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KamLAND ResultsKamLAND Results
Junpei ShiraiJunpei Shiraifor the KamLAND Collaboration for the KamLAND Collaboration
Tohoku UniversityTohoku UniversityNOW2006, Conca Specchiulla, ItalyNOW2006, Conca Specchiulla, Italy
Sep.10-15, 2006Sep.10-15, 2006
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SUN…SUN…EarthEarth
ReactorReactor
KamLAND
KamLAND(Kamioka Liquid scintillator
Anit- Neutrino Detector)
Challenges real time detectChallenges real time detection of ion of Low energy neutrinos !Low energy neutrinos !
1: Reactor experiment2: Geo detection3: Solar detection
Properties of neutrinosProperties of neutrinos andandNeutrino-generation Neutrino-generation Mechanizms in nature.Mechanizms in nature.
etc.10MeV
K.Nakamaura et al
Supernova
Relic supernova
1MeV
Geo Reactor
Solar
Galactic Atmospheric
Expected neutrino spectra from various sources
KamLAND CollaborationKamLAND Collaboration
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A.SuzukiA.Suzuki
Tohoku University, Japan,Tohoku University, Japan,California Institute of Technology, USACalifornia Institute of Technology, USAUniversity Bordeaux 1, France,University Bordeaux 1, France,Drexel University, USA,Drexel University, USA,IHEP, China,IHEP, China,Kansas State University, USA,Kansas State University, USA,Triangle Universities Nuclear Lab., USA,Triangle Universities Nuclear Lab., USA,
University of Alabama, USA,University of Alabama, USA,University of Hawaii, USA,University of Hawaii, USA,University of New Mexico, USA,University of New Mexico, USA,University of Tennessee, USA,University of Tennessee, USA,Lawrence Berkeley National Lab., USA,Lawrence Berkeley National Lab., USA,Louisiana State University, USA,Louisiana State University, USA,Stanford University, USAStanford University, USA
~90 physicists from 14 Institutes
KamLAND Reacotor experimentKamLAND Reacotor experimentKamLAND Reacotor experimentKamLAND Reacotor experiment
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Challenging the Solar Neutrino Problem (SNP)
Challenging the Solar Neutrino Problem (SNP)Long History since late 1960's!
Cl, H2O, Ga experiments all showed significantly less flux than the SSM prediction.
Neutrino oscillation naturally explained the results, but several solutions existed in (m2-mixing angle) plane. SNO discovered active non-e component in the flux by using both CC (only e) and NC (total active ’s) reactions. This strongly suggests neutrino oscillation.The LMA (m2~105eV2) solution seems quite promising, but no single experiment uniquely determined the solution.
A decisive experiment is needed using man-made neutrinos.A decisive experiment is needed using man-made neutrinos.Reactor experiments have played a crucial role in this point !Reactor experiments have played a crucial role in this point !
[SNP]
Reactor: powerful tool for studying neutrino oscillationReactor: powerful tool for
studying neutrino oscillation
Pure and high intensity neutrino "beam" is provided.Pure and high intensity neutrino "beam" is provided.
n+235U→X+Y+2n
Fission products: neutron rich → - decays→[~6's]+[~200MeV]/fission
Typical power reactor (3GWth)→ 5.6×1020 /s, ~1/4 is detected by
ee
The energy is low:The energy is low: E 8.5MeV→<~
The flux and the spectrum of are well understood. The flux and the spectrum of are well understood. ee
[Power reactors] Isotopic components of the fuel elements(235U, 239Pu, 238U, 241Pu) are estimated by the initial ones and the thermal power. The flux and spectrum of each element is studied and the total flux uncertainty is ~2% !
A large L/E factor in sin2 is obtained
m2L 4E
to be sensitive to small m2.
e p→e+n
Long history since the first detection of neutrinos by F.Reines in 1950's.
Reactor experimentsReactor experiments
e
ee
Detector
Disappearance experiment
1-sin22sin2m2L 4E
No oscillation up to a distance No oscillation up to a distance L~ O(1)km (L~ O(1)km (mm22<O(10<O(10-3-3) eV) eV22).).
ee
e p→e+n
Neutrino flux has been well understood.
The technique using a large volume (~10tons) liquid scintillator has been established.
