Antineutrino Physics in KamLANDAntineutrino Physics in KamLAND

Atsuto SuzukiAtsuto SuzukiHigh Energy Accelerator Research Organization (KEK)High Energy Accelerator Research Organization (KEK)High Energy Accelerator Research Organization (KEK)High Energy Accelerator Research Organization (KEK)

1. KamLAND Experiment

2. Reactor Antineutrino Oscillation

Study

3. Geological Antineutrino Detection

4. Conclusions

1. KamLAND Experiment

2. Reactor Antineutrino Oscillation

Study

3. Geological Antineutrino Detection

4. Conclusions

JINR Scientific Council, January 19, 2007JINR Scientific Council, January 19, 2007

KamLAND: 3KamLAND: 3rdrd Generation Experiment at Kamioka Generation Experiment at Kamioka

33rdrd generation generationKamLANDKamLAND

::1000 ton 1000 ton

Liquid Scintillator DetectorLiquid Scintillator Detector

22ndnd generation generationSuper-KamiokandeSuper-Kamiokande

::50,000 ton50,000 ton

Water Cerenkov DetectorWater Cerenkov Detector(1996 ~ )(1996 ~ )

1994: proposal1994: proposal1997: Budget was approved.1997: Budget was approved. Construction started.Construction started.1999: Japan-US collaboration1999: Japan-US collaboration2002: Data-taking started.2002: Data-taking started.

HistoryHistory

11stst generation generationKamiokandeKamiokande

::3000 ton 3000 ton

Water Cerenkov DetectorWater Cerenkov Detector(1983 - 1997)(1983 - 1997)

13 m

18 m

detector location: old Kamiokande site : 2700 m.w.e.

water Cerenkov outer detector

1000 ton liquid scintillator : 80% (dodecane) + 20% (pseudocumene) + 1.52 g/l PPO : housed in spherical plastic balloon

1325x17-inch + 554x20-inch PMT’s

photocathode coverage : 34%energy resolution : 6.2 %/(E:MeV)1/2

3000 m3 stainless steel vessel

KamLAND DetectorKamLAND Detector

: filled with a mixture of paraffin oil and dodecane ( = 0.04%)

inner view of spherical vessel

180 km

300

1. KamLAND Experiment1. KamLAND Experiment

Kamioka Liquid scintillator AntiNeutrino Detector

1000 ton liquid scintillator detector1000 ton liquid scintillator detector

77Be, CNO+pepBe, CNO+pep

KamLAND Data Samples for KamLAND Data Samples for OutcomesOutcomes

Mar. 9, 2002 – Oct. 30, 2004(live time = 749.1 days)

Mar. 4 – Oct. 6, 2002(live time = 145.4 days)

Mar. 9, 2002 – Jan. 11, 2004(live time = 515.1 days)

physics runphysics run

calibration runcalibration run

test/bad runtest/bad run

1st reactor result : Evidence for Reactor Antineutrino Disappearance

2nd reactor result : Evidence of Spectral Distortion

1st geoneutrino result : Experimental Investigation of Geologically Produced Antineutrinos

2002 2003 2004

Nuclear Power-Stations around KamiokaNuclear Power-Stations around Kamioka

Kamioka

Kashiwazaki : world biggest power

station (24.3 GW)

70 GW (~7 % of world totalpower generation)

atL ~ (175 ± 35) km

70 GW (~7 % of world totalpower generation)

atL ~ (175 ± 35) km

huge powerhuge powernearly equal distancenearly equal distance

long baseline (180 km)long baseline (180 km)

⇩⇩Kamioka :Kamioka :

suitable location forsuitable location forneutrino oscillation studyneutrino oscillation study

huge powerhuge powernearly equal distancenearly equal distance

long baseline (180 km)long baseline (180 km)

⇩⇩Kamioka :Kamioka :

suitable location forsuitable location forneutrino oscillation studyneutrino oscillation study

commercial reactors : 53 nominal power output : 152 GW

in Japan

distance from Kamioka (km)

no

. o

f n

eutr

ino

s　８６％：（１７５ ±３５）ｋｍ　９７％： Japanese stations　 2.2％： Korean　　　〃　　〃　 0.2％： European 〃　　〃　 0.12％： Taiwanese〃　　〃　 0.12 ％： North American〃

