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Hanohano
Mikhail Batygov,University of Hawaii,
October 4, 2007, Hamamatsu, Japan, NNN’07
Overview of the project Dual goal of the project
Fundamental physics, esp. oscillation studies Terrestrial antineutrinos
Special advantages Reduced sensitivity to systematics Big size and low energy threshold Variable baseline possible
Additional studies Nucleon decay, possibly incl. SUSY favored kaon mode Supernova detection Relic SN neutrinos
Oscillation Parameters: present
KamLAND (with SNO) analysis:tan2(θ12)=0.40(+0.10/–0.07)Δm2
21=(7.9+0.4/-0.35)×10-5 eV2
Araki et al., Phys. Rev. Lett. 94 (2005) 081801. (improved in 2007)
SuperK, K2K, MINOS: Δm2
31=(2.5±0.5)×10-3 eV2
Ashie et al., Phys. Rev. D64 (2005) 112005Aliu et al., Phys. Rev. Lett. 94 (2005) 081802 (improved in 2007)
CHOOZ limit: sin2(2θ13) ≤ 0.20Apollonio et al., Eur. Phys. J. C27 (2003) 331-374.
Oscillation parameters to be measured
Precision measurement of mixing parameters needed
World effort to determine θ13 (= θ31)
Determination of mass hierarchy
2 mass diffs, 3 angles, 1 CP phase2 mass diffs, 3 angles, 1 CP phase
12 precise measurement (2 mixing)
Reactor experiment- ν e point source
P(νe→νe)≈1-sin2(2θ12)sin2(Δm2
21L/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/0407326Bandyopadhyay et al., hep-ph/0410283
Ideal spot
3- mixingPee=1-{ cos4(θ13) sin2(2θ12) [1-cos(Δm2
12L/2E)] + cos2(θ12) sin2(2θ13) [1-cos(Δm2
13L/2E)] + sin2(θ12) sin2(2θ13) [1-cos(Δm2
23L/2E)]}/2
Survival probability: 3 oscillating terms each cycling in L/E space (~t) with own “periodicity” (Δm2~ω)
Amplitude ratios ~13.5 : 2.5 : 1.0 Oscillation lengths ~110 km (Δm2
12) and ~4 km (Δm213 ~ Δm2
23) at reactor peak ~3.5 MeV
Two possible approaches: ½-cycle measurements can yield
Mixing angles, mass-squared differences Less statistical uncertainty for same parameter and detector
Multi-cycle measurements can yield Mixing angles, precise mass-squared differences Mass hierarchy Less sensitive to systematic errors
Reactor Reactor ννee Spectra at 50 Spectra at 50 kmkm
1,2 oscillations with sin2(2θ12)=0.82 and Δm2
21=7.9x10-5 eV2
1,3 oscillations with sin2(2θ13)=0.10 and
Δm231=2.5x10-3 eV2
no oscillation
oscillations
no oscillation
oscillations
Neutrino energy (MeV) L/E (km/MeV)
Distance/energy, Distance/energy, L/EL/E
Energy, EEnergy, E
> 15 cycles
invites use of Fourier Transforms
Fourier Transform on L/E to Fourier Transform on L/E to ΔΔmm22
Fourier Power, Log Scale
Spectrum w/ θ13=0
Δm2/eV2
Preliminary-50 kt-y exposure at 50 km range
sin2(2θ13)≥0.02 Δm2
31=0.0025 eV2 to 1% level
Learned, Dye,Pakvasa, Svoboda hep-ex/0612022
Δm232 < Δm2
31 normal hierarchy
Δm2 (x10-2 eV2)
0.0025 eV2 peak due to nonzero θ13
Includes energy smearing
Peak profile versus distance
E smearing
Fewer cycles
50 km
Measure Measure ΔΔmm223131 by Fourier by Fourier
Transform & Determine Transform & Determine νν Mass Mass HierarchyHierarchy
Determination at ~50 km range
sin2(2θ13)≥0.05 and 10 kt-y
sin2(2θ13)≥0.02 and 100 kt-yΔm2 (x10-2 eV2)Plot by jgl
Δm231 > Δm2
32 |Δm231| < |Δm2
32|
normalinverted
Learned, Dye, Pakvasa, and Svoboda, hep-ex/0612022
θ12<π/4!
Distance variation: 30, 40, 50, 60 km
Hierarchy DeterminationHierarchy DeterminationIdeal Case with 10 kiloton Detector, 1 year off San Onofre
Sin22θ13 Variation: 0.02 – 0.2
100 kt-yrs separates even at 0.02
Normal Hierarchy
Invertedhierarchy
Hierarchy tests employing Matched filter technique, for Both normal and inverted hierarchy on each of 1000 simulated one year experiments using 10 kiloton detector.
Sensitive to energy resolution: Simulation for 3%/sqrt(E)
30 km
60 km
sin22 = 0.02
0.2
Inv.
Norm.
Effect of Energy Resolution
Uses the difference in spectra Efficiency depends heavily on energy resolution
Perfect E resolution E = 6%*sqrt(Evis)
E, MeV E, MeV
Estimation of the statistical significance
Thousands of events necessary for reliable discrimination – big detector needed Longer baselines more sensitive to energy resolution; may be beneficial to adjust for
actual detector performance
Detector energy resolution, MeV0.5
Neu
trin
o ev
ents
to
1
CL
KamLAND: 0.065 MeV0.5
< 3%: desirable but maybe unrealistic E resolution
Big picture questions in Earth ScienceBig picture questions in Earth Science
What drives plate tectonics?
