International Workshop : Neutrino Research and Thermal Evolution of the Earth

KamLAND

Hiroko Watanabe
Research Center for Neutrino Science (Tohoku Univ.)
for the KamLAND Collaboration
Tohoku University, Sendai, October 25-27, 2016

Contents

1. KamLAND
2. Geo-neutrino Measurements
3. Analysis Results
4. Summary

Contents

1. KamLAND
2. Geo-neutrino Measurements
3. Analysis Results
4. Summary‣KamLAND Collaboration
The Astrophysical Journal, 818:91 (8pp), 2016 February 10

doi:10.3847/0004-637X/818/1/91© 2016. The American Astronomical Society. All rights reserved.

KamLAND SENSITIVITY TO NEUTRINOS FROM PRE-SUPERNOVA STARS
K. Asakura1, A. Gando1, Y. Gando1, T. Hachiya1, S. Hayashida1, H. Ikeda1, K. Inoue1,2, K. Ishidoshiro1, T. Ishikawa1,
S. Ishio1, M. Koga1,2, S. Matsuda1, T. Mitsui1, D. Motoki1, K. Nakamura1,2, S. Obara1, T. Oura1, I. Shimizu1,
Y. Shirahata1, J. Shirai1, A. Suzuki1, H. Tachibana1, K. Tamae1, K. Ueshima1, H. Watanabe1, B. D. Xu1,18, A. Kozlov2,
Y. Takemoto2, S. Yoshida3, K. Fushimi4, A. Piepke2,5, T. I. Banks6,7, B. E. Berger2,7, B. K. Fujikawa2,7, T. O’Donnell6,7,
J. G. Learned8, J. Maricic8, S. Matsuno8, M. Sakai8, L. A. Winslow9, Y. Efremenko2,10,11, H. J. Karwowski12,13,
D. M. Markoff12,14, W. Tornow2,12,15, J. A. Detwiler16, S. Enomoto2,16, and M. P. Decowski2,17
The KamLAND Collaboration
1

2

Research Center for Neutrino Science, Tohoku University, Sendai 980-8578, Japan
Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study,
The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
3
Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
4
Faculty of Integrated Arts and Science, University of Tokushima, Tokushima, 770-8502, Japan
5
Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487, USA
6
Physics Department, University of California, Berkeley, California 94720, USA
7
Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
8
Department of Physics and Astronomy, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA
9
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
10
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
11
National Research Nuclear University, Moscow, Russia
12
Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA
13
The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
14
North Carolina Central University, Durham, North Carolina 27701, USA
15
Physics Departments at Duke University, Durham, North Carolina 27705, USA
16
Center for Experimental Nuclear Physics and Astrophysics, University of Washington, Seattle, Washington 98195, USA
17
Nikhef and the University of Amsterdam, Science Park, Amsterdam, The Netherlands
Received 2015 June 3; accepted 2015 December 15; published 2016 February 10

ABSTRACTIn the late stages of nuclear burning for massive stars (M>8Me), the production of neutrino–antineutrino pairs
through various processes becomes the dominant stellar cooling mechanism. As the star evolves, the energy ofthese neutrinos increases and in the days preceding the supernova a signiﬁcant fraction of emitted electron antineutrinos exceeds the energy threshold for inverse beta decay on free hydrogen. This is the golden channel for
liquid scintillator detectors because the coincidence signature allows for signiﬁcant reductions in backgroundsignals. We ﬁnd that the kiloton-scale liquid scintillator detector KamLAND can detect these pre-supernova
neutrinos from a star with a mass of 25Me at a distance less than 690 pc with 3σ signiﬁcance before thesupernova. This limit is dependent on the neutrino mass ordering and background levels. KamLAND takes data
continuously and can provide a supernova alert to the community.
Key words: neutrinos – supernovae: general
1. INTRODUCTION
The ﬁrst extrasolar neutrinos were detected from SN 1987A
by the Kamiokande-II(Hirata et al. 1987, 1988), IMB(Bionta
et al. 1987), and Baksan(Alekseev et al. 1987) experiments.
This data set has provided many insights into the properties ofSep. 2016 @Amsterdam

cooling these massive (M > 8 M:) stars is the loss of energy
due to n n¯ pairs created by thermal processes. Fromapplication of the discussion in Itoh et al. (1996) to Woosley &Heger (2015), the dominant process in most M > 10 M: stars
is the pair process, e+enn¯ . For other stars with smaller
masses, the plasmon decay becomes more important, g
nn .

