Status and Prospects of KamLAND 1000m KamLAND BO 50% dodecane - - PowerPoint PPT Presentation

Status and Prospects of KamLAND

Kunio Inoue Research Center for Neutrino Science, Tohoku University

Windows to new paradigm in particle physics, 14-16 February 2005, Sendai, Japan

O N

1.5g/l

HHHHHHHHHHHH HCCCCCCCCCCCCH HHHHHHHHHHHH

80%

CH3 CH3 CH3

20%

LS

Water Cherenkov Outer Detector

LS

Buffer Oil photo-coverage 22% --> 34%

BO

50% dodecane 50% isoparaffin

KamLAND

1000m

358 m 36◦2535.562 137◦1843.495

long. lat. alt.

1200 m3 1800 m3 20 m 3200 m3

ρ = 0.78 g/cm3

8000 photons/MeV

λ ∼ 10 m

ρLS ρBO = 1.0004 ∼ 500 p.e./MeV

1325 17”-PMTs + 554 20”-PMTs (since Feb 2003)

0.4 1.0 2.6 8.5 Visible energy [MeV]

Neutrino Astrophysics verification of SSM Neutrino Geophysics verification of earth evolution model Neutrino Physics Precision measurement

• f oscillation parameters

Neutrino Cosmology verification of universe evolution

7Be solar neutrino

geo-neutrino reactor neutrino supernova relic neutrino etc.

Various Physics Targets with wide energy range

1st results PRL 90, 021802 (2003) 2nd results hep-ex/0406035 Solar PRL 92, 071301 (2004)

¯ νe

forthcoming future 2nd phase neutrino electron elastic scattering inverse beta decay

ν + e− → ν + e−

¯ νe + p → e+ + n

Reactor neutrino detection

prompt signal delayed signal with a help of inverse reaction

¯ νe + p → e+ + n

n + p → d + γ(2.2 MeV)

e+ + e− → 2γ

τ ∼ 210 µsec

Eth = (Mn + me)2 − M 2

p

2Mp = 1.806 MeV

Evis ∼ Eν − 0.78 MeV

> 1.022 MeV

¯ νe ~99.999% (E > 1.8 MeV)

n → p + e− + ¯ νe

σ(¯ νep)

is calculable at 0.2% accuracy.

σ(0)

tot = 2π2/m5 e

f R

p.s.τn

E(0)

e p(0) e

τn = 885.7 ± 0.8 sec

P .Vogel and J.F.Beacom, Phys.Rev.D60(1999)053003 A.Kurylov et al., Phys.Rev.C67(2003)035502

10

• 5

10

• 4

10

• 3

10

• 2

10

• 1

1 1 2 3 4 5 6 7 8 9 10 Energy (MeV) neutrinos/MeV/fission

238U 239Pu 235U 241Pu

measured at ILL 30 hypothetical beta fit

K.Schreckenbach et al., Phys.Lett.B160(1985)325 A.A.Hahn et al., Phys.Lett.B218(1989)365

theoretical 744 traces

P .Vogel et al., Phys. Rev. C24(1981)1543 M.F.James, J.Nucl.Energy 23(1969)517

235U : 201.7, 238U : 205.0, 239Pu : 210.0, 241Pu : 212.4MeV

∼ 2 × 1020 ¯ νe/GWth/sec

~95.5% from Japan ~3.5% from Korea 70 GW (7% of world total) is generated at 130-220 km distance from Kamioka.

from 2006 LMA parameters

Neutrino oscillation study with spread reactors

effective distance ~180km

(weighted average by event rate up to 400 km)

∼ 6 × 106/cm2/sec Reactor neutrino flux,

(2nd result period)

Date 3/3 1/30

fission/s)

19

Fission rate (10

1 2 3 4 5 6 7 8

x10

2002

2003

A typical 1.3GWe class BWR in Japan

1 2 3 4 5 6 7 8

U235 U238 Pu239 Pu241

Burn-up is calculable from history of thermal power, fraction of new fuel and 235U enrichment.