ReactorReactor e Contribution at KamiokaContribution at Kamioka

e

~210 s

How to Detect How to Detect e e in Liquid Scintillatorin Liquid Scintillator

inverse – decay :inverse – decay :

p(2.2 MeV)

n

e+

d

delayed coincidence method : delayed coincidence method : prompt eprompt e++ + delayed + delayed (2.2 MeV) (2.2 MeV)delayed coincidence method : delayed coincidence method : prompt eprompt e++ + delayed + delayed (2.2 MeV) (2.2 MeV)

ee + p + p e e++ + n + nee + p + p e e++ + n + n

E ~ Ee+ + 0.8 MeVEth = 1.8 MeV

high rejection-power for background eventshigh rejection-power for background eventshigh rejection-power for background eventshigh rejection-power for background events

prompt signal

delayed signal

2.6 MeV <Eprompt< 8.5 MeV

1.8 MeV <Edelayed< 2.6 MeV

Expect 1.5 n-Expect 1.5 n-1212CCcapturescaptures

AccidentalAccidentalbackgroundbackground

geoneutrino regiongeoneutrino region2.6 MeV

Prompt vs. Delayed EnergyPrompt vs. Delayed Energyfor for ee Candidate Events Candidate Events

expected（ no oscillation)

observed

Evidence for Reactor Evidence for Reactor ee Disappearance Disappearance

exposure 766.3 ton•yr observed ev. 258 expected ev. 365 ± 24background ev. 17.8 ± 7.3

(Nobs – NBG)/Nexpected

= 0.686 ± 0.044 (stat) ± 0.045 (syst)disappearance with 99.995 % CL

Time Dependence of Event RateTime Dependence of Event Rate

Evidence of Reactor Evidence of Reactor ee Spectral Distortion Spectral Distortion

Null Shape-DistortionNull Shape-Distortion

excluded at 99.8 % CLexcluded at 99.8 % CL

2-Flavor Oscillation Fit

2-Flavor Oscillation Fit best fit with

rate + spectrum shape

m2 (eV2) = 7.9 x 10-5

sin2 2= 0.98

un-binned likelihood fit : d.o.f. = 24.2/17

best fit withrate + spectrum shape

m2 (eV2) = 7.9 x 10-5

sin2 2= 0.98

un-binned likelihood fit : d.o.f. = 24.2/17

+0.6- 0.5

allowedallowed

LMA-II

LMA-I

LMA-0

allowedallowed

mm22 = 8.0 x 10 = 8.0 x 10-5-5 eV eV22 , sin , sin22 2 2 = 0.98 = 0.98

Constraints on Oscillation Constraints on Oscillation ParametersParameters

disfavored at 97.5% C.L.

disfavored at 98.0% C.L.

event rateevent rate spectral shapespectral shape++ee xx

excludedexcluded

LMALMA

Observation of Neutrino Oscillation PatternObservation of Neutrino Oscillation Pattern

(L(L00≡≡180 km)180 km)

evidence of evidence of neutrino oscillationneutrino oscillationat at ９９．９９． 88 ％ ％ C.L. !!!C.L. !!!

evidence of evidence of neutrino oscillationneutrino oscillationat at ９９．９９． 88 ％ ％ C.L. !!!C.L. !!!

No

bs /

Ne

xpdefinite baseline (~ 180 km) definite baseline (~ 180 km) ⇒ ⇒ test oscillation hypothesistest oscillation hypothesis

Δm2=7.9x10-5 eV2 sin22θ=0.98

L/E (km/MeV)

2-Flavor Oscillations (All Solar + KamLAND)2-Flavor Oscillations (All Solar + KamLAND)

assuming CPT invarianceassuming CPT invariance

the most precise determinationthe most precise determinationofof mm22 to dateto date

the most precise determinationthe most precise determinationofof mm22 to dateto date

m2 = 7.9 x 10-5 eV2

tan2 = 0.40

m2 = 7.9 x 10-5 eV2

tan2 = 0.40

+ 0.6– 0.5

+ 0.09– 0.07

A. Smirnov, 2002

Solutions to Solar Neutrino ProblemSolutions to Solar Neutrino Problem

KamLAND solved the solar neutrino problem KamLAND solved the solar neutrino problem under the laboratory conditions (J. Bahcall)under the laboratory conditions (J. Bahcall)

KamLAND solved the solar neutrino problem KamLAND solved the solar neutrino problem under the laboratory conditions (J. Bahcall)under the laboratory conditions (J. Bahcall)

U, Th, K decays:U, Th, K decays:radiogenic heatradiogenic heatU, Th, K decays:U, Th, K decays:radiogenic heatradiogenic heat

Experimental Investigation of Geologically Produced Antineutrinos

Experimental Investigation of Geologically Produced Antineutrinos

e

e

Heat GenerationHeat Generation::

basic factorbasic factor

Heat GenerationHeat Generation::

basic factorbasic factor

Interior DynamicsInterior DynamicsInterior DynamicsInterior Dynamics

Formation History Formation History Formation History Formation History

geoneutrino geoneutrino detectiondetection

Heat Balance between Heat Balance between Dissipation and Generation Dissipation and Generation

heat dissipationheat dissipation44 TW or 31 TW44 TW or 31 TW

mW m-2

coolingcooling ~20 TW ???~20 TW ???

radiogenic

~20 TW ???

generationgenerationnew idea : new idea : georeactorgeoreactor??????????????????