1/20
* Institutions :4 from Japan
12 from US
1 from Europe* ~50 collaborators‣KamLAND Site and Detector

2/20

KamLAND
Kamioka Liquid Scintillator
Anti-Neutrino Detector(operated since 2002)

Kamioka Mine: reactor

Kashiwazaki

Shika

159km

neutrino cosmic ray

φ13m balloon

88km
Wakasa146~192km

Hamaoka

1000m
depth

180km 200km

1,000t Liquid Scintillator- extremely low impurity(238U:3.5×10-18g/g, 232Th:5.2×10-17g/g)- worldʼs largest LS detector!

φ18m stainless tank
Water Cherenkov Outer Detector

1,879 Photomultiplier Tubes * Photo coverage 34%‣KamLAND

3/20

KamLAND‣Detector Featureslarge volume & low backgrounds

2000~‣Physics
0.4

observed energy [MeV]

1.0

electron scattering

ν + e− → ν + e −6.5m
1,000 tLiquid Scintillator

2.6
inverse beta-decay

8.5
ν̄e + p → e+ + n

reactor neutrinos
solar neutrinos
PRL 100, 221803 (2008)
PRC 84, 035804 (2011) geo neutrinos
PRD 83, 052002 (2011)
PRC 92, 055808 (2015)
Nature Vol. 436 (2005)
supernova neutrinos, etc.
Nature Geoscience 4, 647-651 (2011)
PRD 88, 033001 (2013)

PRL 92, 071301 (2004)
Astrophys. J. 745, 193 (2011)
Astrophys. J. 818, 91 (2016)

Different neutrino physics
in a wide energy range‣KamLAND-Zen
KamLAND-Zen
2011~

Zero Neutrino
double beta decay search

4/20‣Detector Features
136Xe loaded LS was installed in KamLAND(344 kg 90% enriched 136Xe installed so far)‣Physics

6.5m
1.54m
Xe loaded LS ina mini-balloon

neutrino-less double beta decay
World best limit on neutrino effective mass

m

< (61

165) meV PRL 117, 082503 (2016)

Continue to use LS volume outside of miniballoon to measure anti-neutrino signals

‣Anti-neutrino StudiesPνe
ΔT=200µsece+γ(0.511MeV)e-promptγ(0.511MeV)

10

Events/10keV

inverse-beta decay

5/20
Simulation

9

Reactor ¯e87

no-oscillation

6noscillation

5

thermal diffusion

delayed

n

4

d

3

Geo ¯e2P1γ(2.2MeV)

0
0

1

2

3

4

NATURE GEOSCIENCE DOI: 10.1038/NGEO1205

5

6

7

8

9

Ep [MeV]

60

6
40
4
20

2
0

MantleKamioka Gran Sasso

flux and models. a, Measured

0

1

9

- Signature of neutrino
contribution from 238 U and 2320.8Th is estimated to be 19.9+9.2
9.1 TW- Directmeasurement
by KamLAND
and Borexino data, excluding the fully radiogenic
oscillationof modelradiogenic
heatCL. If we 0.6use the more recently determinedat the 96.6%- Precise measurement
heat-loss
rate
of
46
±
3
TW
(ref.
26)
the
fully
radiogenic
exclusion
0.4
contributionof oscillation parameters
increases to 98.0% CL, slightly enhanced owing to the larger mean
0.2
value of the heat flow as comparedref. 7, despitelarger3-iwithbest-fit oscillation
Data - BG - Geoitsierror. We conclude that these uncertainties
havelittleimpact
on
0
20
30
40
50
60
70
80
90
100
the results at this stage.
L /E (km/MeV)
It is expected that geoneutrino detectors operated at different
locations will significantly improve our knowledge of radiogenic
Survival Probability

νe flux (× 106 cm¬2 s¬1)

8 KamLAND Borexino

Radiogenic heat production
from 238U and 232Th (TW)

Geoneutrinos
Property
Study
contributions from the error in the Neutrinomass distribution andthe: Neutrino Application
fractional uncertainty in the Th:U ratio . The radiogenic heat

b

10

e

0

ie

Contents

1. KamLAND
2. Geo-neutrino Measurements
3. Analysis Results
4. Summary‣Geo-neutrinos

6/20
地球内部に含まれる放射性物質も、ベータ崩壊

Electron-antineutrino from natural radioactive decay
して反電子ニュートリノを放出する。
β-decay
Geo-neutrinos
62¯e 4.1 10 /cm /sec 238
238
206
U!