Date

3/7 1/23

Ratio of fission flux 0.2 0.4 0.6 0.8 1 1.2

2002

2003

Ratio of the fission flux for each isotope at KamLAND

)

/day)/(MW/cm

event/cm

• 21

Event rate flux per thermal power flux(10

0.2 0.4 0.6 0.8 1 1.2

U235 U238 Pu239 Pu241

235U :239 Pu :238 U :241 Pu =

0.563 : 0.301 : 0.079 : 0.057

(average over second result period)

Distance(km) 100 200 300 400 500 600 700 800 900 1000

1000 2000 3000 4000 5000 6000 7000

x10

)

2

fission/cm

12

Fission number flux(10 2 4 6

235U 239Pu 238U 241Pu

Detailed information from Japanese reactors History of electric power output from Korean reactors Nominal power from the other reactors 95.5% 3.4% 1.1%

Date 3/7 1/23 /day)

2

neutrino/cm

10

Neutrino flux (10

0.2 0.4 0.6 0.8 1 1.2

11

x10

Mar Apr May Jun

2002

Jul Aug Sep Oct Nov Dec Jan Feb Mar

2003

Apr May Jun Jul Aug Sep Oct Nov Dec

Neutrino flux (1.8-8MeV) at KamLAND from reactors

2 4 6 8 10 12 Total

Wakasa-bay Kashiwazaki Others Shika Hamaoka Korea

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

Data Summary

from March 4 to October 6, 2002 145.1 live days, 162 ton-year exposure

Analysis threshold 2.6 MeV

expected signal BG

• bserved

86.8 ± 5.6 54

Neutrino disappearance at 99.95% CL.

R = 0.611 ± 0.085(stat) ± 0.041(syst)

KamLAND collaboration, Phys.Rev.Lett.90(2003)021802

1 ± 1

1st result

1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Nobs/Nno_oscillation 101 102 103 104 105 Distance to Reactor (m)

ILL Savannah River Bugey Rovno Goesgen Krasnoyarsk Palo Verde Chooz

KamLAND

Evidence for reactor neutrino disappearance

2 gen. Neutrino oscillation parameters consistent with each solar results with KamLAND rate

RSFP FCNC decay decoherence etc.

tan2() m2 in eV2 10-12 10-11 10-10 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10-4 10-3 10-2 10-1 1 10 10 2

Ga Cl SuperK SNO

LMA SMA LOW VAC LMA SMA LOW RSFP FCNC decay decoherence etc. VAC Reactor neutrino disappearance excluded all but LMA from leading phenomena.

Analysis Improvements

Fiducial volume was enlarged thanks to more uniform energy scale and less vertex bias. Coincidence criteria were loosened to increase detection efficiency focusing on reactor neutrinos.

78.3% --> 89.8% factor 1.15

And more run time.

5m --> 5.5m factor 1.33

02 03 04 05 06 07 08 09 10 1112 01 02 03 04 05 06 07 08 09 10 1112 01 hour 2 4 6 8 10 12 14 16 18 20 22 24 2002 2003 2004 LiveTime [day] 100 200 300 400 500 600

Physics Run Calibration Run (source,laser and LED) Test/Bad Run

1st result 4 Mar 2002 - 6 Oct 2002 145.1 days 2nd result 9 Mar 2002 - 11 Jan 2004 515.1 days

X 3.55 live time

Finally, lower reactor operation X 0.77 Statistical improvement --> X 4.2

Jul/02 Jan/03 Jul/03 Jan/04 (events/day)

no-oscil exp

N 0.2 0.4 0.6 0.8 1 1.2 Weighted distance(km) 150 160 170 180 190 200 210

no-oscil exp

N Weighted distance Period for first result

Energy Calibration with Radioactive Sources

1 10 10

10

10

10

n+p→D+γ n+12C→13C+γ

12B etc.

