05.09.19suekane 05 erice school1 kamland f.suekane research center for neutrino science tohoku...
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05.09.19 suekane 05 Erice School 1
KamLAND
F.SuekaneResearch Center for Neutrino Science
Tohoku University
Erice School 2005.9.19
05.09.19 suekane 05 Erice School 2
KamLAND Collaboration
05.09.19 suekane 05 Erice School 3
Contents
* Introduction to KamLAND
* Physics with e
Reactor-e
Geo-e
Solar-e
* Future prospects 7Be Solar phase 4 calibration system New Reactor
* Summary
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e world e Flux at Kamioka
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
1E+2
1E+3
1E+4
1E+5
1E+6
1E+7
1E+8
1E+0 1E+1 1E+2 1E+3 1E+4 1E+5
Antineutrino Energy (MeV)
Flux (/cm
2 /s/MeV)
Atmospheric ν e
Geo-νe
Reactor ν e
Solar ν e
(0.01% transition)
ν e fromPast Super Novae
Main purpose of KamLAND
is to explore the e world with;
world largest & low-background
liquid-scintillator e detector.
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KamLAND Detector
Cosmicray veto
Balloon
S.S. tank
PMT
Liquid Scintillator
buffer oil
Electronics
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Oil Purification system
Rn free N2 Gas Generator
Corridor to detector
Water Purification systemMonitor Displays
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Key Detector Elements* Liquid Scintillator: Dodencane(80%)+PC(20%)+PPO(1.5g/L) (1150m3) Light output ~8,000photons/MeV att.>10m
* Balloon: 13m diam. 135m thick Nylon/EVOH multilayer film. Held by Kevlar mesh.
* PMT: 1325 17" aperture fast PMT (Newly developed) + 554 20" aperture (Kamiokande PMT) 34% photo-coverage
* Purification system: Water extraction + N2 bubbling U =>3.5x10-18g/g
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Event Display: Cosmic-Ray Event
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Event Display: Low Energy Event
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Single Background
208Tl decay ~2.5/day
238U/222Rn: 3.5x10-18g/g = 20Bq232Th: 5.2x10-17g/g =100Bq40K: <2.7x10-16g/g =<0.04Bq
Reactor analysis threshold
e threshold
(cf: sea water contains10-9g/g of U.)
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e detection
n+p→ d+γ 2.2MeV( )
ν e +p→ n+e+
2.2MeV~200É s
1~8MeV
t
Signal Property
e+ signal n signal
e+ +e−→ 2γ
Eν −0.8MeV( )
(ep -> e+n); an ideal reaction, because
• Only e contributes (no background from other neutrino species)• Low threshold Energy (1.8MeV)• Large cross section (~100e) • p is abundant in LS• Cross section precisely known (=0.2%)• e energy can be measured (E=Evisible+0.8MeV)• Delayed Coincidence -> powerful background rejection
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ep crossection and neutron lifetime
ν ep→ e+n
e+
W −
p n
GF 2 cosθCγ μ 1− CAγ 5( )
GF 2γ μ 1− γ 5( ) ν e
n→ pe−ν e
W −
pn
GF 2 cosθCγ μ 1− CAγ 5( )
GF 2γ μ 1− γ 5( )
e−
ν e
€
p→e+n
=2π 2
I ΔM , me( )
Eν Ee
τ n
= 9.6 ×10−44 1± 0.002( )Eν Eecm2
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Electron Antineutrino Event Rateat Kamioka
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
1E+2
1E+3
1E+4
1E+0 1E+1 1E+2
Antineutrino Energy (MeV)
Event rate (/year/kt//MeV)
Geo- e
Reactor e
e from Past Super Novae
Atmospheric e
KamLAND 1 /event yearsensitivity
Inverse beta decay threshold
Solar e(0.01%)
€
fν Eν( ) ×σν p→e+n
Eν( )
- KamLAND can see * Reactor Neutrino -> Neutrino Oscillation
* Geo Neutrino -> Heat Generation of Earth
* Solar e if 0.01% of e -> e
- But difficult to see * e from past SN * Atmospheric e
- If e is observed at E>9MeV, => Unknown e source
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A brief history of KamLAND
Detector Construction 1997~Start Data Taking 01/20021st reactor paper (deficit) 12/2002 (PRL 90:021802,2003)
Solar e search 10/2003 (PRL 92:071301,2004)
2nd reactor paper 06/2004 (PRL 94, 081801,2005)
(spectrum distortion)Geo neutrino paper 07/2005 (Nature 436:499-503,2005)
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Reactor NeutrinoElectron Antineutrino Event Rate
at Kamioka
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
1E+2
1E+3
1E+4
1E+0 1E+1 1E+2
Antineutrino Energy (MeV)
Event rate (/year/kt//MeV)
Geo- e
Reactor e
e from Past Super Novae
Atmospheric e
KamLAND 1 /event yearsensitivity
Inverse beta decay threshold
Solar e(0.01%)
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Reactor Neutrino
n U235
U236*
n n
Zr94140Cs
I140
Te140
Xe140
Rb94
Sr94
Y94
e-
e-
e-
e-
e-
e-
e
e
e
e
e
e ~6 /fission & ~200MeV/fission
⇓~6×1020ν e /s/reactor
Neutrino Spectra
E~ a few MeV
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ep cross section
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Distance to the reactors
68GWth
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If Neutrino Oscillation Exists
€
N Eν( ) = N0 Eν( ) 1−sin2 2θsin2 Δm2L4Eν
⎛
⎝ ⎜
⎞
⎠ ⎟
=> Deficit of neutrino events
=> Distortion of energy spectrum
Thanks to the very long baseline and low reactor neutrino energy,KamLAND is sensitive with verylow m2.
