Results and plans of the

KamLAND experiment

Yoshihito Gando (RCνS, Tohoku Univ.)

for the KamLAND Collaboration

ICFP2005 @ Chung-li, Taiwan, 4 October 2005

Nature 436, 28 (2005)

0.4 1.0 2.6 8.5 Visible energy 　 [MeV]

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Neutrino Astrophysics

verification of SSM

Neutrino Geophysics

verification of earth evolution model

Neutrino Physics

Precision measurement of oscillation parameters

Neutrino Cosmology

verification of universe evolution

7Be solar neutrino geo-neutrino reactor neutrino supernova relic neutrinoetc.

Various Physics Targetswith wide energy range

1st results PRL 90, 021802 (2003)2nd results PRL 94, 081801(2005)

Solar PRL 92, 071301 (2004)

future2nd phase

neutrino electron elastic scatteringinverse beta decay

KamLAND detector

Photo - coverage: 34%

~ 500 p.e. / MeV

Cosmic ray 's are suppressed by 1/100,000.

1,000 ton liquid scintillator Dodecane : 80% Pseudocumene : 20% PPO : 1.5g/l

Mineral oil Dodecane : 50% Isoparaffin : 50%

1000m

17 inch :1325

20 inch : 554

20 inch : 225

13m1.75m thickness

~8000 photons / MeVλ: ~10m

ν detection in KamLAND

ep

e+ e

n

p

d

(0.51)

(0.51)

(2.2 MeV)

Prompt e+ signal

Delayed γ by neutron capture• Position

• Time correlation• delayed energy information

Greatly removes backgrounds

E1.8MeV

Te++annihilation

=Eν - 0.8MeV

~210μs

Te+

+ p e+ + ne

e

Reactor Neutrino

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Reactors near the KamLAND

Reactors in Taiwan have ~0.1% contribution.

)cm(MW/ 2ThermalP

80% of total contribution comes from 130~220km distance

Reactor neutrino flux,

~95.5% from Japan~3% from Korea

(2nd result period)

effective distance ~180km

Event SelectionDelayed Coincidence: 0.5 < ΔT < 1000μsec ΔR < 200 cm 1.8 < Edelayed < 2.6 MeV Fiducial Volume:

Rprompt < 550 cm (500 :1st result)

Rdelayed < 550 cm (500 : 1st result)

Prompt Energy Window: 2.6 < Eprompt < 8.5 MeV

9Li

3m

μSpallation Cuts: ΔTμ < 2 msec 　 ΔTμ < 2 sec (showering muons) 　　　　　　　　 or 　　　　 ΔTμ < 2 sec (showering muons)　　　　 ΔL 　 < 300 cm (non-showering)

Isotope Halflives Decay Mode9Li/8He 178.3ms/119.0msβ － + n

Efficiency : 89.82%(I,II), 89.83%(III)

Expected event rate

Observed event rate

Time Variation of Reactor ν

• R = 0.658 ±0.044(stat) ± 0.042(syst) neutrino disappearance at 99.998% C.L.⇒

High statistic from 1st result oscillation study

First resultExpected signal : 86.8±5.6

BG :1±1Observed : 54

Neutrino disappearance at 99.95%

Energy Spectrum

•Hypothesis test of scaled no-oscillation: χ2/ndf = 37.3/18 spectral distortion at > 99.6% C.L.⇒

• Rate + Shape: no oscillation is excluded at 99.999995% C.L.

low energy window best fit reactor +

geo-neutrino model prediction

L/E plot with data for geo-ν analysis(759 days, 5m fiducial)

Oscillation pattern with real reactor

distribution

Lo = 180 km is used for KamLAND

There is clear Oscillatory behavior (peak and dip) oscillation parameter is determined.

Oscillation Analysis

assuming CPT invariance

KamLAND best-fit (rate + shape)

10.007.0

2

256.05.0

2

40.0tan

eV 109.7

m46.0tan

eV 109.72

252

m

KamLAND + Solar

several orders -> less than 10%

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

Geo - Neutrino

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Earth Energetics

• Observed Surface Heat Flow :

～ 44TW (31TW : re-evaluation)• Radiogenic Heart : ~20TW ?

U-chain 8TW / Th-chain 8TW / 40K 3TW??? (BSE model)• Radioactive heat sources contribute to about the half of the

total heat outflow of the earth.• Geo-Neutrino is Produced by β-decay of radioactive eleme

nt in the earth

• Terrible earthquakes, eruptions, etc. are originally caused by mantle convection driven by heat.• Terrestrial magnetism is caused by a core movement, it requires some heat source.