0 2 4 6 8 10 12 14 16 Energy (MeV) deviation[%]

• 3
• 2
• 1

1 2 3 Mar Apr May Jun Jul Aug Sep

spallation neutron

(proton capture)

with Muon Spallation

z-axis[cm]

• 600
• 400
• 200

200 400 600 deviation of E[%]

• 5
• 4
• 3
• 2
• 1

1 2 3 4 5 Co Zn z-axis dependence of energy Zn

Ge

500 1000 1500 2000 2500

visible energy (MeV)

4 6 8 10 12 14 16

0.2 0.4 0.6 0.8 1 1 2 3 4 5

n-p n-

visible energy (MeV)

1 2 3 4 5 6 7 8 9

• 0.04
• 0.02

0.02 0.04

Energy (MeV) E/E ∆

• ray sources

γ decay β Ge

68

Co

60

Zn

65

n-p C

12

n- N

12

B/

12

Energy scale error at 2.6 MeV Cherenkov/Birks Time dependence Position dependence 20” PMT non-linearity Total 1.0% 1.3% 1.0% 0.8% 2.0%

with 20” PMTs

σ E ∼ 6.2% √ E

without 20” PMTs

∼ 7.5% → ∼ 7.3%

Fiducial Volume Calibration with Radioactive Sources with Muon Spallation

z-axis[cm]

• 600
• 400
• 200

200 400 600 z deviation[cm]

• 10
• 5

5 10 Co Zn

Ge Am/Be(4.4MeV) Am/Be(~7.6MeV)

σx,y,z ∼ 20cm √ E

with 20” PMTs

0.2 0.4 0.6 0.8 1 1.2 1.4 500 1000 1500 2000 2500 3000 3500 4000 fiducial balloon radius

3

(R/6.5m) Events/Bin

0.2 0.4 0.6 0.8 1 1.2 1.4 200 400 600 800 1000 fiducial balloon radius

3

(R/6.5m)

3

(delayed R/6.5m) 0.2 0.4 0.6 0.8 1 1.2 prompt R - delayed R [cm]

• 150
• 100
• 50

50 100 150 Li (prompt energy>4MeV)

9

He

8

fiducial

12B

delayed coincidence

Fiducial/Total Volume Ratios

geometrical

12B

p(n, γ)d

0.595 ± 0.013 0.607 ± 0.006 ± 0.006 0.587 ± 0.013

9Li relative

< 2.7%

conservative volume error 4.7%

p(n, γ)d

9Li

• =

696.9 m3 1171 ± 25 m3

• β + n

So far Achieved Systematic Errors

6.5 Total 0.2 Cross section 2.5 νe spectra 1.0 Fuel composition 2.1 Reactor power 0.06 Livetime 1.6 Efficiency of cuts 2.3 Energy threshold 4.7 Fiducial volume % Systematic

5 10 15 20 25 30 35 40 45 50

• 8
• 6
• 4
• 2

2 4 6 8

prompt )

2

(m

2

+y

2

x z (m)

5 10 15 20 25 30 35 40 45 50

• 8
• 6
• 4
• 2

2 4 6 8

delayed )

2

(m

2

+y

2

x z (m)

Event Selection

delayed coincidence

∆R < 2m

(neutron capture)

Rprompt, delayed < 5.5m

fiducial volume spallation cuts ∆Tµ < 2msec ∆Tµ < 2sec

Eextra > 3GeV

• r ∆L < 3m

reactor energy window

dead time 9.7% (11.4%)

2.6 < Eprompt < 8.5 MeV

1.8 < Edelayed < 2.6 MeV

0.5 < ∆T < 1000 µsec

(660 µsec)

(1.6 m)

(5.0 m)

543.7 ton

(408.5 ton)

Np = 4.61 × 1031 (3.46 × 1031)

(showering)

Total detection efficiency 89.8% (78.3%)

Delayed vs. Prompt Energy

1 6 5 4 3 2 10 2 3 4 5 6 7 8

delayed energy window Delayed Energy (MeV) Prompt Energy (MeV)

12C(n, γ)

1st result

clear coincidence events

(MeV)

delayed

E

2 3 4 5

(MeV)

prompt

E

1 2 3 4 5 6 7 8

12C(n, γ) expected

1.5 accidental

2nd result

1.8 < Edelayed < 2.6 MeV

2.6 < Eprompt < 8.5 MeV

Backgrounds

Accidental Coincidence

0.0086 ± 0.00005

1st result (5m fiducial 162 ton-yr)

