Transcript Δm 2

Hanohano
Mikhail Batygov,
University of Hawaii,
October 4, 2007,
Hamamatsu, Japan, NNN’07
Overview of the project
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Dual goal of the project
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Special advantages
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Fundamental physics, esp.  oscillation studies
Terrestrial antineutrinos
Reduced sensitivity to systematics
Big size and low energy threshold
Variable baseline possible
Additional studies
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Nucleon decay, possibly incl. SUSY favored kaon mode
Supernova detection
Relic SN neutrinos
Oscillation Parameters: present
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KamLAND (with SNO)
analysis:
tan2(θ12)=0.40(+0.10/–0.07)
Δm221=(7.9+0.4/-0.35)×10-5 eV2
Araki et al., Phys. Rev. Lett. 94 (2005)
081801. (improved in 2007)
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SuperK, K2K, MINOS:
Δm231=(2.5±0.5)×10-3 eV2
Ashie et al., Phys. Rev. D64 (2005)
112005
Aliu et al., Phys. Rev. Lett. 94 (2005)
081802 (improved in 2007)
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CHOOZ limit: sin2(2θ13) ≤ 0.20
Apollonio et al., Eur. Phys. J. C27 (2003) 331374.
Oscillation parameters to be measured
2 mass diffs, 3 angles, 1 CP phase
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Precision measurement
of mixing parameters needed
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World effort to determine θ13 (= θ31)
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Determination of mass hierarchy
12 precise measurement (2 mixing)
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Reactor experiment- ν e
point source
P(νe→νe)≈1sin2(2θ12)sin2(Δm221L/4E)
60 GW·kt·y exposure at
50-70 km
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~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/0407326
Bandyopadhyay et al., hep-ph/0410283
Ideal spot
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
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Survival probability: 3 oscillating terms each cycling in L/E space
(~t) with own “periodicity” (Δm2~ω)
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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:
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½-cycle measurements can yield
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Mixing angles, mass-squared differences
Less statistical uncertainty for same parameter and detector
Multi-cycle measurements can yield
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Mixing angles, precise mass-squared differences
Mass hierarchy
Less sensitive to systematic errors
Reactor νe Spectra at 50 km
invites use of Fourier Transforms
Distance/energy,
L/E
Energy, E
no oscillation
no oscillation
> 15 cycles
oscillations
Neutrino energy (MeV)
oscillations
L/E (km/MeV)
1,2 oscillations with sin2(2θ12)=0.82 and Δm221=7.9x10-5 eV2
1,3 oscillations with sin2(2θ13)=0.10 and Δm231=2.5x10-3 eV2
Fourier Transform on L/E to Δm2
Fourier Power, Log Scale
Δm232 < Δm231
normal hierarchy
Peak profile versus distance
E smearing
0.0025 eV2
peak due to
nonzero θ13
Spectrum w/ θ13=0
50 km
Fewer cycles
Δm2 (x10-2 eV2)
Δm2/eV2
Includes energy smearing
Preliminary50 kt-y exposure at 50 km range
sin2(2θ13)≥0.02
Δm231=0.0025 eV2 to 1% level
Learned, Dye,Pakvasa, Svoboda hep-ex/0612022
Measure Δm231 by Fourier Transform &
Determine ν Mass Hierarchy
inverted
normal
Δm231 > Δm232
θ12<π/4!
|Δm231| < |Δm232|
Determination at ~50 km range
sin2(2θ13)≥0.05 and 10 kt-y
Plot by jgl
Δm2 (x10-2 eV2)
sin2(2θ13)≥0.02 and 100 kt-y
Learned, Dye, Pakvasa, and Svoboda, hep-ex/0612022
Hierarchy Determination
Ideal Case with 10 kiloton Detector, 1 year off San Onofre
Distance variation: 30, 40, 50, 60 km
Inverted
hierarchy
Hierarchy tests employing
Matched filter technique, for
Inv.
Both normal and inverted
hierarchy on each of 1000
simulated one year experiments
using 10 kiloton detector.
Norm.
Sin22θ13 Variation: 0.02 – 0.2
Normal Hierarchy
sin22 = 0.02
30 km
100 kt-yrs separates
even at 0.02
Sensitive to energy resolution:
Simulation for 3%/sqrt(E)
0.2
60 km
Effect of Energy Resolution
Perfect E resolution
E, MeV
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E = 6%*sqrt(Evis)
E, MeV
Uses the difference in spectra
Efficiency depends heavily on energy resolution
Neutrino events to 1  CL
Estimation of the statistical significance
< 3%: desirable but maybe unrealistic E resolution
KamLAND: 0.065 MeV0.5
Detector energy resolution, MeV0.5
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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
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?
Earth’s Total Heat Flow
• Conductive heat flow
measured from borehole temperature
gradient and conductivity
Data sources
What is the origin of the heat?
Total heat flow
Conventional view
441 TW
Challenged recently
311 TW - ?
Radiogenic heat and geo-neutrinos
40K-decay
Detectable
>1.8 MeV
modes
Th-decay chain
238U
(“Radium”)-decay chain
n
p + e- + e
2 more decay chains:
235U “Actinium” – no -decays with
sufficient energy
“Neptunium” – extinct by now
Urey Ratio and
Mantle Convection Models
radioactive heat production
Urey ratio =
heat loss
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Mantle convection models typically assume:
mantle Urey ratio: 0.4 to 1.0, generally ~0.7
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Geochemical models predict:
Urey ratio 0.4 to 0.5.
Discrepancies?
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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
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U and Th are thought to be absent from the core and
present in the mantle and crust.
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U and Th concentrations are the highest in the continental
crust.
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Core: Fe-Ni metal alloy
Crust and mantle: silicates
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
Continental detectors
dominated by
continental crust geoneutrinos
Oceanic detectors can
probe the U/Th
contents of the mantle
Reactor Flux irreducible background
Geoneutrino flux determinations
-continental (DUSEL, SNO+, LENA)
-oceanic (Hanohano)
Current status of geo-neutrino studies
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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
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Baseline on the order of 50 km; better variable
for different studies
Big number of events (large detector)
For Hierarchy and m213/23:
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Good to excellent energy resolution
sin2(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 
Production in reactors
and natural decays
Key: 2 flashes, close in space and time,
2nd of known energy, eliminate background
Detection
Evis=Eν-0.8 MeV
prompt
delayed
Evis=2.2 MeV
• Standard inverse β-decay coincidence
• Eν > 1.8 MeV
• Rate and precise spectrum; no direction
Reines & Cowan
Hanohano: engineering
studies
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Studied vessel design up to 100 kilotons,
based upon cost, stability, and
construction ease.
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Makai Ocean Engineering
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
Deployment Sketch
Descent/ascent 39 min
Addressing Technology Issues
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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
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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
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Better precision for sin2(212), sin2(213) – to 2%
possible with Hanohano
If sin2(213)  0: high precision measurement of
m213, m223, and even mass hierarchy possible with
the same detector; for sin2212 = 0.05, m213, 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