Δm2 =2πEν
L~
2π ×4MeV180km
~10−5eV2
LMA region is covered!!
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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
(Mar. 9, 2002 ~ Jan. 11, 2004)
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€
e + p → e+ Eν − 0.8MeV( ) + n
n + p → d +γ 2.2MeV( )
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Neutrino Event Spectrum
Probability of No Deficit =0.002%Probability of No Distortion=0.4%
258events
17.8events
365.2events expected
arXiv:hep-ex/0406035 v3
Background
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206Pb+210Po138.4 d
Back grounds
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Distortion Pattern
Oscillation back
€
Pν →ν =1−sin2 2θsin2 Δm2
4
⎛
⎝ ⎜
⎞
⎠ ⎟
LEν
⎛
⎝ ⎜
⎞
⎠ ⎟
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Reactor Power Variation
Consistent withEstimated BG
No Oscillation Case
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Oscillation Parameters
€
m2 = 7.9−0.5+0.6 ×10−5 eV 2 , tan2θ = 0.40−0.07
+0.10
KamLAND Only KamLAND+Solar
Solar LMA Solution
€
m2 = 7.9−0.5+0.6 ×10−5 eV 2 , tan2θ = 0.46KamLAND only:
KL+Solar:
(PRL 94, 081801,2005)
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Impact of the KamLAND Result
to the Future Neutrino Physics
sin21 and m212 turn out to be not so small.
(@ oscillation maximum; )
people
Leptonic CP violation l may be accessible in the Future Experiments. Because CP asymmetry ACP can be l
arge:(Not for the case of SMA or LOW solution)
€
ACP =P ν μ → ν e( ) − P ν μ → ν e( )P ν μ → ν e( ) + P ν μ → ν e( )
≈Δm12
2
Δm132
sin2θ12
sinθ13
sinδl > 0.14sinδl
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Geo NeutrinosElectron Antineutrino Event Rate
at Kamioka
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
1E+2
1E+3
1E+4
1E+0 1E+1 1E+2
Antineutrino Energy (MeV)
Event rate (/year/kt//MeV)
Geo- e
Reactor e
e from Past Super Novae
Atmospheric e
KamLAND 1 /event yearsensitivity
Inverse beta decay threshold
Solar e(0.01%)
Nature 436, 28 July 2005
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ep threshold
U series:Qheat=49.7MeV
Th series:Qheat=40.4MeV
e from U/Th/K decay
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U/Th abundance in the earth
Observations: •Chondristic Metrites (~average earth composition) contains a few 10ppb of U and Th. => ~4x1017kg of U+Th => The heat generation is ~15TW(40% of total heat dissipation)
•Earth crust contains a few ppm of U and ThMost of U,Th is concentrated in continental crust.distribution is roughly known.
Radiogenic Heat Source of EarthPhD N.R.Tolich
PhD S.Enomoto
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Why Geo-Neutrinos?
Observation of Geo neutrino Abundance and Localization of U and Th Thermal Structure and History of the earth - Is the earth cooling or equilibrium state? - What is the future of the earth? - What is the residual heat of the earth formation? - What drives the geo magnetic field?