2.69 ± 0.02

2nd results (5.5m fiducial 766.3 ton-yr)

prompt energy [MeV] 1 2 3 4 5 6 7 8 9 10 counts/20keV 10

• 1

1 10 10

2

10

3

10

4

10

5

10

6

208Tl from wall 210Bi in LS

analysis threshold

Fiducial volume is limited by accidental backgrounds.

energy [MeV] 2 4 6 8 10 12 14 counts/bin 10 20 30 40 50 60

9Li > 85% (90%CL)

detection eff. 98.7%

Spallation events

2 sec VETO for all volume

350 → 0.1

Eextra > 3GeV

2 sec VETO for 6mφ cylinder 93.8% eff.

86 → 5.7

Eextra < 3GeV

9Li

T1/2 = 0.18 sec

9Be 8Be + n

β n

total 50%

4.8 ± 0.9 events (E > 2.6 MeV)

(2nd result)

Fast neutron

OD miss-tagging rock penetrating Total <0.4 <0.5 <0.9

recoiled proton + neutron capture

sec] µ T [ ∆ 500 1000 1500 2000

10 20 30 40 50 60 70 80

delayed energy [MeV] 1.6 1.8 2 2.2 2.4 2.6 2.8 3

10 20 30 40 50 60 70

prompt radius [cm]

100 200 300 400 500 600 700 800 10 20 30 40 50

5m 5.5m

prompt energy [MeV] 2 4 6 8 10 12 14

5 10 15 20 25 30 35 40

fiducial

Tagged events

R-distribution prompt energy time difference delayed energy

(2nd result)

222Rn (3.8d) 218Po 214Pb 214Bi 214Po 210Pb (22.3y) 210Bi (5.013d) 210Po (138.4d) 206Pb (stable)

equilibrium

(Eα = 5.3MeV )

10.3±7.1 events (E>2.6MeV)

Visible Energy (MeV) 0.2 0.4 0.6 0.8 1 1.2 1.4 Events/MeV/sec 10

• 4

10

• 3

10

• 2

10

• 1

1 10 10

2

10

3

10

4

85Kr 210Po 210Bi

1.1% abundance (measured)

13C(α, n)16O

∼ 10−7

13C + α 17O 16O + n

210Po α

max

internal pair conversion

6.36 4.14

0.87 3.06 3.84 4.55

6.05 6.13

6.92

γ

13C(α, n)16O(g.s.) 13C(α, n)16O∗(6.05) 13C(α, n)16O∗(6.13)

→12 C(n, nγ)12C

13C(α, n)16O(g.s.)

low energy ~4.4 MeV ~6 MeV

Low energy spectrum

Background summary

Accidental Coincidence

2.69 ± 0.02

Spallation events Fast neutron

13C(α, n)16O

4.8 ± 0.9 < 0.9 10.3 ± 7.1

Total

17.8 ± 7.3

515.1 days, >2.6MeV, 5.5m fiducial

Data Summary

from 9 Mar 2002 to 11 Jan 2004 515.1 live days, 766.3 ton-year exposure expected signal BG

• bserved

Neutrino disappearance at 99.998% CL.

KamLAND collaboration, hep-ex/0406035

365.2 ± 23.7 258

for Mar to Oct 2002 is consistent with first results

2nd result

Data Summary

from March 4 to October 6, 2002 145.1 live days, 162 ton-year exposure expected signal BG

• bserved

86.8 ± 5.6 54

Neutrino disappearance at 99.95% CL.

