV
235
U → 207Pb + 7α + 4e + 4 e + 46.402 MeV
232
Th→208Pb + 6α + 4e + 4 e + 42.652 MeV
40
K → 40Ca + e + e + 1.311 MeV (89.3%)
40
K + e → 40Ar + e + 1.505 MeV (10.7%)
238
Uranium
Thorium
Potassium
h(μW/kg)
98.5
26.3
-3
3.33 x 10
-1
(1)
-1
l(kg μs )
76.4
16.2
-3
27.1 x 10
U, Th, K produce heat and geo-neutrinos
Geo-neutrino Intensity Spectra
A, Z   A, Z  1  e   e  Q
per decay
we  (Q  me  E e )

pe  (Q  me  E e )
2

2 1/ 2
 me
dn( E e ) / dE e  we E e 2 pe2 1e   i 
2
  1   2 ( Z  1) 2
   (Z  1) we pe
Internal heating and geo-neutrinos connected
Antineutrino Interactions
Inverse β-decay
Electron elastic scattering
• νe + e- → νe + e• Electron target
• νe + p → n + e+
• Proton target
– No energy threshold
• Cross-section
• Cross-section
– σ(Eν)~4.0x10-45 Eν1 cm2
e-
– Ethresh ≈ 1.80 MeV
– σ(Eν)~9.5x10-44 (Eν-1.3)2 cm2
e+
νe
e-
W
Z0
p
νe
νe
u
d
u
u
d
d
n
Cross Sections
 e  e   e  e
Tmax 
E e
1  me 2 E e
2
 2


E
T
m
T



 e ( E e )  0.43 x Tmax  ( x  1) 2 e 1  (1  max )3   x( x  1) e max
2
3 
E
2
E




e
e



 1044

 e  p  e  n
 p ( E e )  9.52( E e  )2 1  me2 E e  2  10 44
Te  E e    me
Cross Sections
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?
Nue-bar quasi-elastic scattering
used by Reines and Cowan in 1950’s
Coincidence counting; weak direction
Works great for geo-nue-bars
Uncertainties small
Detected Spectra
Inverse-β Interaction Kinematics
transverse
n
Initialptrans= 0
νe
pν
Finalptrans= 0
p
θ'
longitudinal
e+
Batygov
Watanabe
θn
pν
θe
e
e+
Coincidence Counting
Prompt event
• Positron
–
–
–
–
–
Delayed event
• Neutron
Ee ≈ Eν – 1.8 MeV
Evis ≈ Eν – 0.8 MeV
Ionization energy + 2γ
Deposition time ~ few ns
<Re> ~ 0.4 cm
–
–
–
–
–
Watanabe
En ≈ 1-100 keV
Thermal diffusion
Evis depends capture nucleus
Deposition time ~ 20 – 200 μs
<Rn> ~ 5 – 15 cm
Antineutrino Detection
Antineutrino (Eν>1.8 MeV)
interacts with free proton
γ
νe
e-
p+
n
p+
γ
e+
γ
Prompt event deposits
energy of Eν-0.8 MeV
Delayed event deposits
energy of 2.2 MeV
~10,000 γ/MeV
PMTs measure position and amount of deposited energy
3-October-2010
Steve Dye, HPU
15
238
Geo-neutrino Event Spectrum
U
232
1α, 1β
Pa
234
1α, 1β
νe
2.3 MeV
νe
2.1 MeV
5α, 2β
214
Bi
Pb
Ac
228
4α, 2β
νe
3.3 MeV
νe
2.3 MeV
2α, 3β
206
Th
212
Bi
1α, 1β
Th/U in source regions determines spectral shape
208
Pb
Neutrino Oscillations- θ13>0
3-ν mixing
Pee3  1  {cos 4 (13 ) sin 2 (212 ) sin 2 ( 21)
 sin 2 (213 )[cos2 (212 ) sin 2 ( 31)  sin 2 (212 ) sin 2 ( 32 )]}
 ji  1.27( m2ji L) / E e

