Current Status and Future Prospects of KamLAND
The 6th KEK Topical Conference Feb. 7, 2007
Itaru Shimizu (Tohoku Univ.)
観測エネルギー (MeV)1.0 2.6 8.50.4 太陽ニュートリノ 地球ニュートリノ 原子炉ニュートリノ 超新星ニュートリノ
e-
e-νx
νxsolar neutrino
n
pν̄e
e+
γ
γ
γ
anti-neutrino detection by inverse beta-decay
prompt
delayed
mean capture time ~ 200 µsec on proton
reactor neutrinogeo neutrino
neutrino detection by electron scattering
solar neutrino geo neutrino reactor neutrino supernova neutrino
observed energy (MeV)Physics Target in KamLAND
13 m
18 m
1,000 ton Liquid Scintillator
Water Cherenkov Outer Detector
Kamioka Liquid Scintillator Anti-Neutrino DetectorKamLAND
Pseudocumene (20%)PPO (1.5 g/l)Dodecane (80%)
1,325 17 inch + 554 20 inch PMTs
commissioned in February, 2003photocathode coverage : 22% 34%
Reactor Neutrino
νatm νsol
Solar Neutrino Problem
> 100 km baseline is necessary to explore the LMA solution
LMA
Other SolutionsRSFPFCNC
etc
SMA
LOW
VAC
LMA
川内
玄海 伊方
島根高浜 美浜
大飯
敦賀
志賀
柏崎刈羽
東海第二
福島第一福島第二
女川
泊
距離(km)0 100 200 300 400 500 600 700 800 900 1000
0
1000
2000
3000
4000
5000
6000
70009
x10)2
fiss
ion
/cm
12
Fis
sio
n n
um
be
r fl
ux
(10
0
2
4
6 U235
Pu239
U238
Pu241
ふげん
浜岡
180km
カムランド
Good condition to confirm solar neutrino oscillation
175 ± 35 km ~ 20%
ΔL (distance spread from reactors)
ΔE (energy resolution)
17 inch PMTs
17 inch + 20 inch
7.3% / E(MeV)
6.2% / E(MeV)
P (νe → νe) = 1− sin2 2θ sin2(1.27∆m2[eV2]l[m]
E[MeV])
2 flavor neutrino oscillation
most sensitive region
∆m2 = (1/1.27) · (E[MeV]/L[m]) · (π/2)
∼ 3× 10−5eV2
LMA solution
Reactor Neutrino Observation
KamLAND
distance (km)
• 0.5 < ΔT < 1000 µs• ΔR < 2 m• 1.8 MeV < Edelayed < 2.6 MeV• 2.6 MeV < Eprompt < 8.5 MeV
primary cuts fiducial cut + µ spallation cut• Rprompt, Rdelayed < 5.5 m• ΔTµ > 2 s after showing µ• ΔTµ > 2 s or ΔL > 3 m after non-showering µ (ΔQ < 106 p.e.)
efficiency 89.8% deadtime 9.7%
Neutrino Event Selection
20 30 40 50 60 70 800
0.2
0.4
0.6
0.8
1
1.2
1.4
(km/MeV)e!
/E0LRa
tio
2.6 MeV promptanalysis threshold
KamLAND databest-fit oscillationbest-fit decaybest-fit decoherence
766 ton-year data-set
Distortion : 99.6% C.L.
Evidence of Disappearance and Distortion
Disappearance : 99.998% C.L.
Rate Nobs / Nexpected (no oscillation) = 0.658 ± 0.044(stat) ± 0.042(syst)
Shapeχ2 / ndf = 37.3 / 19 (scaled no oscillation)
Rate + Shape (combined) 99.999995% C.L.
Precise Measurement of Oscillation Paramter
0.2 0.3 0.4 0.5 0.6 0.7 0.85
6
7
8
9
10
11
12-510!
