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