Hanohano

Mikhail Batygov,University of Hawaii.

Brookhaven, UDiG workshop,October 17, 2008

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

Oscillation Parameters: present

• KamLAND (with SNO) analysis:sin2(θ12)=0.82±0.4Δm2

21=(7.6±0.2)×10-5 eV2

SuperK, K2K, MINOS: Δm2

atm=(2.41±0.13)×10-3 eV2

CHOOZ limit: sin2(2θ13) ≤ 0.20

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 (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 exposure

• Multi-cycle measurements can yield– Mixing angles, precise mass-squared differences– Mass hierarchy– Less sensitive to systematic errors

Origin of geo-neutrinosOrigin of geo-neutrinos

Oceanic crust: single stage melting of the mantleContinental crust: multi-stage melting processes Compositionally distinct

Two types of crust: Oceanic & ContinentalTwo 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

Predicted Geoneutrino FluxPredicted Geoneutrino 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

Deployment Sketch

Hanohano: engineering Hanohano: engineering studiesstudies

• 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

For oscillation 2 possible locations: near Taiwan and near California

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

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

Expected sensitivity to “solar” oscillation parameters

• Geo-neutrinos are an issue• Not sensitive to detector resolution and systematics• Can achieve 0.01 accuracy in sin2212 in ~300 GWtkTy• Can achieve 1% in m2

12 in ~300 GWtkTy

sin2212 m212

“pessimistic: systematics unconstrained”

default systematics

“optimistic”: no detector systematics

no systematics, no geo-

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 sin2213 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-

Expected sensitivity to m212 and

m213

• Very demanding of detector energy resolution

• Two families of solutions, for each hierarchy respectively, one somewhat favored over another

• Sensitivity depends on sin2213

• Optimum baselines ~< 30 km

Note: for sin2213=0.05

“pessimistic: systematics unconstrained”

default systematics

“optimistic”: no detector systematics

no systematics, no geo-

Expected sensitivity to mass hierarchy

• Extremely demanding of detector resolution• Success depends on the actual value of 13; unlikely to achieve considerable CL if

sin2213 less than 0.05• Optimum baselines ~50 km

Note: for sin2213=0.05Note: for sin2213=0.05

“pessimistic: systematics unconstrained”

default systematics

“optimistic”: no detector systematics

no systematics, no geo-

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%)– sin2213 to 2% (competitive with dedicated experiments but complimentary due to

being constrained statistically rather than systematically)– Atmospheric m2: depends on sin2213 but may be below 1% if sin2213 > 0.05– Mass hierarchy: unlikely unless sin2213 > 0.05 but may be possible with bigger

multi-baseline setups