anti-neutrino
detector

232
232
Th !208 Pb + 6+ 4e + 4¯⇥e + 42.7 MeV
Th40
K !40 Ca + e + ¯e + 1.311 MeV (89.28%)
Energy threshold, 1.8 MeV

Thウラン、トリウム、カリウムなどは崩壊によってエネルギーを生成し10
U series
Th series
ニュートリノも放出するので、反ニュートリノ流量から熱生成量がわ
K

Th
Th

Th

U
Th

U
Th
Th
Th
Th

Number of anti-neutrinos per MeV per parentTh

Pb + 8 + 6e + 6¯
⇥e + 51.7 MeV

1

238

232
40

100

カムランドは、ウラン、トリウムからの反電子ニュートリノに感度があ10
2005年には、地球反ニュートリノを観測できることを-1

collaboration, “Experimental investigation of geologically produced antineutrinos with Kam
Th KamLAND
Nature 436, 03980 (2005)

U
Th

10-2

0.5

1

1.5
2
2.5
Anti-neutrino energy, Eν (MeV)

3

3.5

Only geo-neutrinos from
U and Th are detectableU‣Geo-neutrino Flux at Kamioka

7/20

Distance and Cumulative Flux
×106ref) Enomoto et al. EPSL 258, 147 (2007)

sedimentcrust
mantletotal

3Total 100

半径ごとの積算フラックス＜５００km

こんなイメージ

Crust 80

５０％
60

2

Mantle140

Percentage of total (%)

Cumulative flux (1/cm2/sec)

4

実際にどのあたりを見ているか
Contributions from each part

Crust : 70%
Mantle : 27%
Core : 0%

20

Sediment etc. : 3%

Sediment
0 0
10

101

102
103
Distance from KamLAND (km)104

0neutrino oscillation

1fromContributions
each areasin2 2✓
P (E, L) ⇠ 1(constant suppression)

半分が半径 500 km から- 50%: distance 2< •500km• 1/4originatesが半径 50 km
から 500 km
50%
ofdistancethe total
flux
within- 25%:< 50km• 1~2% が神岡鉱山から
12- 1~2%: from Kamioka mine

Important •to1/4 がマントルからunderstand Japanesegeology~500 km~50km

targetNATURE
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GEOSCIENCE
DOI: 10.1038/NGEO1205
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2000

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2004

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mated by the two-flavour oscillation formula,

160

140

Events/0.2 MeV

216

LS purification

120

2006

2008

100
80
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40
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KamLAND data

8/20

low reactor phase

2010

2012

ARTICLES2014
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NATURE GEOSCIENCE
DOI: 10.1038/NGEO1205
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Figure 4 | Measured
geoneutrino
flux and models.
a, Measuredheat
valuesof theneutrino
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dni (E⌫ )/dE⌫ is the ⌫ e energy spectrum for+best–fit
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ν
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Figure 1 | Prompt energy
spectrum andselection efficiency.
ecay,
ai (r ) is geoneutrinos
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andHawaii
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the abackgrounds,
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detected.
to the 2✓
phenomenonof oscillation
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and modelTh(green)99.7%
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contours
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Background-subtracted
spectrum.
thefluxesa fully
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2013. For thepresent purpose, the ⌫ e survival
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NATUREJOBS
Highlight India

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GLOBAL CLIMATE
Vital CO2 flux from
Amazon vegetation

BREAST CANCER
Gene signature
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FORENSIC SCIENCE
Everything has
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INSIDE:INDIAN LIFE SCIENCES

Geoneutrinos reveal Earth’s inner secrets

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28 July 2005 | www.nature.com/nature | £10

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Contents

1. KamLAND
2. Geo-neutrino Measurements
3. Analysis Results
4. Summary‣ Current Data-set

9/20

Reactor Neutrino Flux @Kamioka
×10

Neutrino flux (10 neutrino/cm2/day)

12
0.12

12

March ‘11 earthquake

Data provided according to the special agreements between
Tohoku Univ. and Japanese nuclear power reactor operators.

Total
Wakasa-bay
Kashiwazaki
Shika
Hamaoka
Korea
Others

10
0.1

8
0.08

10

updateall Japanesereactor-off period

6
0.06

reactor neutrino

low-reactor period
geo-neutrino

4
0.04

2
0.02

00
03/07

12/25

Reactor neutrino background isdecreased significantly.

