Hanohano

1. Hanohano Mikhail Batygov, University of Hawaii. Brookhaven, UDiG workshop, October 17, 2008

2. Overview of the project goals • Main goals of the project • Fundamental physics, esp.  oscillation studies • Terrestrial antineutrinos • Special advantages • Reduced sensitivity to systematics • Combination of big size and low energy threshold • Variable baseline option • Additional studies • Nucleon decay, possibly incl. SUSY favored kaon mode • Supernova detection • Relic SN neutrinos • Demonstration of remote reactor monitoring • Special interest for nuclear non-proliferation

3. Oscillation Parameters: present • KamLAND (with SNO) analysis: sin2(θ12)=0.82±0.4 Δm221=(7.6±0.2)×10-5 eV2 SuperK, K2K, MINOS: Δm2atm=(2.41±0.13)×10-3 eV2 CHOOZ limit: sin2(2θ13) ≤ 0.20

4. 3- mixing Pee=1-{ cos4(θ13) sin2(2θ12) [1-cos(Δm212L/2E)] + cos2(θ12) sin2(2θ13) [1-cos(Δm213L/2E)] + sin2(θ12) sin2(2θ13) [1-cos(Δm223L/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 (Δm212) and ~4 km (Δm213~Δm223) 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 exposure • Multi-cycle measurements can yield • Mixing angles, precise mass-squared differences • Mass hierarchy • Less sensitive to systematic errors

5. Origin of geo-neutrinos Two types of crust: Oceanic & Continental • Generated in -decays of radioactive isotopes from 238U and 232Th decay series • Crust believed to be the primary source of geo-neutrinos for land-based experiments Oceanic crust: single stage melting of the mantle Continental crust: multi-stage melting processes Compositionally distinct

6. Predicted Geoneutrino Flux Continental detectors dominated by continental crust geo-neutrinos Oceanic detectors can probe the U/Th contents of the mantle Reactor Flux - irreducible background Geoneutrino flux determinations -continental (DUSEL, SNO+, LENA) -oceanic (Hanohano)

7. Hanohano: engineering studies Makai Ocean Engineering • 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 Barge 112 m long x 23.3 wide For  oscillation 2 possible locations: near Taiwan and near California Deployment Sketch Descent/ascent 39 min

8. Expected performance in  oscillation studies • Systematic uncertainties were considered • Effect of geo-neutrino background taken into account (turned out greater than expected!) • Goals • Study expected sensitivities to measurable oscillation parameters • Determine optimal baselines • Formulate technical requirements to the detector • Study carried out with Hanohano in mind but results applicable to any similar experiment, ocean-based or land-based

9. Simulation assumptions • Detector size: about 10 kT of LS • Detector energy resolution: 2.5%sqrt(Evis) • State of the art by today’s standards but possible; work is in progress at UHM • Terrestrial antineutrino flow: about 30 TNU but not known exactly (unconstrained) • Detector systematics: • 2% in expected event rate • 8% in energy resolution estimation • 1% in “linear” energy scale uncertainty

10. Expected sensitivity to “solar” oscillation parameters sin2212 m212 • Geo-neutrinos are an issue • Not sensitive to detector resolution and systematics • Can achieve 0.01 accuracy in sin2212 in ~300 GWtkTy • Can achieve 1% in m212 in ~300 GWtkTy “pessimistic: systematics unconstrained” default systematics “optimistic”: no detector systematics no systematics, no geo-

11. Expected sensitivity to 13 • Moderately sensitive to resolution (more for longer baselines) and systematics (more for shorter baselines) • Geo-neutrinos not an issue • Target sensitivity 0.02 in sin2213 and will probably be exceeded in 300 GWtkTy • Optimum baselines < 30 km “pessimistic: systematics unconstrained” default systematics “optimistic”: no detector systematics no systematics, no geo-

12. Expected sensitivity to m212 and m213 “pessimistic: systematics unconstrained” • Very demanding of detector energy resolution • Two families of solutions, for each hierarchy respectively, one somewhat favored over another • Sensitivity depends on sin2213 • Optimum baselines ~< 30 km default systematics “optimistic”: no detector systematics no systematics, no geo- Note: for sin2213=0.05

13. Expected sensitivity to  mass hierarchy “pessimistic: systematics unconstrained” • Extremely demanding of detector resolution • Success depends on the actual value of 13; unlikely to achieve considerable CL if sin2213 less than 0.05 • Optimum baselines ~50 km default systematics “optimistic”: no detector systematics no systematics, no geo- Note: for sin2213=0.05 Note: for sin2213=0.05

14. Conclusions • No  oscillation studies appear to be systematically constrained at medium baselines • Multi-baseline exposure offers better overall performance; Hanohano can take advantage of its movability; land-based experiment would be better suited with several smaller detectors at different baselines • Geo-neutrinos are a handicap for solar parameter measurement • Useful estimations of geo-neutrino flux can still be performed even in the presence of reactor background • Big underwater detector offers real opportunity to measure in 300 GWtkTy: • Solar parameters to 1% (currently – 3-5%) • sin2213 to 2% (competitive with dedicated experiments but complimentary due to being constrained statistically rather than systematically) • Atmospheric m2: depends on sin2213 but may be below 1% if sin2213 > 0.05 • Mass hierarchy: unlikely unless sin2213 > 0.05 but may be possible with bigger multi-baseline setups