Before KamLAND,
Liquid scintillator
Cross section of has been understood very precisely (0.2%).
e p→e+n
N obs
./N n
o-os
cil
Reactor
(L: flight distance)
KamLAND reactor neutrino experiments
KamLAND reactor neutrino experiments
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Kamioka
53 Japanese power reactors.53 Japanese power reactors.26 are concentrated at 26 are concentrated at L=138-214km with 80GWth!L=138-214km with 80GWth!
<L>~180km<L>~180km
KamLAND1000ton LS
With ~100 times larger L/E With ~100 times larger L/E than before KamLAND is senthan before KamLAND is sensitive to sitive to mm2 2 ~10~10-5-5eVeV22 and c and can test the solar LMA soluan test the solar LMA solution!tion!
KamLAND DetectorKamLAND DetectorSite: Kamioka undergroundmine, Gifu prefect., 2700m.w.e.Cosmic muon rate: 0.34Hz
Calibrationdevice
Rn free air
Stainless steel tank (18m)
13m
LS(Normal dodecane(80%)+Pseudo-cumene(20%) +PPO(1.5g/l))
Balloon(135mt; EVOH/3Ny/EVOH)Buffer oil (Normal dodecane+ iso-paraffin: 2.5mt, LS-BO=-0.04%)
1325 17”PMTs+554 20”PMTs(34% of 4, 350p.e./MeV,t~1.9ns (17”PMT))
Pure water (3.2kton)20m 225 20”PMTs
Rock
Outer Detector
Central Detector
KamLAND areaKamLAND area
Control room
Rn-free gas system
Detector
Water purification systemWater purification system
2.2km
1km
To the mine entrance
Oil purification system
Mt.Ikenoyama
Time and space correlation, andTime and space correlation, andDelayed Delayed energy energy → → Significant reduction of backgorunds Significant reduction of backgorunds
detection in KamLANDdetection in KamLANDdetection in KamLANDdetection in KamLAND
ep
e+e
n
p
d
(0.51)
(0.51)
(2.2MeV)
[Prompt e+ signal]
[Delayed by neutron capture]
[E1.8MeV]Eprompt
=Te++ annihilation 's=E0.8MeV
~200s
Te+
+ p e+ + n
e
Results of reactor
PeriodExposure(ton ・ y)
|rp|,|rd|
(m)|rp-rd| (m)
Tp-d (s)Ed (MeV)
Ep (MeV)
Nno-osc.exp
Nobs
Nbkg
Mar.4- Oct.6, '02
162 < 5m1.6 m0.5-6601.8-2.6 > 2.6
86.8±5.6 54 1±1
Mar.9, '02- Jan.11,'04
766 5.5 2
0.5-1000Same
2.6-8.5365±23.7
258 17.8±7.3
1st 2nd
0.611±0.611±0.085±0.0410.085±0.041
0.658±0.658±0.044±0.0470.044±0.047
[99.95%CL] [99.998%CL]
Phys.Rev.Lett. 94, 081801 (2005)
2.6MeV
Disappearance !Disappearance !
Spectral DistortionSpectral DistortionNno-osc.exp
[Nobs-Nbkg]
Oscillatory behaviorOscillatory behavior
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Decay
Decoherence
Oscillation
L0/E distribution (180km)
Δ m2=
7.9+0.6-0.5 ×10-5eV2
tan2θ= 0.4+0.10-0.07
Solar+KamLANDOscillationOscillationparametersparametersare preciselyare preciselyDetermined !Determined !
10-5
10-4
m2
eV2
m2 (e
V)2
tan20.1 1 10
tan25
6
7
8
9
10
411
12×10-5
Prospects of KamLAND reactor expereiment
Prospects of KamLAND reactor expereiment
“4 system”
3% rate error 1% scale error 3kt-yr data taking
Keep data taking !Keep data taking !Reduce systematic error by a new calibration systemReduce systematic error by a new calibration systemin place of the vertical-axis calibration. in place of the vertical-axis calibration.
Detector (%)Fiducial vol. 4.7Energy threshold 2.3Efficiency of cuts 1.6Live time 0.06
Reactor power 2.1Fuel composition 1.0e spectra 2.5Cross section 0.2
Now ready !