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Preliminary

PRD 88, 033001 (2013)2013 data-set : 2991 days
4.90×1032 proton-year2016 data-set : 3901 days
6.39×1032 proton-year-

advantages { -1.3 times of 2013 data-set
low-reactor operation period : ~3.5 years livetime
all Japanese reactor-off period : ~2.0 years livetime

Precise understanding of reactor neutrino spectrum enhances geo-neutrino measurement.

‣Reactor Neutrino Spectrum
Chinese Physics C

covariance matrix, which is calculated by both toy MC
sampling method, and standard error propagation withmatrices. Figure 29 shows the correlation matrix of thegeneric (DayaspectrumBay,
and arXiv:1607.05378v1)
its component uncertainties.

anti-neutrino spectrum
(A)

0.15

0.1

0.05

0
1.2

2 (B)

3

4

5

6

7

antineutrino experiment A; and Smod are the isotope
antineutrino spectra from models, such as ILL+Vogel,
Huber+Mueller,
etc.PSA experiments
could then replace reported
the isotope
Reactorneutrino
spectra related part i Smodi ei in the calculation of the
that
there
was presented
an excesseventsspectrumprediction
in Sec. of
2. Theidea of inthistheapplicationon the condition that the e↵ective
regionofdepends
4-6 MeV.
fission fractions of di↵erent reactor antineutrino experi- Daya Bay, RENO, Double Chooz
ments,
Pi.e. fdyb and fA are small; therefore, corrections
from i (fAi fdybi )Smodi would be relatively small, andSA will be dominated by the measurement result Sdyb
rather than reactor models.

Reactor neutrino spectrum for KamLAND
analysis
0.2
2013 paper: Huber + Mueller & Bugey-4
normalisation
1
8
total
0.8
2016 preliminary: Daya Bay
measurement
result7
detector
0.6
background6
2/fission)-43 (uncertainty
0.4
0.15
σf (cm= (5.92±0.12)×10: 2.03%)
stat
5

8

1

8

1
0.8
1.04
1.02
1
0.98
0.96

Daya Bay / prediction (Huber+Mueller)
2

2

(C)

3

3

4

4

5

5

6

7

8
Antineutrino Energy (MeV)678
Antineutrino Energy (MeV)

Fig. 28. (A) The antineutrino
spectrum weighted
excessby the IBD cross section. The last bin is ingeo-neutrino
tegrated up to 12MeV. (B) Ratio of the exenergy
regionantineutrino spectrum to the Hutracted reactor
ber+Mueller prediction. The error bars of thedata points are the square-roots of the diagonal
elements of the antineutrino spectrum covariance-

Fractional uncertainty

6+8AD/6AD

Data / Prediction

cm2 / fission / MeV × 10-42

0.2

10/20

Vol. XX, No. X (201X) XXXXXX

1

0.8

0.8

0.6

0.6

6

reactor

0.4

0.4

0.2
0.2
0
00
−0.2
−-0.2
0.2
−0.4
0.2

44
3

0.1

22
22 3

We confirmed that :4-6 MeV excess has no impact on the
0.05
geo-neutrino results.
effect of reactor spectrum uncertainty is0
2 smaller
3
4
5the statistical
6
7
8
much
than
Antineutrino Energy (MeV)
uncertainty of geo-neutrino events.
4
4

5 66

7 88

Antineutrino Energy (MeV)

Fig. 29. Uncertainty components of generic spectrum. The inner plot shows the correlation matrixof the generic spectrum.

Period 2: May 2007 - Aug. 2011 (after LS purification)
2005

beforeLS purification(a) 0.9-2.6
MeV
Period 1

2007

Period 2

Period 3

Period 2

KamLAND-Zenconstruction

0.4

0.2

0

Preliminary

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Year

KamLAND data
Expected reactor ν e + backgrounds + geo ν eExpected reactor ν e + backgrounds
Expected reactor ν e

2003

2010

2011

2012

Period 3

0.5

March 2011
0.4
Earthquake

0.3

0.1

002

2009

0

Year after KamLAND-Zen start 2016 Preliminary Result
after LS purification
low reactor period
2.6 < Ep < 8.5 MeV
0.6

Period 1

0.5

2008

LS purification

Rate (events/day)

8.5 MeV
0.6

2006

0.3
0.2

1

0.9
0.8

0.7

0.6

KamLAND-Zen
Preliminary
0.5
start

0.1
0

Observed Rate (events/day)2004

Observed Rate (events/day)2003

LS purification

002

O

1 days‣Event Rate
PeriodTime
3: Oct.Variation2011 - Nov.(0.9-2.6
2012 (afterMeV)
KamLAND-Zen 11/20
start)