Methods of research about inside of the earth

Seismic analysis

Composition of the earth (Proto material ) is presumed by meteorite analysis

BSE (bulk silicate Earth) model

• Th/U mass ratio ~ 3.9• It expect that 20TW comes from radioactivity• There are no direct measurements

• Physical parameter (density, elastic parameter etc…)• It does not tell chemical composition

Direct measurement is desired!!

McDonough et al.(1995)

Meteorite analysis

Geophysics with Neutrino• Determination of the amount and distribution of U, T

h in the earth from geo-ν observation - Test for BSE model Verification of basic paradigm of geochemical earth formation and generation

- Determination of heat balance Information for earth dynamics, evolution, terrestrial magnetism

- Understanding of chemical composition of deep interior of the earth Determination of chemical structure model (mantle model)

Reference Earth ModelUpper continental crust U : 2.8ppm / Th: 10.7ppm Middle continental crust U : 1.6ppm / Th: 6.1ppm Lower continental crust U : 0.2ppm / Th: 1.2ppm

Oceanic crust U: 0.08ppm / Th: 0.32ppm

U: 0ppm / Th: 0ppm

U: 0.012ppm / Th: 0.048ppm

Rudnick et.al. (1995)

continental crust

Th/U ~3.9Radiogenic heat ~16TW

mantle Core

Mantle = Meteorite (BSE model) - Crust

Ionic radius of U/Th are largeCore is very high density

do not exist

U/Th distribution maps in JapanAverage component of upper continental crustGeological map + rock sample (Togashi et al.)

U : 2.32 ppm Th : 8.3 ppmAssume the surface U, Th distribution extends to 5km in depth

Geo-neutrino flux is calculated from global and local U, Th composition

Geo-Neutrino spectrum

[MeV]1.31νeCaK

[MeV]42.7ν4e4He6PbTh

[MeV]51.7ν6e 6 He8PbU

e4040

e4208232

e-4206238

Event Selection (Geo-ν)

Delayed Coincidence: 0.5 < ΔT < 1000μsec ΔR < 100 cm

0.9 < Eprompt < 2.6 MeV

1.8 < Edelayed < 2.6 MeV

Fiducial Volume:

Rprompt < 500 cm

Rdelayed < 500 cm

ρxy > 120 cmSpallation Cuts:

ΔTμ < 2 msec, total volume (for all muons)

ΔTμ < 2 sec, total volume (showering muons)

or ΔTμ < 2 sec, ΔL < 300 cm (Non-showering muons)

Efficiency U-Series : 69.2% , Th-Series : 68.0%

(α, n) Background

Recent paper shows few % lower cross section of 13C (α,n) 16O (Harissopulos et al, nucl-ex/0509014) We could reduce about B.G. uncertainty

αcomes from 210Po decay

(daughter nuclei of 222Rn)

Unfortunately, we inputted 222Rn at the construction

Expected spectrum

Accidental coincidence

BG total

(α,n) reaction

BG + Geo-ν

Reactor ν

Th-chain geo-νU-chain geo-ν

reactor

Expected + observed spectra

749.1 live days

B.G.127.4±13.3

Observed152

Signal24.2±17.9

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 the BSE model

2 90%CL

4.5 54.2

N U+ N Th :Consistent with prediction of BSE model. We observed 4.5 - 54.2 geo-neutrinos with 90%C.L99% C.L. upper limit ： 70.7 events

Th/U Mass ratio=3.9

Geo-ν after purification

749days data • error ： 54% 28% (statistical error of reactor neutrino is dominant)• Significance : 99.96% precise measurement

• fiducial volume : R < 5m 5.5m• detection efficiency : 90%

Assume 210Pb : 10-5 level

(α,n) reaction and other radioactive backgrounds are negligible

Signal v.s. heat

Fiorentini et al. (hep-ph/0508048) Re-calculation with new cross secti

on for (α,n) reaction for 13C

99% C.L. upper limit from KamLAND data

Heat (U+Th) [TW]

Sig

nal (

U+

Th)

[T

NU

]

BSE Fully radiogenic

Relationship line from geochemical and geophysical constraints

• Analysis improvement• B.G. reduction• More statistics

We will contribute to geology

Future Plan

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0.4 1.0 2.6 8.5 Visible energy 　 [MeV]

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Neutrino Astrophysics

verification of SSM

Neutrino Geophysics Neutrino Physics Neutrino Cosmology

7Be solar neutrino geo-neutrino reactor neutrino supernova relic neutrinoetc.