KamLAND collaboration, Phys.Rev.Lett.90(2003)021802

1st result

×4.7 exposure (×3.55 live time, ×1.33 fiducial)

17.8 ± 7.3

R = 0.658 ± 0.044(stat) ± 0.047(syst)

R = 0.601 ± 0.069 ± 0.042

R = 0.589 ± 0.085(stat) ± 0.042(syst)

with new background correction

2.8 ± 1.7

expected (no oscillation)

• bserved

追加

Event list and relevant numbers are available at http://www.awa.tohoku.ac.jp/KamLAND/datarelease/2ndresult.html

expected (no oscillation)

• bserved

Expected and observed time variation

Event rate (event/fiducial/day) 0.2 0.4 0.6 0.8 1 Detected Rate Expected Rate Mar Apr May Jun Jul Aug Sep

rate (events/day)

e

• no-osc

0.2 0.4 0.6 0.8 1 1.2

rate (events/day)

e

• bserved

0.2 0.4 0.6 0.8 1 1.2 0.2 0.4 0.6 0.8 1 1.2 0.2 0.4 0.6 0.8 1 1.2 Data Background

09 Mar '02 19 Oct '02 31 May '03 11 Jan '04

rate (ev/d)

• no-osc

0.3 0.6 0.9 1.2

Correlation with reactor power

95% CL

χ2/dof = 2.1/4

constrained to expected BG n

• s

c i l l a t i

• n

χ2

flat = 5.4

data division scheme

Current statistics is not enough to say definite thing.

Recent extensive inspection may provide another chance to investigate the correlation.

04 05 06 07 08 09 10 11 12 01 02 03 04 05 06 07 08 09 10 11 12 01 02 03 04 05 06 07 08

)

2

MW/cm

• 12

Electric power flux (10 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

• 10

10

• Electric power flux at KamLAND

1 2 3 4 5 6 7 8 9 10

JAIF data

2002. 2003. 2004.

？

2nd result

Prompt Energy (MeV) Events/0.425MeV

KamLAND data no oscillation scaled no osc. accidental

2 4 6 8 20 40 60 80

spectral distortion at >99.6% CL rate + shape 99.999995% CL

hypothesis test of scaled no oscillation

for 20 equal probability bins

goodness of fit (MC)

0.4%

Energy Spectrum

χ2/dof = 37.3/19

• scillation

Best fit parameters χ2/dof Model GOF

11.1% decay 0.7% decoherence 1.8%

Significant spectral distortion supports neutrino oscillation.

equal probability 20 bins MC based by unbin-likelihood method

Prompt Energy (MeV) Events/0.425MeV KamLAND data no oscillation best-fit oscillation accidental O

16

, n)

• C(

13

1 2 3 4 5 6 7 8 20 40 60 80

(sin2 2θ, ∆m2) = (0.86, 7.9 × 10−5 eV2)

35.8/17 32.2/17 24.2/17

(sin2 2θ, γ) = (1.0, 0.030 MeV/km) (sin2 θ, m2/cτ) = (1.0, 0.011 MeV/km)

20 30 40 50 60 70 80

/E (km/MeV) L Ratio

2.6MeV analysis threshold KamLAND data best-fit oscillation best-fit decay

1

0.2 0.4 0.6 0.8 1 1.2 1.4 10

• 3

10

• 2

10

• 1

1

ILL Goesgen Savannah River Palo Verde CHOOZ Bugey Rovno Krasnoyarsk

best-fit decoherence

• scillation

decay decoherence

Pee = 1 − sin2 2θ sin2(∆m2 4 L E )

Pee = (cos2 θ + sin2 θ exp(−m2 2τ L E ))2 Pee = 1 − 1 2 sin2 2θ(1 − exp(−γ L E ))

L0=180km is used for KamLAND ideal

• scillation

pattern with real reactor distribution

Clear oscillation pattern has been seen.

0.2 0.4 0.6 0.8 1 10

• 6

10

• 5

10

• 4

10

• 3
• 2

2

sin )

2

(eV

2

m

• Solar

95% C.L. 99% C.L. 99.73% C.L. Solar best fit KamLAND 95% C.L. (Rate) 95% C.L. 99% C.L. 99.73% C.L. KamLAND best fit

Measurement of neutrino oscillation parameters

comparison with 1st results (95%CL) LMA0 LMA1 LMA2 97.5% 98.0% 62.1%

mνe <

• mνµ
• mνe >
• mνµ
• matter effect makes small difference

10

• 1

1 10 10

• 5

10

• 4
• 2

tan )

