Download - Results and Future of the KamLAND Experiment
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Results and Futureof the
KamLAND Experiment
Sanshiro Enomoto (Tohoku Univ.)for the KamLAND Collaboration
WIN05 @ Delphi, Greece, 6-11 June 2005
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The KamLAND Experiment
80% of total contribution comes from 130~220km distance
1000ton LS1879 PMT's
LMAParameters
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The KamLAND Detector
20m
1000m
1000ton
1325 17-inch 554 20-inch
1.75m thickness
225 20-inch
13m diameter
13m LS:80%: dodecane20%: pseudocumene1.5g/l: PPO
~ 8000 photons/MeVλ~ 10m
MO:50%: dodecane50%: isoparafin
ρLS/ρMO = 1.0004photo-coverage: 34%~ 500 p.e. / MeV
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Detection Method
nepe MeV8.1threshold E
(2.2MeV) dpn
Analysis Range(E > 2.6 MeV)
MeV2.2
MeV78.0
delayed
prompt
E
EEeτ~210 μsec
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LS Purification and Radioactive Impurity
beforeU: ~10-10 g/g, Th: <10-12 g/g, K: 7×10-11 g/g
afterU: 3.5×10-18 g/g, Th: 5.2×10-17 g/g, K: 2.7×10-16 g/g
measurable only by KamLAND itself !
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Detector Calibration
Radio-Active SourceDeployment
Muon SpallationProducts
Vertex Resolution (MeV) Ecm/6.20
Energy Resolution
E(MeV)%/ 6.2
Fiducial Volume Error: 4.7%
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Detector Activity (Singles Spectrum)
Major Background Sources: LS impurity (210Pb, 85Kr, 39Ar) extrinsic gamma (40K, 208Tl) muon spallation (10C, 11C, 12B, ...)
Normal Trigger Range
Low Energy Region
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Event Selection
Delayed Coincidence: 0.5 < ΔT < 1000μsec ΔR < 200 cm 1.8 < Edelayed < 2.6 MeV
Fiducial Volume: Rprompt < 550 cm Rdelayed < 550 cm
Spallation Cuts: ΔTμ > 2 msec ΔTμ > 2 sec (showering muons) or ΔL > 300 cm (non-showering)
Energy Window: 2.6 < Eprompt < 8.5 MeV
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Backgrounds Summary
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Accidental Coincidence Background
⇒ 2.69 ± 0.02 events
off-time coincidence spectrum
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(α, n) Background
13C (α,n) 16O 13C (α,n) 16O*
14N (α,n) 17F15N (α,n) 18F17O (α,n) 20Ne18O (α,n) 21Ne
α
n
206Pb210Bi 210Po
210Pb
5.013 d
22.3 y
stable138.4 d
n + p → n + p
n + 12C →n + 12C*
12C + γ(4.4MeV)
16O*(6.13) → 16O + γ 16O*(6.05) → 16O + e+ + e -
232Rn3.8 d
(5.3 MeV)
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(α, n) Background
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Analysis
• Observed/Expected: R = 0.658 ±0.044(stat) ± 0.042(syst)⇒ neutrino disappearance at 99.998% C.L.
• Hypothesis test of scaled no-oscillation: χ2/ndf = 37.3/19⇒ spectral distortion at > 99.6% C.L.
• Rate + Shape: 99.999995% C.L.
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L/E Analysisχ2/ndf GOF
24.2/17 11.1%
35.8/17 0.7%
32.2/17 1.8%
spectrum shape test
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Oscillation Analysis KamLAND + Solarassuming CPT invariance
KamLAND best-fit (rate + shape)
10.007.0
2256.05.0
2 40.0tan,eV 109.7
m
46.0tan,eV 109.7 2252 m
KamLAND + Solar
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Correlation with Reactor Power
constrained to expected BG
4/4.22
at present statistics is not enough to state something
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Future of the KamLAND Experiment
Geo-Neutrino Detection(~ few weeks)
Improvements in Reactor Analysis(~ few months)
Solar Neutrino Detection(~ few years)
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Geo-Neutrino Detection at KamLAND
[MeV]1.31νeCaK
[MeV]42.7ν4e4He6PbTh
[MeV]51.7ν6e 6 He8PbU
e4040
e4208232
e-4206238
Radiogenic Heat ~ 20 TWObserved Surface Heat Flow: ~ 40TW
⇒ provides important constraints in Earth's energetics
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Geo-Neutrino Detection at KamLAND
[MeV]1.31νeCaK
[MeV]42.7ν4e4He6PbTh
[MeV]51.7ν6e 6 He8PbU
e4040
e4208232
e-4206238
Radiogenic Heat ~ 20 TWObserved Surface Heat Flow: ~ 40TW
⇒ provides important constraints in Earth's energetics⇒ provides unique knowledge in composition of Earth's interior
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Geo-Neutrino Detection At KamLAND
Expected Flux:• U-Series: 2.3x106 [1/cm2/sec] 30.1 [events/1032-protons/year]•Th-Series: 2.0x106 [1/cm2/sec] 6.7 [events/1032-protons/year]
Expected Events:(5 m fiducial, 515 day exposure)
• U-Series: 10.3•Th-Series: 2.7
•Reactor BG: 58•(α,n) BG: 30
data will be publishedin few weeks !
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Geo-Neutrino Detection and Extended Analysis Window
Analysis of low-energy region also benefits reactor analysis
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Further Improvements of Systematic Errors
results are mostly obtained from shape information, due to large systematic errors on rate
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Towards Solar Neutrino Detection
Total
210Po 210Bi
85Kr
7Be11C
14C4 m radius fiducial1.2 m cylindrical cut
Required Improvements: 210Pb: 10-4~10-5
85Kr, 39Ar: ~10-6
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LS Purification Distillation SystemTest Bench
• N2 gas purge (N2/LS = 25)Rn: ~1/10Kr: ~1/100
• Fractional Distillation (164 ℃, 300 hPa)
Pb: 3×10-5
Rn: 1×10-5
Kr: < 2×10-6
Required performance is almost achieved
residual Pb might be organic lead(disintegrate at ~ 200℃)
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Extrinsic Gammas Screening
7Be ν: ~1μHz 40K: < 3.4μHz 208Tl: < 5.6μHz
Current KamLAND Rate
MC of extrinsic gammas (40K, 208Tl)
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Solar Neutrino Prospects
11C
11C can be reduced with neutron tagging(pep and CNO neutrinos extractable???)
7Be neutrinos will be seenbetween 14C and 11C background
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Summary
• Rate+Shape analysis excluded no-oscillation at 99.999995%.
• Spectrum distortion (L/E) shows oscillatory behavior.• Oscillation parameters are precisely measured:
• Geo-Neutrino detection result will be published very soon.• Full-volume calibration will improve measurement.• Purification goal for 7Be neutrino measurement is
almost achieved.
2sin 2
10.007.0
2256.05.0
2 40.0tan,eV 109.7
m
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Energy Scale Determination
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Fiducial Volume CalibrationWith Muon Spallation (12B)
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Systematic Errors Summary
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Geo-Neutrino Flux and Earth Models
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Geo-Neutrino Flux Uncertainties
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Event Display: Low Energy Event
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Event Display: Muon Event