Next target of KamLAND

neutrino electron elastic scatteringinverse beta decay

7Be ν : neutrino electron elastic scatteringe

Very low level background is required

(We couldn’t use delayed coincidence methods)

KamLAND-II : toward solar 7Be neutrino detection

Total

210Po210Bi85Kr

7Be11C

14C 4 m radius fiducial1.2 m cylindrical cut

Required Improvements : 210Pb : 10-4~10-5

85Kr, 39Ar: ~10-6

LS PurificationDistillation System : Test Bench

• N2 gas purge (N2/LS = 25)

Rn: ~1/10Kr : ~1/100

• Distillation (110 , 37 hPa, 1time)℃

Pb: 10-4 - 10-5

Rn: (3.3 - 8.4) ×10-3

Kr : <10-5

2, 3, … , times distillation (1time : ~ 1 month)

We will achieve required performance

Purification Outline

We will start purification at next year and 7Be neutrino observation!!

The specification of the purification system was already decided. And the tender of the system was started.

After the purification…

• Solar 7Be neutrino observation with few % accuracy

• Solar 8B neutrino observation (<5MeV)

• Solar pep , CNO neutrino (with 11C tagging)

• Geo-neutrino improvements

- no backgrounds from (α,n) reaction of 13C

- accidental coincidence will be reduced

- larger fiducial volume

Summary• Rector neutrino - Rate + Shape analysis excluded no-oscillation at 99.999995% C.L. - Spectrum distortion (L/E) shows oscillatory behavior. - Oscillation parameters are precisely measured:

• Geo-neutrino - It was proven that KamLAND can detect Geo-Neutrino for the first time. - We observed 4.5 - 54.2 geo-neutrinos with 90%C.L.

• KamLAND-II - For the solar 7Be neutrino detection, purification studies have been advanced. - We will start purification at next year.

10.007.0

2256.05.0

2 40.0tan,eV 109.7

m

LS Purification and Radioactive Impurity

beforeU: ~10-10 g/g, Th: <10-12 g/g, K: 7×10-11 g/g

afterU: 3.5×10-18 g/g, Th: 5.2×10-17 g/g, K: 2.7×10-16 g/g

measurable only by KamLAND itself !

Detector Calibration Radio-Active SourceDeployment

Muon SpallationProducts

Vertex Resolution

(MeV) Ecm/6.20

Energy Resolution

E(MeV)%/ 6.2

Fiducial Volume Error: 4.7%

Detector Activity (Singles Spectrum)

Major Background Sources: LS impurity (210Pb, 85Kr, 39Ar) extrinsic gamma (40K, 208Tl) muon spallation (10C, 11C, 12B, ...)

Normal Trigger Range

Low Energy Region

Event Display : Low Energy Event

Event Display : Muon Event

Event Selection(1)Delayed Coincidence: 0.5 < ΔT < 1000μsec ΔR < 200 cm

1.8 < Edelayed < 2.6 MeV

12C captured γ

Fiducial Volume:

Rprompt < 550 cm

Rdelayed < 550 cm

Prompt Energy Window:

2.6 < Eprompt < 8.5 MeV

μ

3m

9Li

Event Selection(2)

Spallation Cuts: ΔTμ < 2 msec 　 ΔTμ < 2 sec (showering muons) 　　　　　　　　 or 　　　　 ΔTμ < 2 sec (showering muons)　　　　 ΔL 　 < 300 cm (non-showering)

Isotope Halflives Decay Mode6He 806.7ms β －

7Be 53.24day EC8Li 838ms β －

8B 170ms β －

9C 126.5ms β ＋

10C 19.25sec β ＋

11Be 13.81sec β －

11C 20.39min β ＋

9Li/8He 178.3ms/119.0msβ － + n

(α, n) Background

Recent paper shows few % lower cross section of 13C (α,n) 16O (Harissopulos et al, nucl-ex/0509014) We could reduce about B.G. estimation

Accidental Coincidence Background

⇒ 2.69 ± 0.02 events

Off - time coincidence spectrum

n + 12C*

12C + γ(4.4MeV)

16O*(6.13) → 16O + γ (6.1MeV)16O*(6.05) → 16O + e+ + e － (6.0MeV)

(α, n) Background

13C (α,n) 16O 13C (α,n) 16O*

14N (α,n) 17F15N (α,n) 18F17O (α,n) 20Ne18O (α,n) 21Ne

α

n

206Pb210Bi 210Po

210Pb

5.013 d

22.3 y

stable138.4 d

n + p → n + p (B.G for Geo neutrino)

n + 12C →

222Rn3.8 d

(5.3 MeV)

Backgrounds Summary

Correlation with Reactor Power

constrained to expected BG

4/4.22

at present statistics is not enough to state something

(α, n) Background

Energy Scale Determination

Fiducial Volume CalibrationWith Muon Spallation (12B)