2

(eV

2

m

• Solar

95% C.L. 99% C.L. 99.73% C.L. solar best fit KamLAND 95% C.L. 99% C.L. 99.73% C.L. KamLAND best fit

best fit rate+shape best fit shape-only (tan2 θ, ∆m2) = (0.46, 7.9 × 10−5 eV2) (tan2 θ, ∆m2) = (0.76, 8.0 × 10−5 eV2)

0.2 0.3 0.4 0.5 0.6 0.7 0.8 5 6 7 8 9 10 11 12

• 5

10

• 2

tan )

2

(eV

2

m

• KamLAND + Solar

95% C.L. 99% C.L. 99.73% C.L. global best fit

Assuming CPT invariance

Precise determination of oscillation parameters made possible to use neutrinos as a new probe.

∆m2 = 7.9+0.6

−0.5 × 10−5 eV2

tan2 θ = 0.40+0.10

−0.07

several orders -> less than 10%

Karsten Heeger, LBNL Sendai, September

Further improvement of systematic errors

z-axis calibration full volume calibration

Rate information doesn’t have a strong impact on the precision due to large systematic errors.

rate+shape best fit shape only best fit

0.2 0.4 0.6 0.8 1 10

• 6

10

• 5

10

• 4

10

• 3
• 2

sin )

(eV

m

• 0.2

0.4 0.6 0.8 1 10

• 6

10

• 5

10

• 4

10

• 3
• 2

sin )

(eV

m

• (0.86, 7.9 × 10−5)

(0.98, 8.0 × 10−5)

0.2 0.3 0.4 0.5 0.6 0.7 0.8 5 6 7 8 9 10 11 12

• 5

10

• 2

tan )

2

(eV

2

m

• KamLAND + Solar

95% C.L. 99% C.L. 99.73% C.L. global best fit

3% rate error 1% scale error 3kt-yr data accumulation

KamLAND only rate+shape sensitivity

(rough estimation) capability to reject full mixing mixing angle determination comparable with current solar data factor ~2 improvement?

Important motivations

(1) What is the heat source that drives earth dynamics? (2) Is there another way to observe the interior directly?

Geo-neutrino Observation

(No public data yet, sorry)

(1) What is the heat source?

0.0 20.0 50.0 80.0 110.0 mW/m2

Surface Heatflux at 2x2 degrees

Surface heat flow measurement Total flow 44 TW is 40 times of world total reactor power. Combining all the available geo-chemical knowledge, Radioactivity 20 TW

Uranium 8TW, Thorium 8TW, Potassium 4TW

The rests are

residual heat, latent heat, gravitational energy etc. U,Th are condensed in the crust and the earth is something like wrapped in a heat blanket.

Neutrinos from radioactivity provide direct information of the earth’s interior!!

Uranium series Thorium series

Their observation is a “neutrino tomography”

• f the earth.

Verification of the SSM with more abundant neutrinos is important. Real time measurement of low energy solar neutrinos has never been done. It may help improving oscillation parameter measurement. It has good sensitivity on neutrino magnetic moment.

KamLAND Real time measurement

(pp-chain) 98.5% D p→3Heγ

3He 4He→7Beγ 3He 3He→4He p p

13.8% 84.7%

7Bee−→7Liν e(γ)

(7Be)

7Be p→8Bγ

p p → De+ν e pe− p → Dν e

(pp) (pep) 99.77% 0.23% ~2×10-5% 13.78% 0.02%

7Li p→4He 4He 3He p→4He e+ν e

(hep)

8B→8Be* e+ν e 4He 4He

(8B)

7Be ~14% 8B ~0.02% Fusion reaction in the Sun

Toward 7Be Solar Neutrino Observation

(pp-chain) 98.5% D p→3Heγ

3He 4He→7Beγ 3He 3He→4He p p

13.8% 84.7%

7Bee−→7Liν e(γ)

(7Be)

7Be p→8Bγ

p p → De+ν e pe− p → Dν e

(pp) (pep) 99.77% 0.23% ~2×10-5% 13.78% 0.02%

7Li p→4He 4He 3He p→4He e+ν e

(hep)

8B→8Be* e+ν e 4He 4He

(8B)

7Be ~14% 8B ~0.02%

Solar neutrino observation

SK, SNO Chlorine Gallium

10 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10

• 1

1 10

[MeV]

hep

8B

pep

7Be 7Be

pp

13N 15O 17F

10 11 10 12 10 13

[ /MeV /cm 2/sec]

±1% ±12% ±12% ±2% ±23% ±16% ∼ ±40%

KamLAND

Branching ratio to 7Be neutrino is larger and theoretical uncertainty is smaller. Its flux is so far measured at only 40% level.