Systematic error : 6.5%
KamALND: challenging GeoneutrinosKamALND: challenging Geoneutrinos
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Large heatflow from the EarthLarge heatflow from the Earth
~60mW/m244.2±1.0 TW (Pollack, '93),31±1 TW (Hofmeister, '05)(~10,000 power reactors)
The heat source has not been well understood.The heat source has not been well understood.Volcanoes, earthquakes,Plate tectonics,Plume tectonics,Magnetic field of the Earth
Dynamics of the Earth
Radiogenic heat has been considered to be very important!Radiogenic heat has been considered to be very important!Carbonacious chondrite :Chemical component of the earth [BSE (Bulk Silicate Earth) model]
238U(8TW), 232Th(8TW),40K(3TW)
19TW
Measured points>20,000
Geoneutrinos as a probe of Radiogenic Heat
Geoneutrinos as a probe of Radiogenic Heat
4040KK
.5 1 1.5 2 32.51.8MeV1.8MeV 3.27MeV3.27MeV
214Bi212Bi
KamLAND
€
e p→ e+n
238238UU
234Pa228Ac
208Tl
232232ThTh
238U→206Pb: 6 +51.7MeV232Th→208Pb: 4 +42.7MeV
40K→ 40Ca+e-+ +1.31MeVee
e
[89%]
Direct information of radiogenic heat ! (Eder('66), Marx('69))Direct information of radiogenic heat ! (Eder('66), Marx('69))
KamLAND: Geo- AnalysisData sample: Live-time 749.1±0.5 days (Mar.'02-Nov.'04)
Selection conditions (after the on cut)Low energy (<3.3MeV) Background (external , radio-impurity)
Fiducial vol (|rp|, |rd|) < 5m|rp-rd| < 1m
Tp-d 0.5s- 500sEprompt 0.9-2.6MeV
Ed
Efficiency (68.7±0.7)%
<5.5m< 2m
0.5s- 1000s
same
2.6-8.5MeV
(89.8±1.5)%
[2nd reactor][Geo
1.8-2.6MeV
Energy spectra in KamLAND
(α,n)
Th U
BG-totalEvents/0.17MeV
Data
Geo-νNature 436, 499 (2005)
Accidentals
Antineutrino Energy EAntineutrino Energy E(MeV)(MeV)
Reactor ν
U, Th prediction prediction of the Earth modof the Earth model (16TW)el (16TW)
Reactor
Observed: 152 eventsEstimated BG: 127±13 events 2525 +19+19
-18-18 eventsevents
(80.4±7.2)
(42±11)
(2.38±0.01)
Rate+Shape analysisRate+Shape analysisN
U+
NT
h(ev
enta
)
(NUNTh)/(NU+NTh)
NU+NTh (events)
2 90%CL
4.5 54.2
Th/U mass ratio=3.9
U+Th=21 U+Th=21 (U=3, Th=18)(U=3, Th=18) U+Th=28U+Th=28
Consistent with the rate anConsistent with the rate analysis (alysis (25 25 ) and the E) and the Earth model (arth model (1919) within) within 1 1σ.σ.
The Earth model (Th/U mass ratio=3.9) U+Th=19
The Earth model (Th/U mass ratio=3.9) U+Th=19
U/Th freeU/Th free
+19+19-18-18Radiogenic Power
< 60TW (99%CL)
(,n) Background(,n) Background
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222Rn
210Pb 210Bi 210Po
206Pb5.3MeV)Quenched, 21.1Bq/FV
13C→16O(*)+n[1%]
16O*→, e+e- (~6MeV)n+p→n+p n+12C→12C*(4.4)+n
Primary
ReactorGeo
n+p→d+Secondary
n+p→n+p
12C*16O*
Uncetainty: 26%Cross section 20%210Po rate 14%Proton quench 10%
4% (New data)
Measurement with n beam
Events <0.9MeV
(t1/2=22.3y)
Reduce uncertaity of (,n)
Hit the LS with mono-energetic neutrons to measure visible energy of the recoil proton in n+p→n+p.
Neutron detectors(En, n)
LS sample
OKTAVIAN @OSAKA Univ.
Measurement of the proton quenching factor in n+p→n+p.
Measure (,n) events in KamLAND below 0.9MeV; pure (,n) events to know 210Po decay rate. → Continued, Needs statistics.
New cross section data of 13C(,n)16O. Harissopulous et al. (2005), sys. uncertaity 20%→4%.