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expected e energy spectrum
and event selection
€
N Eν( ) = N0 Eν( ) 1− sin2 2θsin2 Δm2L4Eν
⎛
⎝ ⎜
⎞
⎠ ⎟
€
sin2 2θ = 0.82 ± 0.07
Δm2 = 7.9−0.5+0.6 ×10−5 eV 2
⎧ ⎨ ⎩
Data sample: live time 749.1dEvent selection: Fiducial volume: R<5m T: 0.5s-500s R<1m E: 1.7-3.4 MeV (Epromt: 0.9-2.6MeV) Edelayed: 1.8-2.6MeV
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Reactor 13C(,n)16O
238U232Th
Accidental
Expected total backgrounds
Expected total
Observed e candidates 152 eventsExpected total backgrounds 127±13 events
25+19-18
events
U+Th geo-Candidates: Rate only
2nd reactor results
Geo-
BSE model:19 events
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Rate + Shape analysisC.L. contours for detected U and Th geo-s.
NU+
NT
h
(NUNTh)/(NU+NTh)
Th/U massRatio=3.9
NU+NThPrediction from theBSE model(19 events) Best fit: 3 U and
18 Th Geo-'s.
2 90%CL
4.5 54.2
NNUU+N+NThTh::
Consistent with predictionConsistent with prediction of geophysical model. of geophysical model. Geo-Geo- detection @95%! detection @95%!
Th/U Mass ratio=3.9
U+T < 60TW (99%CL) U+T < 60TW (99%CL) Constraint by direct method!Constraint by direct method!
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e with E>9MeV
There is no known e source with flux high enough to be detected by KamLAND. If any e events are observed, it is unknown e source.
Electron Antineutrino Event Rateat Kamioka
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
1E+2
1E+3
1E+4
1E+0 1E+1 1E+2
Antineutrino Energy (MeV)
Event rate (/year/kt//MeV)
Geo- e
Reactor e
e from Past Super Novae
Atmospheric e
KamLAND 1 /event yearsensitivity
Inverse beta decay threshold
Solar e(0.01%)
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Solar e
€
e = sinθν 2 + cosθν 1
ν 2decay ⏐ → ⏐ ⏐ ν 1 + X
ν 1 = cosθν e +sinθν μ
€
e
Spin−flavor precession with solar
r B ⏐ → ⏐ ⏐ ⏐ ⏐ ⏐ ν μ
flavor Oscillation ⏐ → ⏐ ⏐ ⏐ ⏐ ν e
€
Pν e →ν e∝ μ ν B
No reactor region
Two possibilities( has to be Majorana)
(1)
(2)
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Event selection
0.28kt yearE=8.3MeV~14.8MeV => 0 event (1.1 +/- 0.4 BKG)
f<3.7x102/cm2/s (90%CL) <2.8x10-4 of 8B e
Reacotr
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e with E>15MeVElectron Antineutrino Event Rate
at Kamioka
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
1E+2
1E+3
1E+4
1E+0 1E+1 1E+2
Antineutrino Energy (MeV)
Event rate (/year/kt//MeV)
Geo- e
Reactor e
e from Past Super Novae
Atmospheric e
KamLAND 1 /event yearsensitivity
Inverse beta decay threshold
Solar e(0.01%)
* Relic SN e
* Atmospheric e
However, too few to be detected by KamLAND
=>If KamLAND observes any e, it is unknown e source.
....... Analysis in progress.....
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Flux Suppression
for LMA
pp&7Be- ~60% suppression
Y.Suzuki
But is it really so?
Future of KamLAND Solar 7Be detection
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Back grounds
Total
210Po 210Bi85Kr
7Be11C
14C4 m radius fiducial1.2 m cylindrical cut
Required Reductions: 210Pb: 10-4~10-5
85Kr: ~10-6
e scattering has to be used.Decayed coincidence can not be used
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LS Purification Distillation System
Test 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 in small system & Purification system construction is starting.
residual Pb might be organic lead(disintegrate at ~ 200℃)
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4 calibration system
vertical calibration + uniformity of events3dimensional calibration Improve fiducial volume error Improve sin2212 accuracy
Installation 2005 Fall
to reduce this error
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New Reactor Shika-II
L=88km (~ Oscillation Maximum)Pth=3.926GW (~15% contribution)
Increase of # of events will besmall due to oscillation=> confirmation of the measurement
http://www.rikuden.co.jp/outline2/index.html
Now20062005
test operation schedule
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Summary•Reactor Neutrino Seen and m2=7.9x10-5, tan2=0.46 with KamLAND only.•Geo-neutrino Seen and consistent with earth models.
•Solar e Not seen. -> transition probability <2.8x10-4
•Preparation for solar 7Be neutrino detection in progress
•new 4 calibration system being installed.
•new reactor at ~oscillation maximum started to operation.