0.1

0.2

0.3

0.4

0.5

Expected Rate (events/day)constant contribution of
geo-neutrino

0.6

reactor anti-neutrino +other backgrounds

0.4

0.3

0.2

0.1
0

2005 : 2006
2007
2008
2009
2010
2011
2012
- 2004
Backgrounds
Year backgrounds reduction
LS purification → non-neutrino
long-term shutdown
Earthquake → reactor neutrino reductionof Japanese reactor- Constant contribution of geo-neutrino
evolution of expected
and observed rates at KamLAND for ν ’s with energies betw
Time information is useful to extract the geo-neutrinoe signal

8.5 have
MeV. The
points indicate
the measuredwith
rates in aexpectedcoarse time binning,
while the curta
good
agreement
rateblack line), reactor ν e ’s + backgrounds (colored line), and reactor ν e ’s + backgrounds

Efficiency (%)‣Energy Spectrum (0.9-2.6 MeV)
model prediction : Enomoto et al. EPSL 258, 147 (2007)

100
80
60

Selection efficiency
Data - BG - best-fit reactor νeReference geo νe
U contribution
Th contribution

60
40

Events / 0.2MeV

12/20

2016 Preliminary Result
Livetime : 3900.9 days

20

Candidate : 1130 ev

0

Background Summary

180

KamLAND data

160

Preliminary

Best-fit reactor νe
Accidental

9Li

140
120
100
80

13

16

C(α, n) O

60Best-fit geo νe40Best-fit reactor νe + BG
+ best-fit geo νe

20
0
1

1.2

1.4

1.6

1.8

Ep (MeV)

2

2.2

2.4

2.6

Accidental
Fast neutron
13C(α, n)16O
Reactor νe

3.4 ± 0.1
114.0 ± 0.1< 4.0
205.5 ± 22.6
618.9 ± 33.8

Total

941.8 ± 40.9

‣Energy Spectrum, Period 3 (0.9-2.6 MeV)

13/20

Livetime : 1259.8 days 2016 Preliminary Resultmodel prediction : Enomoto et al. EPSL 258, 147 (2007)10
50Best-fit reactor νe
Accidental13
C(α , n)16O
Best-fit geo νeBest-fit reactor νe + BG
+ best-fit geo νeEvents / 0.1MeV

KamLAND data15

10

PRD 88, 03301 (2013)
0.025

Events/0.2MeV/day

Data - BG - best-fit reactor νeReference geo νeLivetime : 351 days

0.02
0.015
0.01
0.005
0

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

Ep(MeV)

Preliminary

50

We measured clear distributionof geo-neutrino events.
1

1.2

1.4

1.6

1.8

2

Ep (MeV)best-fit : Period 3 analysis

2.2

2.4

2.6

‣Rate + Shape + Time Analysis (1)NU vs NTh

68.3%

earth model prediction
EPSL 258, 147 (2007)

150

Preliminary

NU

95.4%

10

99.7%

PreliminaryNTh2016 Preliminary Result

ratio fixed 15

3σ

∆ χ2

200

14/20

5

2σ

ratio fixed

100

1σ

0

NTh

0

10

50

100
NU

150

3σ

Preliminary

8

∆ χ2

50

6
2σ

4

0

200

0

ratio fixed

50

U
Th

100
NU

150

200

2

1σ

0

0
50
model prediction : Enomoto et al. EPSL 258, 147 (2007)[event][TNU]

128 +46/-39
32 +27/-23

27.1 +9.8/-8.3
6.9 +5.9/-5.0

100
NTh

Flux [×105 cm-2s-1]
0 signal
best-fitmodel rejection
20.8 +7.5/-6.4
22.0
3.44σ
17.2 +14.5/-12.5
18.6
1.34σ

150

‣Rate + Shape + Time Analysis (2)NU + NTh250

ratio fixed(a) Preliminary

200

15/20
2016 Preliminary Result(b) Preliminary

60

8σ

68.3%

150

99.7%

40

6σ

∆ χ2

NU + NTh

95.4%

100

20
50

4σ

earth model prediction
EPSL 258, 147 (2007)

2σ

0
−1

−0.5
0
0.5
(NU - NTh) / (NU + NTh)

1

0

0

50

100
150
NU + NTh

200

250(NU, NTh) = (130, 34)
best-fit N +N = 164
U
Th
model prediction : Enomoto et al. EPSL 258, 147 (2007)
Flux [×106 cm-2s-1][event]ratio fixed[TNU]
best-fit