KamLAND KamLAND 77Be Solar NeutrinoBe Solar Neutrino
DetectionDetection
KamLAND KamLAND 77Be Solar NeutrinoBe Solar Neutrino
DetectionDetection
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Towards Towards 77Be solar Be solar Towards Towards 77Be solar Be solar
5MeV5MeV300KeV300KeV
Long lived 210Pb(T1/2=22.3y) and 85Kr(T1/2=10.8y) in the LS must be removed by factors ~105!
SuperKSNO
KamLAND
77Be Be : Second largest flux. : Second largest flux. Theoretical Uncertainty is large (10%).Theoretical Uncertainty is large (10%).No direct measurement so far.No direct measurement so far.
7Be(862KeV)
Detection by KamLAND
ee--→→ee--
Single ionization eventwith Evis<665KeV.
Purification of the 1000 ton LS
Purification of the 1000 ton LS
LS
Purification by Purification by Distillation Distillation ((210210Pb) &Pb) &NN22 purge ( purge (8585Kr)Kr)
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LS
Construction of theConstruction of thepurification systempurification systemis finished this month !is finished this month !
Test plant(Tohoku
University)
7Be
Next year !Next year !Next year !Next year !
Lead removal
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(~3×10-5 reduction)
Purification Method
Distillation tower
TanksN2-purge tower
1.5m3/hr
KamLANDarea
Reactor & Geo-after
purification
Reactor & Geo-after
purification
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No reactor caseNo reactor case
±35%±35%
Afterpurification
The same data taking periodwith enlarged fiducial volume.
±54%(now)±54%(now)
Total data±28%
<30TW(99%CL)Check theEarth model !
No (,n) & Reduced accidentals
Fiducial volume isenlarged !
Geo
Reactor
(,n) accidental
Fast neutrons
16O*
14C*
6.5m
(R/6.5m)3Fid. Volume
Prom
pt Ene
rgy (M
eV)
5.5m5m
Reactor neutrino
Towards pep/CNO detection
10-6 reduction of 210Pb, 85Kr assumed
After removal of After removal of 210210Pb and Pb and 8585Kr, Kr, 1111C which is generateC which is generated by muons makes a dominant BG in 1~2 MeV region fod by muons makes a dominant BG in 1~2 MeV region for pep/CNO r pep/CNO detection. detection.
11C→11B+e++=29.4m, Q=1.98MeV
pep
RR
tt
Remove 11C by 3-fold coincidence
~95% of 11C production is accompanied by neutrons
1212C+X→C+X→1111C+n+Y+…C+n+Y+…
X=,n,p,,e,
1) Muon2) Neutron (2.2MeV af
ter ~200s)3) 11C decay(=29.4m)
11C-n
+ signal
200cm
select L<50cm,#ndetected>0)
KamLAND 11C detection
Take 3-fold coincidence:
1.4 1.6 1.8 2.01.21.0
Visible energy (MeV)
Pep/CNO : prospects
CNOpep
7Be
3 years data3 years data
1111CC
Improve muon fitter and muon tracking device.
5% of 11C remains.
New electronics to detect neutrons after the large muon signal (design finished).
Issues:
Next slide
Electronics for 11C tagging Design finalized
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ickTi
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Main Circuit
AnalogueFront End Circuit
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High multiplicity events after the muon (spallation neutrons)with absolutely zero dead-timeand quick recovery
×12 /main board
8B solar
from Pena-Garay
To find upturn toward the low energy by the Matter effect.
232Th concentration in the LS is (5.2±0.8)×10-17 g/g from Bi→Po decay.
208Tl (→, 5MeV) in the LS dominates the signal.
232Th: 212Bi→212Po KamLAND
0.17Bq/m3
Mar-Sep,2002
If Th is removed by purification If Th is removed by purification to ~10to ~10-3-3, then we have a chance !, then we have a chance !
212Po
208Tl
212Bi
208Pb
(36%)
(64%)
KamLAND: SummaryKamLAND: SummaryKamLAND: SummaryKamLAND: Summary
First challenge of Geo-neutrino detection has been made by KamLAND. Further reduction of systematic uncertainty of (,n) background is underway.
Construction of a new purification system is finished this month and we start LS purification right away.
KamLAND has established e oscillation. Under the CPT invariance the SNP has been solved and oscillation parameters have been determined.
KamLAND enters the solar phase next year. High quality data of reactor and geo-neutrinos will also be obtained.
New "4 calibration system" has been ready for significantreduction of systematic errors to get improved measurement of oscillation parameters.
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