Transcript A Deep Ocean Anti-Neutrino Observatory

A Deep Ocean Anti-Neutrino
Observatory
An Introduction to the Science
Potential of Hanohano
Presented by
Steve Dye
University of Hawaii at Manoa
Hawaii Pacific University
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Outline
• Neutrino Geophysics
– U/Th mantle flux
– Th/U ratio
– Geo-reactor search
• Neutrino Oscillation Physics
– Mixing angles θ12 and θ13
– Mass squared difference Δm231
– Mass hierarchy
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Hawaii Anti-Neutrino Observatory†
Location flexibility
– Far from continental crust and reactors
for neutrino geophysics- Hawaii
– Offshore of reactor for neutrino
oscillation physics- California, Taiwan
*
Technological issues being addressed
– Scintillating oil studies: P=450 atm., T=0°C
– Implosion studies at sea
– Engineering studies of detector structure,
deployment
† hanohano- Hawaiian for distinguished
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Hanohano- 10x “KamLAND” in ocean
Construct in shipyard, fill/test in port, tow to site, and submerge to ~4 km
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Preliminary reference Earth model
Knowledge of Earth interior from seismology
Dziewonski and Anderson, Physics of the Earth and Planetary Interiors 25 (1981) 297-356.
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Bulk silicate Earth model
Knowledge of Earth
composition largely
model dependent.
“Standard Model” based
on 3 meteorite samples.
McDonough and Sun, Chemical Geology 120 (1995) 223-253.
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Terrestrial heat flow: 31-44 TW
Present controversy over hydrothermal flow
Pollack, Hurter, and Johnson, Reviews of Geophysics 31(3) (1993) 267-280.
Hofmeister and Criss, Tectonophysics 395 (2005) 159-177.
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Geo-neutrinos- parent spectrum
thorium chain
uranium chain
prompt
Threshold for Reines and Cowan
coincidence technique
No direction or K neutrinos yet
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delayed
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Predicted geo-neutrino signal
Hanohano
SNO+
Borexino
KamLAND
F. Mantovani et al., Phys. Rev. D 69 (2004) 013001.
Crust dominates on continents
Mantle dominates in ocean
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Simulated event source distribution
Signal mostly from <500 km 9
Geo-ν + background spectra
Background manageable
μ±
μ±
Cosmic ray muons
Target
Volume
alpha
source
spallation
products
fast neutrons
Radioactive materials
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Hanohano: mantle measurement
1 year of Hanohano
15 years of SNO+
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48 years of Borexino
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Hanohano: mantle measurement
Mantle (ev / 10 kT-y)
400
300
20% in 1 year
200
100
0
-100
KLND
SNO+
Bxno
Hano
-200
-300
Hanohano has ultimate sensitivity of <10%. Continental
detectors cannot measure the mantle flux to better than 50%.
Limiting factor 20% systematic uncertainty in U/Th content.
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Earth Th/U ratio measurement
Project
crust type
δR/R
(1 yr exposure)
Th/U
(1 yr exposure)
Years to 10%
measurement
KamLAND
island arc
2.0
4±8
390
Borexino
continental
1.1
4±4
120
SNO+
continental
0.62
3.9 ± 2.4
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Hanohano
oceanic
0.20
3.9 ± 0.8
3.9
Statistical uncertainties only; includes reactors
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Anti-neutrinos from the core?
Herndon hypothesis- natural
fission reactor in core of Earth
P=1-10 TW
Controversial but not ruled out
Geo-reactor hypothesis
Herndon, Proc. Nat. Acad. Sci. 93 (1996) 646.
Hollenbach and Herndon, Proc. Nat. Acad. Sci. 98 (2001) 11085.
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Geo-reactor power (TW)
Geo-reactor search
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Project
crust type
Power limit
99% CL
(TW)
5σ discovery
power
(TW)
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KamLAND
island arc
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51
10
Borexino
continental
12
43
5
SNO+
continental
9
22
0
Hanohano
oceanic
0.3
1.0
Power upper limit
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KL
Bxno
SNO+
Hano
~few TW needed to
drive geomagnetic field
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1 year run timestatistical uncertainties only
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3-ν mixing: Reactor neutrinos
Pee=1-{cos4(θ13)sin2(2θ12)sin2(Δm221L/4E)
+cos2(θ12)sin2(2θ13)sin2(Δm231L/4E)
+sin2(θ12)sin2(2θ13)sin2(Δm232L/4E)}
Each amplitude cycles with own frequency
• ½-cycle measurements
– mixing angles, mass-squared differences
• Multi-cycle measurements
– Mixing angles, mass-squared differences
– Potential for mass hierarchy
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Reactor ν mixing parameters:
present knowledge
• KamLAND combined analysis:
tan2(θ12)=0.40(+0.10/–0.07)
Δm221=(7.9±0.7)×10-5 eV2
Araki et al., Phys. Rev. Lett. 94 (2005) 081801.