U+Th 164 +28/-25 (17%) 34.9 +6.0/-5.4 3.9 +0.7/-0.6

0 signalmodel rejection

4.1

7.92σ

‣Th/U Mass Ratio (1)-According to geochemical studies, 232Th is more abundant than 238U.
Mass ratio (Th/U) in bulk silicate Earth is expected to be around 3.9.
Models : 3.58-4.2

-

16/20

4.2 : Allegre et al. (1986)
3.92 : McDonough & Sun (1995)
3.89 : Taylor (1980)
3.85 : Anderson (2007)
3.77 : Palm & O’Neil (2003)

3.76 : Hart & Zindler (1986)
3.71 : Lyubetskaya & Korenaga (2007)
3.62 : Jagoutz et al (1979)
3.58 : Javoy et al. (2010)Chondrite samples analysis : 1.06-6.42
Fall statistics for the meteorites identified
and catalogued since 980 A.D.

-

Geo-neutrino observed rate can beconverted to amount of Th & U
assuming homogeneous distribution.
Independent & direct measurementof entire Earthslide from McDonough, 2015, in Ehime‣Th/U Mass Ratio (2)17/202016 Preliminary Result

Th/U=3.9
chondrite data
(1.06-6.42)

3

Best fit
90%

BSE models(3.58-4.2)

Th/U = 4.1 +5.5-3.3
Th/U < 17.0 (90% C.L.)ref) 2013 paper Th/U < 19 (90% C.L.)

∆ χ2

2

We have a sensitivity of
Th/U mass ratio of entire
Earth.

1σ

1KamLAND best-fit isconsistent with chondrite
data and BSE models.

Preliminary
0

0

5

10
15
Th/U mass ratio

20ref) chondrite data
Ordinary Chondrites : J. S. Goreva & D. S. Burnett, Meteoritics & Planetary Science 36, 63-74 (2001)
Carbonaceous Chondrites : A. Rocholl & K. P. Jochum, EPSL 117, 265-278 (1993)
Enstatite Chondrites : M. Javoy & E. Kaminski, EPSL 407, 1-8 (2014)

‣Earth Model Comparison

18/20
PRD 88, 03301 (2013)

νe Flux (× 106 cm-2s-1)

Geodynamical

6

Geochemical
Cosmochemical

4
KamLAND 68.3% C.L.

2

crust uncertainty

Preliminary
0
0

10
20
30
Radiogenic Heat from 238U + 232Th (TW)

Cosmochemical Geochemicalie Flux (× 106 cm-2s-1)

2016 Preliminary Result

Geodynamical

6

4
KamLAND 68.3% C.L.

2

0
0

10
20
30
238
232
Radiogenic Heat from U + Th (TW)

[BSE composition models]
Geodynamical
based on balancing mantle
viscosity and heat dissipation

Geochemical
based on mantle samples comparedwith chondrites

Cosmochemical
based on isotope constraints andchondritic models‣Future Prospect

19/20

Uncertainty of Geo-neutrino Flux Measurement
Uncertainty of geo-neutrino flux
measurement is decreased at the samelevel of our expectation.

Simulation(assuming Earth model)

reactor “ON”

Measurement uncertainty gets close touncertainty of Earth model prediction.

reactor “OFF”

It is important to improve accuracy ofEarth model prediction, especially crustmodelling.

+ 2.5 yr2016 Preliminary

PRD 88, 03301 (2013)

(b)
60

~21%

8σ

fit with ± 1σ
Preliminary * best+0.7
6

3.9

40

/cm2/s : ~18%

∆ χ2

6σ

20

4σ

* uncertainty of Earth model prediction : 20%2σ0-0.6×10

0

50

100
150
NU + NTh200

250

‣Summary

20/20‣The KamLAND experiment measures anti-neutrino from various sources
over a wide energy range.

‣Preliminary results are presented.
Low-reactor operation period : ~3.5 years (33% of total livetime), clear
energy spectrum of geo-neutrino- geo-neutrino event measurement with 17% uncertainty (164 +28-25 ev).
It is consistent with our expectation.
- geoscience discussion- Th/U mass ratio : 4.1 +5.5-3.3, consistent with chondrite data and BSE
models- Observed flux : consistent with models, but started to disfavour
cosmochemical model-‣Measurement uncertainty gets close to the uncertainty of Earth model
prediction.

‣Next target :- Estimation of geo-neutrino contribution from mantle- Better understanding of crust model