Systematic Errors Summary (Reactor-ν)

Systematic Errors Summary (Geo-ν)

Systematic %

Cross section 0.2

Livetime 0.06

Fiducial volume 4.91

Trigger efficiency

(U / Th / Reactor) 0.04 / 0.09 / 0.007

Spatial Cut Efficiency 1.0

Timing Cut Efficiency 0.3

Total 5.0

Parameter Efficiency(%)Space correlation 91.32±1.49Time correlation 98.89±0.05Trigger efficiency -Delayed energy 99.98Neutron capture 99.48(I,II),99.48(III)

Total 89.82(I,II),89.83(III)

νdetection efficiency (Reactor)Space correlation Time correlation

ΔR(<2m) cut

Fiducial cut

91.32±1.49%

Capture time of spallation neutron

%05.089.98de1 s1000

s5.0

/

tt

211.2±2.6μs

MC simulationVertex resolution: 30cm/√E(MeV)

99.84%

e

Detection efficiency (Geo-ν)Neutron capture

99.5 %

Trigger U-Series: 99.96 %

Th-Series: 99.90 %

Spatial

Correlation

U-Series: 77.0 %

Th-Series: 75.7 %

Reactor: 77.3%

(α,n): 76.1%

Time correlation

90.4%

Energy of delayed event

99.97%

Spatial Correlation (MC)

MC/Data Comparison

total U-Series: 69.2%Th-Series: 68.0%

Event Selection (Geo-ν)

Delayed Coincidence: 0.5 < ΔT < 1000μsec ΔR < 100 cm

0.9 < Eprompt < 2.6 MeV

1.8 < Edelayed < 2.6 MeV

Fiducial Volume:

Rprompt < 500 cm

Rdelayed < 500 cm

ρxy > 120 cm

Spallation Cuts:

ΔTμ < 2 msec, total volume (for all muons)

ΔTμ < 2 sec, total volume (showering muons)

or ΔTμ < 2 sec, ΔL < 300 cm (Non-showering muons)

Backgrounds (Geo-ν)• Cosmic ray muon Neutron (inner of detector) negligible

Fast neutron (external) < 0.1

Spallation (9Li) 0.30±0.047

• Radioactive contamination

accidental coincidence 2.38±0.0077

spontaneous fission < 0.1

correlated fission negligible

(α, n) reaction 42.4±11.1

(γ, n) reaction negligible

• Reactor neutrino 80.4±7.2

Long lived nuclear (spent fuel rod) 1.9±0.2

total 127.4±13.3

Time variation of reactor neutrino fluxTime variation of reactor neutrino flux

Neutrino flux from distance of ~160kmdecreased.(km)L

160km

190km

Oscillation patterndepend on this variation.

/day/cm2e

Time

1 / 2

L/E Analysis χ2/ndf GOF

24.2/17 11.1%

35.8/17 0.7%

32.2/17 1.8%

spectrum shape testO

bse

rve

d / e

xpec

ted

11C Tagging

Neutrino Propagation through the Earth

Mantle or Oceanic crust?

KamLAND

Effect of the high speed region gives ~2% uncertainty of the total neutrino flux

Seismic wave velocity anomaly

Accumulation of cold slab?

Low speed (high temp.)

high speed(low temp.)

Subducting plate

Subducting plate thickness ~50km(oceanic crust ~6km)

Cold slab Oceanic crust : mantle = 1 : 9

Distance and Cumulative Flux

50% of the total flux originates within 500km.For the discussion of deep interior of the earth,we need understanding about surface geological features within ~500km

<500km

50%Crust

Sediment

Mantle

Total

Result of KamLAND and Geochemical model

• KamLAND result is consistent with prediction of BSE model.• Fully-Radiogenic (44TW) is within 99%C.L., but out of 1σ.• 99%C.L. limit is corresponding to 60 TW.

• number of events ： 28.0 (corresponding to 57.4 TNU)• 99% C.L. upper limit ： 70.7 events (corresponding to 145 TNU)• No sensitivity for U/Th ratio

Spectrum Shape Analysis

k

ThUk

dE

NNEdP 2parametersBG

2shape

),,;(log2

parametersBG

＋ 15.6－ 14.6

＋ 32.0－ 30.0

Extrinsic Gammas Screening

7Be ν: ~1μHz 40K: < 3.4μHz 208Tl: < 5.6μHz

Current KamLAND Rate

MC of extrinsic gammas (40K, 208Tl)

Solar Neutrino Prospects

11C

11C can be reduced with neutron tagging(pep and CNO neutrinos extractable???)

7Be neutrinos will be seen

between 14C and 11C background