What is the Earth’s energy budget?
What is the Th & U conc. of the Earth?
Energy source driving the Geodynamo? Geo- reactor?
Data sources
Earth’s Total Heat FlowEarth’s Total Heat Flow
• Conductive heat flow measured from bore-hole temperature gradient and conductivity
Total heat flow Conventional view 44441 TW1 TW Challenged recently 31311 TW - ?1 TW - ?What is the origin of the heat?
Radiogenic heat and geo-Radiogenic heat and geo-neutrinosneutrinos
238U (“Radium”)-decay chain
Th-decay chain
40K-decay modes
n p + e- + e
Detectable>1.8 MeV
2 more decay chains:235U “Actinium” – no -decays with sufficient energy“Neptunium” – extinct by now
Mantle convection models typically assume:mantle Urey ratio: 0.4 to 1.0, generally ~0.7
Geochemical models predict: Urey ratio 0.4 to 0.5.
Urey Ratio and Urey Ratio and Mantle Convection Mantle Convection ModelsModels
Urey ratio =radioactive heat production
heat loss
Discrepancies?Discrepancies? Est. total heat flow, 44 or 31TW est. radiogenic heat production 16TW or 31TW Where are the problems?
Mantle convection models? Total heat flow estimates? Estimates of radiogenic heat production rate?
Geoneutrino measurements can constrain the planetary radiogenic heat production.
U and Th DistributionU and Th Distributionin the Earthin the Earth U and Th are thought to be absent from the core and
present in the mantle and crust. Core: Fe-Ni metal alloy Crust and mantle: silicates
U and Th concentrations are the highest in the continental crust. Continents formed by melting of the mantle. U and Th prefer to enter the melt phase
Continental crust: insignificant in terms of mass but major Continental crust: insignificant in terms of mass but major reservoir for U, Th, K.reservoir for U, Th, K.
Two types of crust: Oceanic & ContinentalTwo types of crust: Oceanic & Continental
Oceanic crust: single stage melting of the mantleContinental crust: multi-stage melting processes Compositionally distinct
Predicted Predicted Geoneutrino FluxGeoneutrino Flux
Geoneutrino flux determinations-continental (DUSEL, SNO+, LENA)-oceanic (Hanohano)
Reactor FluxReactor Flux - irreducible background
Continental detectors dominated by continental crust geo-neutrinosOceanic detectors can probe the U/Th contents of the mantle
Current status of geo-neutrino studies 2005: KamLAND detected terrestrial antineutrinos Result consistent with wide range of geological
models; most consistent with 16 TW radiogenic flux
2007: KamLAND updated geo-neutrino result Still no reasonable models can be ruled out KamLAND limited by reactor background; future
geo-neutrino detector must be built further from reactors
Requirements to the detector Baseline on the order of 50 km; better variable for
different studies Big number of events (large detector) For Hierarchy and m2
13/23: Good to excellent energy resolution sin2(213) 0 No full or nearly full mixing in 12 (almost assured by SNO
and KamLAND) For Geo-neutrinos: ability to “switch off” reactor
background To probe the geo-neutrino flux from the mantle:
ocean based
Anti-Neutrino Detection mechanism: inverse
Evis=Eν-0.8 MeVprompt
delayedEvis=2.2 MeV
• Standard inverse β-decay coincidence
• Eν > 1.8 MeV
• Rate and precise spectrum; no direction
Production in reactorsand natural decays
Detection
Key: 2 flashes, close in space and time, 2 flashes, close in space and time, 22ndnd of known energy, of known energy, eliminate backgroundeliminate background
Reines & Cowan
Deployment Sketch
Hanohano: Hanohano: engineering studiesengineering studies
Studied vessel design up to 100 kilotons, based upon cost, stability, and construction ease.
Construct in shipyard Fill/test in port Tow to site, can traverse Panama Canal Deploy ~4-5 km depth Recover, repair or relocate, and redeploy
Descent/ascent 39 min
Barge 112 m long x 23.3 wide
Makai Ocean Engineering
Addressing Technology Addressing Technology IssuesIssues
Scintillating oil studies in lab P=450 atm, T=0°C Testing PC, PXE, LAB and
dodecane No problems so far, LAB
(Linear AlkylBenzene) favorite… optimization underway
Implosion studies Design with energy absorption Computer modeling & at sea No stoppers
Power and comm, no problems PMT housing: Benthos glass boxes Optical detector, prototypes OK Need second round design
20m x 35mfiducial vol.
1 m oil
2m pure water
Current status Several workshops held (’04, ’05, ’06) and ideas
developed Study funds provided preliminary engineering and
physics feasibility report (11/06) Strongly growing interest in geology community Work proceeding and collaboration in formation Upcoming workshops in Washington DC (10/07)
and Paris (12/07) for reactor monitoring Funding request for next stage (’06) in motion Ancillary proposals and computer studies
continue
Summary Better precision for sin2(212), sin2(213) – to 2%
possible with Hanohano If sin2(213) 0: high precision measurement of
m213, m2
23, and even mass hierarchy possible with the same detector; for sin2212 = 0.05, m2
13, m223 –
to 1-2% (0.025-0.05x10-3 eV2) Big ocean based detector is perfect for oscillation
studies (adjustable baseline, high accuracy) and for studying geo-neutrinos, especially from the mantle
Geo-reactor hypothesis can be ultimately tested Additional physics measurements achievable to
higher precision than achieved before
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