• CHOOZ limit: sin2(2θ13) ≤ 0.20
Apollonio et al., Eur. Phys. J. C27 (2003) 331-374.
• SuperK and K2K:
Δm231=(2.5±0.5)×10-3 eV2
Ashie et al., Phys. Rev. D64 (2005) 112005
Aliu et al., Phys. Rev. Lett. 94 (2005) 081802
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νe flux measurement uncertainty
• Flux from distant, extended source like
Earth or sun is fully mixed
• P(νe→νe)
=1-0.5{cos4(θ13)sin2(2θ12)+sin2(2θ13)}
=0.592 (+0.035/-0.091)
Lower value for maximum angles
Upper value for minimum angles
• Φsource= Φdetector/P(νe→νe)
Uncertainty is +15%/-6%
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Suggested ½-cycle θ12 measurement
• Reactor experiment- νe point source
• P(νe→νe)≈1-sin2(2θ12)sin2(Δm221L/4E)
• 60 GW·kT·y exposure at 50-70 km
– ~4% systematic error from near detector
– sin2(θ12) measured with ~2% uncertainty
Bandyopadhyay et al., Phys. Rev. D67 (2003) 113011.
Minakata et al., hep-ph/0407326
Bandyopadhyay et al., hep-ph/0410283
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Proposed ½-cycle θ13 measurements
• Reactor experiment- νe point source
• P(νe→νe)≈1-sin2(2θ13)sin2(Δm231L/4E)
• Double Chooz, Daya Bay, Reno- measure
θ13 with “identical” near/far detector pair
– sin2(2θ13)≤0.03-0.01 in few years
– Solar and matter insensitive
– Challenging systematics
Mikaelyan and Sinev, Phys. Atom. Nucl. 62 (1999) 2008-2012.
Anderson et al., hep-ex/0402041
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Reactor antineutrino spectra- 50 km
Plots by jgl
no oscillation
no oscillation
Distance/energy,
L/E
Energy, E
oscillations
oscillations
Neutrino energy (MeV)
L/E (km/MeV)
1,2 oscillations with sin2(2θ12)=0.82 and Δm221=7.9x10-5 eV2
1,3 oscillations with sin2(2θ13)=0.10 and Δm231=2.5x10-3 eV2
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Fourier Transform on L/E to Δm2
Plots by jgl
Fourier Power, Log Scale
Δm232 < Δm231
normal hierarchy
Peak due to
nonzero θ13
Spectrum w/ θ13=0
Δm2 (x10-2 eV2)
Δm2/eV2
Includes energy smearing- 3.5%/√E
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Preliminary10 kt-y exposure at 50 km range
sin2(2θ13)≥0.05
Δm231=0.0025 eV2 to % level
Learned, Pakvasa, Svoboda, SD preprint in
preparation
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Neutrino mass hierarchy- reactor neutrinos
m3
mass
m2
m1
m2
m1
Exposure and energy
resolution are critical
inverted
for this determination
|Δm231| < |Δm232| are currently under study
m3
normal
|Δm231| > |Δm232|
Δm232 ≈ (1.00 ± 0.03) Δm231
Petcov and Piai, Phys. Lett. B533 (2001) 94-106.
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Hanohanocandidate reactor sites
San Onofre- ~6 GWth
Maanshan- ~5 GWth
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Hanohano- 10 kT-y exposure
• Neutrino Geophysics- near Hawaii
– Mantle flux U/Th geo-neutrinos to ~25%
– Measure Th/U ratio to ~20%
– Rule out geo-reactor of P>0.3 TW
• Neutrino Oscillation Physics- ~60 km by reactor
–
–
–
–
Measure sin2 (θ12) to few % w/ standard ½-cycle
Measure sin2(2θ13) down to ~0.05 w/ multi-cycle
Δm231 at percent level w/ multi-cycle
potential for mass hierarchy if θ13>0 without near
detector; insensitive to background, systematics;
complimentary to Minos, Nova
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Conclusion
• Hanohano
– 10 kT deep ocean anti-neutrino observatory
– Movable for multi-disciplinary science
• Neutrino geophysics
• Neutrino oscillation physics
– Under development at Hawaii; continuing
funding from U.S. Department of Defense
– 1st collaboration meeting 3/07
Interested? [email protected]
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