1 104∼5 1 10∼6

required further improvement

Background now goal

238U(by Bi-Po)

3.5 × 10−18g/g OK!!

238U(by 234Pa)

O(10−15g/g)(Max.) 10−18g/g

232Th (by Bi-Po)

5.2 × 10−17g/g OK!!

40K

2.7 × 10−16g/g(max.) < 10−18g/g

210Pb

∼ 10−20g/g 5 × 10−25g/g ∼ 1µBq/m3

85Kr, 39Ar 85Kr =0.7Bq/m3

1µBq/m3

222Rn 238U = 3.5 × 10−18g/g

OK!! (1µBq/m3)

(after purification)

= 3.3 × 10−8Bq/m3

222Rn

1mBq/m3

(during purification)

210Pb = 0.5µBq/m3 after decay

Visible Energy (MeV) 0.2 0.4 0.6 0.8 1 1.2 1.4 Events/MeV/sec 10

• 4

10

• 3

10

• 2

10

• 1

1 10 10

2

10

3

10

4

Current background level

7Be ν

pp ν

14C 11C 85Kr 210Bi 210Po

daughter of 210Pb

SSM

Purification achievement

• N2 gas purge

N2/LS=25 ---> ~1/10 Rn, ~1/100 Kr

• Fractional Distillation (164℃, 300 hPa)

3×10-5 Pb 1×10-5 Rn <2×10-6 Kr

Residual impurities will be some organic lead (e.g. tetra-ethyl-lead) and they disintegrate at ~200 ℃.

Required performance is almost achieved.

50 100 150 200 250 300 350 400 450 500 400 450 500 550 600 650 700 750

events/keV Energy [keV] KamLAND (expected 3y, R<4m)

7Be ! 210Bi

LMA After statistical subtruction (238U, 232Th) and assume all BG =210Bi(210Pb) 40000 60000 80000 20000 30000

7Be ! 210Bi

SSM +/-3.6%(99%C.L) 5000 10000 15000 20000 25000 30000 0.2 0.4 0.6 0.8 1

counts [350-750keV] L0

2/L2

KamLAND expected (5y, fiducial R<4m)

SUN L; distance from Sun to Earth L=L0(1-!cos(2"t)), !=1.7% Extrapolate L#!$ to estimate BG SSM LMA result from L#!$ limit 0.0 0.2 0.4 0.6 0.8 1.0 1.2 SSM LMA

BG subtraction with shape fit BG subtraction with seasonal variation

500 1000 1500 2000 2500 3000 200 400 600 800 1000

counts/25keV Energy [keV] KamLAND future goal

14C

(assume 14C/12C=10-18)

232Th(5.2x10-17g/g) 11C

(1.0x103 day-1kton-1)

7Be !(SSM) 210Pb

(assume 1!Bq/m3)

39Ar, 85Kr

(assume 1!Bq/m3)

All All ! (SSM)

When the required reduction is achieved,

7Be neutrinos will be seen in the window

between 14C and 11C background.

accurate robust

Summary

Updated results strengthened evidence of neutrino disappearance. Spectral distortion is observed at >99.6% CL. Rate+shape data excluded no oscillation at 99.999995% CL. L/E plot shows clear oscillatory behavior. Oscillation parameters are measured precisely. Forthcoming geo-nu observation will pioneer “Neutrino geo-physics”. KamLAND will push forward “Neutrino Astrophysics” with 7Be solar neutrino observation. (1) (2) (3) (4) (5) (6) (7)

∆m2 = 7.9+0.6

−0.5 × 10−5 eV2

Thank you!