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