!2tan
)2 (e
V2
m"
KamLAND + Solar95% C.L.99% C.L.99.73% C.L.global best fit
Other SolutionsRSFPFCNC
etc
SMA
LOW
VAC
LMA
∆m2 = 7.9+0.6−0.5 × 10−5 eV2
tan2 θ = 0.40+0.10−0.07
solar + KamLAND result
Geo Neutrino
U series Th series
Anti-neutrinos are generated by beta-decay,and it produces radiogenic heat
Geologically Produced Anti-neutrinos
radiogenic heat generation
planet dynamics and formation mechanisms
ν̄e
Geo neutrino detection directly teststhe radiogenic heat generation
44TW or 31 TWheat flow from surface understanding heat
BSE (bulk silicate Earth) model
analyses of meteoriteothers
(primordial heat,latent heat)
U ~ 8 TWTh ~ 8 TWK ~ 3 TW
total ~ 19 TW
Earth Energetics
Reference Earth Model
mantle core
UCC U : 2.8 ppm / Th : 10.7 ppmMCC U : 1.6 ppm / Th : 6.1 ppmLCC U : 0.2 ppm / Th : 1.2 ppm
oceanic crust U : 0.10 ppm / Th : 0.22 ppm
{{
U : 0.012 ppm / Th : 0.048 ppm U : 0 ppm / Th : 0 ppm
Mantle = Meteorite (BSE model) − Crust
Rudnick et al. (1995)
no U/Th in core
continental crust
Th/U ~ 3.9radiogenic heat ~ 16 TW
chondrite meteorite
Anti-neutrino energy, E! (MeV)
Even
ts /
0.17
MeV
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.40
5
10
15
20
25
30
Anti-neutrino energy, E! (MeV)
Even
ts /
0.17
MeV
2 4 6 80
5
10
15
20
Anti-neutrino energy, E! (MeV)
Even
ts /
0.17
MeV
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.40
5
10
15
20
25
30
Anti-neutrino energy, E! (MeV)
Even
ts /
0.17
MeV
2 4 6 80
5
10
15
20
UTh(α, n)
reactor
accidental
B.G. total
16 TW U/Th
radiogenic heat production rate [TW]
/sec]
2 f
lux (
U +
Th
) [1
/cm
e!
0 10 20 30 40 50 60 70 800
5
10
15
20610!
BSE Fully-Radiogenic
99% C.L. upper limit
68.3% C.L.
crustmantle
Observation and Reference Earth Model
sediment
B.G. expected 127 ± 13
Observed events 152
Systematic error 5.0%
25 event excess !
Result
3.8 times Reference Earth Model is excluded at 99% C.L.The data is consistent with the expectation (BSE model).
Further Improvement
(km/MeV)e!
/E0L
20 30 40 50 60 70 80 90 100
Rati
o
0
0.5
1
1.5
2
2.5
3
georeactor
R 5.5 m 515.1 day
R 5.0 m 749.1 day
1. 4pi calibration
2. (α, n) background estimation
3. combined analysis
first off-axis deployment
geo neutrinocontribution
Systematic error is dominated by the ‘fiducial volume uncertainty’full volume calibration
proton quenching measurement, Po/13C source calibrationIn low energy region, (α, n) background has large spectrum uncertainty
Low energy information is useful to improve the oscillation sensitivityall volume analysis using Eprompt, Edelayed, ΔR, ΔT, R, ΔTµ, ΔQ, ΔL
Future ProspectsKamLAND II
(Solar Neutrino Phase)
neutrino energy [MeV]
-110 1 10
])-1
sec
-2]
(fo
r lin
es, [c
m-1
MeV
-1 s
ec
-2fl
ux [
cm
210
310
410
510
610
710
810
910
1010
1110
1210!solar
U!geo
Th!geo
K!geo
!reactor
Future Solar Neutrino Measurement
pep7Be
pp
8B
low energy solar neutrino observation
Super-KamiokandeSNO
CNO
BorexinoKamLAND IISNO+LENA
XMassGENIUSCLEANHERON
LENS (115In)MOON (100Mo)SIREN (160Gd)
well understood
νee− → νee
−νen→ e−p
~ 0.01%
~ 9%~ 91%
development stage ...
