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: tan 2 (θ 12 ) = 0.40( / – 0.07) Δm 2 21 =( /-0.35) × eV 2 Araki et al., Phys. Rev. Lett. 94 (2005) (improved in 2007)  SuperK, K2K, MINOS: Δm 2 31 =(2.5 ± 0.5) × eV 2 Ashie et al., Phys. Rev. D64 (2005) Aliu et al., Phys. Rev. Lett. 94 (2005) (improved in 2007)  CHOOZ limit: sin 2 (2θ 13 ) ≤ 0.20 Apollonio et al., Eur. Phys. J. C27 (2003)

Oscillation parameters to be measured  Precision measurement of mixing parameters needed  World effort to determine θ 13 (= θ 31 )  Determination of mass hierarchy 2 mass diffs, 3 angles, 1 CP phase

 12 precise measurement (2 mixing)  Reactor experiment- ν e point source  P( ν e → ν e ) ≈ 1- sin 2 (2 θ 12 )sin 2 (Δ m 2 21 L /4 E )  60 GW·kt·y exposure at km ~4% systematic error from near detector sin 2 ( θ 12 ) measured with ~2% uncertainty Bandyopadhyay et al., Phys. Rev. D67 (2003) Minakata et al., hep-ph/ Bandyopadhyay et al., hep-ph/ Ideal spot

3- mixing P ee = 1-{ cos 4 (θ 13 ) sin 2 (2θ 12 ) [1-cos(Δm 2 12 L/2E)] + cos 2 (θ 12 ) sin 2 (2θ 13 ) [1-cos(Δm 2 13 L/2E)] + sin 2 (θ 12 ) sin 2 (2θ 13 ) [1-cos(Δm 2 23 L/2E)]}/2  Survival probability: 3 oscillating terms each cycling in L/E space (~t) with own “periodicity” (Δm 2 ~ω) Amplitude ratios ~13.5 : 2.5 : 1.0 Oscillation lengths ~110 km (Δm 2 12 ) and ~4 km (Δm 2 13 ~ Δm 2 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 ν e Spectra at 50 km 1,2 oscillations with sin 2 (2θ 12 )=0.82 and Δm 2 21 =7.9x10 -5 eV 2 1,3 oscillations with sin 2 (2θ 13 )=0.10 and Δm 2 31 =2.5x10 -3 eV 2 no oscillation oscillations no oscillation oscillations Neutrino energy (MeV)L/E (km/MeV) Distance/energy,L/E Energy, E > 15 cycles invites use of Fourier Transforms

Fourier Transform on L/E to Δm 2 Fourier Power, Log Scale Spectrum w/ θ 13 =0 Δm 2 /eV 2 Preliminary- 50 kt-y exposure at 50 km range sin 2 (2θ 13 )≥0.02 Δm 2 31 = eV 2 to 1% level Learned, Dye,Pakvasa, Svoboda hep-ex/ Δm 2 32 < Δm 2 31 normal hierarchy Δm 2 (x10 -2 eV 2 ) eV 2 peak due to nonzero θ 13 Includes energy smearing Peak profile versus distance E smearing Fewer cycles 50 km

Measure Δm 2 31 by Fourier Transform & Determine ν Mass Hierarchy Determination at ~50 km range sin 2 (2θ 13 )≥0.05 and 10 kt-y sin 2 (2θ 13 )≥0.02 and 100 kt-y Δm 2 (x10 -2 eV 2 ) Plot by jgl Δm 2 31 > Δm 2 32 |Δm 2 31 | < |Δm 2 32 | normal inverted Learned, Dye, Pakvasa, and Svoboda, hep-ex/ θ 12 <π/4!

Distance variation: 30, 40, 50, 60 km Hierarchy Determination Ideal Case with 10 kiloton Detector, 1 year off San Onofre Sin 2 2θ 13 Variation: 0.02 – kt-yrs separates even at 0.02 Normal Hierarchy Inverted hierarchy 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 sin 2 2  = Inv. Norm.

Effect of Energy Resolution  Uses the difference in spectra  Efficiency depends heavily on energy resolution Perfect E resolution  E = 6%*sqrt(E vis ) 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, MeV 0.5 Neutrino events to 1  CL KamLAND: MeV 0.5 < 3%: desirable but maybe unrealistic E resolution

Big 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 Flow Conductive heat flow measured from bore- hole temperature gradient and conductivity Total heat flow Conventional view 44  1 TW Challenged recently 31  1 TW - ? What is the origin of the heat?

Radiogenic heat and geo-neutrinos 238 U (“Radium”)-decay chain Th-decay chain 40 K-decay modes n p + e - + e Detectable >1.8 MeV 2 more decay chains: 235 U “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 Mantle Convection Models Urey ratio = radioactive heat production heat loss

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 Distribution in 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 reservoir for U, Th, K.

Two types of crust: Oceanic & Continental Oceanic crust: single stage melting of the mantle Continental crust: multi-stage melting processes Compositionally distinct

Predicted Geoneutrino Flux Geoneutrino flux determinations -continental (DUSEL, SNO+, LENA) -oceanic (Hanohano) Reactor Flux Reactor Flux - irreducible background Continental detectors dominated by continental crust geo- neutrinos Oceanic 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 m 2 13/23 : Good to excellent energy resolution sin 2 (2 13 )  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  E vis =E ν -0.8 MeV prompt delayed E vis =2.2 MeV Standard inverse β-decay coincidence E ν > 1.8 MeV Rate and precise spectrum; no direction Production in reactors and natural decays Detection 2 flashes, close in space and time, Key: 2 flashes, close in space and time, 2 nd of known energy, eliminate background Reines & Cowan

Deployment Sketch Hanohano: engineering 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 Issues  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 35m fiducial 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 sin 2 (2 12 ), sin 2 (2 13 ) – to 2% possible with Hanohano  If sin 2 (2 13 )  0: high precision measurement of m 2 13, m 2 23, and even mass hierarchy possible with the same detector; for sin 2 2 12 = 0.05, m 2 13, m 2 23 – to 1-2% ( x10 -3 eV 2 )  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