2
2
2
m31
 m32
 m21
m2ji  m2j  mi2
Error dominated
by solar mixing
angle

Pee  1  cos 4 13 sin 2 (212 ) sin 2 ( 21)  0.5 sin 2 213 


024
Pee  1  0.5 cos4 13 sin 2 (212 )  sin 2 (213)  0.536 ..013
Fogli et al., 2011 ; An et al., 2012 ; Ahn et al., 2012
Average Oscillation Probability
θ13 : 0 º → 10 º
<Pee> : 0.58 → 0.54
Lowers reactor & crust flux predictions
Using <Pee> overestimates
a(U) & a(Th) and
underestimates Th/U
Pronounced at sites
enriched in U & Th such as
Sudbury basin
Perry et al., 2009
Dye, 2012
arXiv:1111.6099v2
Reactor Antineutrino Background
Φ(E)
OLD- θ13=0
2
P e  e  1  sin 2 (212 ) sin 2 (1.27m21
L / E e )
N(E)
σ(E)
Geo ν
(Enomoto, Neutrino Sciences 2007)
OLD- Japan?
Expected reactor signals
depend on location
Non-neutrino Background
Fast neutron
background
from muons
outside veto
<1 TNU at
Gran Sasso
Accidental background
3.4±0.2 TNU KL (2005)
1.3±0.2 TNU BX (2010)
Mei and Hime, 2006
Isotope background (β,n) ~0.5 TNU
Radon contamination
210Po → 206Pb + α
13C(α,n)16O
<0.3 TNU
Abe et al., 2010
Existing Gν Detectors
KamLAND- Kamioka, Japan
1 kT LS
80% dodecane
20% PC
w/ 1.36 g/l PPO
~1800 PMTs
34% solid angle
Borexino- Gran Sasso, Italy
0.278 kT PC
w/ 1.5 g/l PPO
2212 8-in PMTs
~30% solid angle
~500 pe/MeVvis
~0.17x1031 p
~250 pe/MeVvis
(5.98±0.12)x1031 p
Both existing detectors
are in Eurasia at
~40 ⁰ N and separated
in longitude by ~120 ⁰
Gν Data: Existing Detectors
KamLAND
Borexino
Mar-02 to Nov-09 : 3.49±0.07 TNU-1
Dec-07 to Dec-09 : 0.152 TNU-1
Total events- 841
Background- 730±32
Geo-nu- 111±43
Gando et al., 2011
Nature Geoscience 4, 647
Total events- 15
Background- 5.3±0.3
Geo-nu- 9.7±3.9
Bellini et al., 2010
Phys. Lett. B 687, 299
Gν Data Analysis
Borexino
KamLAND
unconstrained fit
NU = 65 ; NTh = 33
Th/U ~ 8
Best fit:
9.9(+4.1/-3.4) gν events
ε=0.85±0.01
ε(U) = 0.807
ε(Th) = 0.751
“Fixing” Th/U=3.9
N(U+Th) = 106±29
“Fixing” Th/U=3.9
40.0±10.5(stat)±11.5 (sys)
TNU
systematic > statistical
Gando et al., 2011
Nature Geoscience 4, 647
64±25(stat)±2(sys) TNU
statistical >> systematic
Bellini et al., 2010
Phys. Lett. B 687, 299
Gν Analysis- I
Observed Gν
Observed Gν – Predicted Crust
Surface heat flux
Old value. Revised lower
by Coltorti et al., 2011.
Mh (U+Th) = 20 ± 9 TW
Gando et al., 2011
Nature Geoscience 4, 647
Gν Analysis- II
Increased total signals
KL R(U+Th) 40→43 TNU
BX R(U+Th) 64→67 TNU
R(U+Th) >0
at ~4.2σ
θ13>0 decreases expected crust
KL (Enomoto et al., 2007) .54/.59=.92
BX (Coltorti et al., 2011) .54/.57=.95
Gando et al., 2011
Add to increase mantle signal
Mantle = Total – Crust
Fiorentini et al., 2012
arXiv:1204.1923v1
Gν Analysis- II
Residual mantle signal
w/ model comparisons
1.7 ≤ Th/U ≤ 3.9
Rmantle = 23 ± 10 TNU
R>0 at ~2.4σ
• Geophysical- consistent
• Geochemical- excluded >90% CL
• Cosmochemical- constrained
Mh(U+Th) > 19 TW (68% CL)
No model excluded at ~>2σ
Fiorentini et al., 2012
arXiv:1204.1923v1
Gν Analysis- III
Method
M=N-B–C
δM = (N + δB2 + δC2)1/2
Assumptions
Th/U = 3.9 ; C model
MKL= MBX
Combined result:
consistent w/ GP, GC
weakly excludes CC
Rmantle = 17 ± 10 TNU
Weighted average
BX > KL
but consistent
with BX=KL
Dye, 2012
arXiv:1111.6099v2
Sramek et al., 2012
Gν Analysis- III
KamLAND (2011) data
consistent with models,
prefers Mh < Aq
Borexino (2010) data
consistent with GP and
Mh = Aq
KL+BX (weighted averages)
consistent w/ GP & GC
weakly exclude CC
Min Mh = 28 ± 13 TW
Max Mh = 33 ± 16 TW
Dye, 2012
arXiv:1111.6099v2
Homogeneous
mantle
DM w/ enriched
basement layer
Resolving Geological Models- Prospects
Crust systematic
dominates rate
uncertainty
Single measurement
at continental or
existing site does
not resolve models
Single measurement
at oceanic site does
resolve models
Dye, 2012
arXiv:1111.6099v2
Expected Signals: Existing Sites
KL before and after
reactor shutdown
BX can operate for many years before
systematic uncertainty significant
Expected Signals: Future & Prospective Sites
Continental Observatories
Next year!!!
+ Baksan
Mount
Elbrus
43° 14’ N
42° 41’ E
Village
Neutrino
Oceanic Observatory
Geo-neutrino Observatory Network
Pyhäsalmi
Baksan
Homestake
Sramek et al., 2012
• Borexino
Project Updates
– “… 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
• LENA
– White paper published in Astropart. Phys.- M. Wurm
• Baksan
– Discussing 10-50 kT detector- V. Sinev
• Hanohano
– Discussing 2-3 kT GeoPANO
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
GeoPANO : 3 TNU-1 δm = ± 3 TNU
GeoPANO : 6 TNU-1 δm = ± 2 TNU
OR
Network- Five x 10 TNU-1 δm = ± 3 TNU
Gν Summary
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Observing planetary U & Th; no K or direction
Data accumulating in two geo-ν detectors: KL & BX
Beginning to address geological models
SNO+ next year!
– First continental observatory
– 5-y statistical error ±6 TNU (~12% Gν measurement)
– First measurement of Th/U
• Oceanic observatory resolves geological models
• Model resolution possible with network of continental
observatories
– SNO+, LENA, Baksan, Homestake, plus KL & BX