low energy
high energy
KamLAND II (Solar Neutrino Phase)KamLAND singles spectra
7Be ν
B.G. reduction requirement ~ 1 µBq / m3
7Be ν observation
Energy Spectra after Purificationassuming 10-6 reduction of 210Pb, 85Kr and 40K
7Be ν
pep / CNO ν
7Be ν 79.9 event / day
Fiducial 4m
pep ν 3.8 event / dayCNO ν 16.3 event / day
expected event rate (no oscillation) 0.3 < E < 0.8 MeV
Purification of Liquid Scintillatordistillation methodseparation of substances based on boiling point differences
~ milli-liter system
~ liter system
real system
~ 1.5 kilo-liter / hour
Time [hour]0 20 40 60 80 100 120 140
cou
nts
/s
-410
-310
-210
-110
1
10
210
310
410 1st trial
/ndf = 3.47/8 A = 0.0002(0.0001) C = 0.0050(0.0009)2
no distillation sample
/ndf = 1038.19/8 A = 0.0012(0.0002) C = 7.0451(0.0536)2
3rd trial
/ndf = 19.38/10 A = 0.0003(0.0000) C = 0.0018(0.0005)2
5th trial5th trial
/ndf = 4.44/4 A = 0.0004(0.0001) C = 0.0002(0.0004)/ndf = 4.44/4 A = 0.0004(0.0001) C = 0.0002(0.0004)22
Reduction Efficiency by Distillation
radioactivenuclei reduction goal
40K 3.8 × 10-2
(PPO, 40K) 10-1 ~ 10-2
85Kr < 1.3 × 10-5
(Dodecane, Kr) 10-5 ~ 10-6
210Pb < 7.6 × 10-5
(Dodecane, 212Pb) 10-4 ~ 10-5
222Rn 6.0 × 10-4
(Dodecane, 222Rn) ~ 10-3
distillation in ~ liter-system
f(t) = Cexp(−t/τ) + A
τ ( 212Pb) = 15.4 hour
Pb reduction
Kr reduction
almost succeeded in the reduction goal
Radon Detector : miniLAND222Rn sensitivity ~ 1 mBq / m3
miniLAND350 liter LS144 liter NaI Water
total 16 cells
5 inch PMTs
acrylic box light guidereflective board
2 m3 copper box20 ton lead shield(thickness 15 cm)
4 boxes
Muon Spallation Background7Be ν
pep / CNO ν
Fiducial 4m
Life time Q value Hagner et al.(ev/d/kton)
10C 27.8 sec 3.65 MeV (β+) 139
11C 29.4 min 1.98 MeV (β+) 1039
7Be 76.9 day 0.478 MeV (EC) 231
serious B.G. for pep / CNO ν
11C Rejection by Neutron Events
(Galbiati et al., hep-ph/0411002)
12C + X→ 11C + n + Y + · · ·X = γ, n, p, π−,π+, e, µ
n production rate ~ 95%
11C rejection by triple coincidence
(2) neutron (mean capture time ~ 210 µsec)
nuclear spallation reaction by cosmic-ray muons
ΔR11C
neutron
µ
(3) 11C (lifetime = 29.4 min)
(1) cosmic-ray muon
point-like rejection (not track-like)using neutron vertex information
Energy Spectra after 11C Rejection
visible energy [MeV]
0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5
ev
en
ts/0
.02
Me
V
0
100
200
300
400
500
600
700
11C
7Be
pepCNO
3 year livetime
pep + CNO flux error ~ 6% (statistical error)
268 m3 fiducial volume
11C rejection simulation
95% of 11C is rejected by neutron tagging prototype
new dead time free electronics
Summary• Reactor neutrino experiment contributed
to solutions in solar neutrino problem.
• We demonstrated that geo-neutrino observation is possible.
• We will observe 7Be, pep and CNO solar neutrino in KamLAND II.
- oscillatory shape of reactor anti-neutrinos- precise measurement of oscillation parameter
first step of “Neutrino geophysics” frontier