≡≡

U

U+Th

Nu

mb

er

of

anti

neu

trin

os

(1/M

eV

/de

cay

)

Antineutrino

1.8 MeV1.8 MeV

ee Energy Spectra of Energy Spectra of 238238U, U, 232232Th and Th and 4040K DecaysK Decays238U 206Pb + 8 4He + 6 e- + 6 e + 51.7 MeV

232Th 208Pb + 6 4He + 4 e- + 4 e + 42.7 MeV

40K 40Ca + e- + e + 1.31 MeV (89.3 %)40K + e- 40Ar + e + 1.51 MeV (10.7 %)

238U 206Pb + 8 4He + 6 e- + 6 e + 51.7 MeV

232Th 208Pb + 6 4He + 4 e- + 4 e + 42.7 MeV

40K 40Ca + e- + e + 1.31 MeV (89.3 %)40K + e- 40Ar + e + 1.51 MeV (10.7 %)

CoreMantle

CrustCrust

Sediment

Our Reference Earth ModelOur Reference Earth Model

[Th] /[U[Th] /[U] ~] ~ 3.93.9

outer / innerouter / inner U: 0, Th: 0U: 0, Th: 0outer / innerouter / inner U: 0, Th: 0U: 0, Th: 0

(units: ppm)(units: ppm)

continentalcontinental U: 2.8, U: 2.8, Th: 10.7Th: 10.7oceanicoceanic U: 1.7, U: 1.7, Th: 6.9Th: 6.9

continentalcontinental U: 2.8, U: 2.8, Th: 10.7Th: 10.7oceanicoceanic U: 1.7, U: 1.7, Th: 6.9Th: 6.9

upper / lowerupper / lower U: 0.012, Th: 0.048U: 0.012, Th: 0.048upper / lowerupper / lower U: 0.012, Th: 0.048U: 0.012, Th: 0.048

upper upper U: 2.8, Th: 10.7U: 2.8, Th: 10.7middlemiddle U: 1.6, Th: 6.1U: 1.6, Th: 6.1lowerlower U: 0.2, Th: 1.2 U: 0.2, Th: 1.2

upper upper U: 2.8, Th: 10.7U: 2.8, Th: 10.7middlemiddle U: 1.6, Th: 6.1U: 1.6, Th: 6.1lowerlower U: 0.2, Th: 1.2 U: 0.2, Th: 1.2

U: 0.10, Th: 0.22U: 0.10, Th: 0.22U: 0.10, Th: 0.22U: 0.10, Th: 0.22

geoneutrino production pointsgeoneutrino production pointsobserved by KamLANDobserved by KamLAND

km

km

Geoneutrino ProductionGeoneutrino Productionin Our Reference Modelin Our Reference Model

crustcrust

mantlemantle

sedimentsedimentCu

mu

lati

ve F

lux

(1/c

m2/s

ec)

cumulative geoneutrino fluxcumulative geoneutrino flux (U-chain)(U-chain)

~70%~70%

~25%~25%

<5%<5%

Antineutrino Energy (MeV)Antineutrino Energy (MeV)

Eve

nts

/0.1

7 M

eVE

ven

ts/0

.17

MeV

[U][U]++[Th][Th] = 19 ev = 19 ev

2.382.38

±0.01±0.01Accidental Accidental Coincidence Coincidence

# of # of eventseventsBackgroundBackground

127 127 ±13±13TotalTotal

best best fitfit

80.480.4

±7.2±7.2

1.9 1.9 ±0.2±0.2

Reactor Reactor ee

short livedshort lived

long livedlong lived

42 42 ±11±11

1313C (C (,n,n) ) 1616OO

Energy Distributions of Energy Distributions of Candidate & Background EventsCandidate & Background Events

signal 152

# of geoneutrinos:25 events

Maximum Likelihood Analysis Maximum Likelihood Analysis for Geoneutrino Flux for Geoneutrino Flux

# of U,Th: free parameter,# of U,Th: free parameter,mm22,sin,sin2222: best fit value: best fit value±1±1, , 1313C(C(,n),n)1616O: peak width & height: free parameterO: peak width & height: free parameter

confidence interval for # of detected geoneutrinosconfidence interval for # of detected geoneutrinos

(NU – NTh)/(NU + NTh)

NU +

NT

h

best fitbest fit

CL 68.3%CL 95.4%CL 99.7%

Th/U~3.9Th/U~3.9Th/U~3.9Th/U~3.9

reference reference modelmodel

reference reference modelmodel

First Geoneutrino ResultsFirst Geoneutrino Results

Assuming Th/U~3.9Assuming Th/U~3.9

2828

22

KamLAND observedKamLAND observedKamLAND observedKamLAND observed

total number of geoneutrinostotal number of geoneutrinos:: U+Th (best fit) : 28U+Th (best fit) : 28 U+Th (rate analysis) : 25U+Th (rate analysis) : 25

BSE predictionBSE prediction

1.45x101.45x10-31-31 ee/(target proton year)•/(target proton year)• 1.62x101.62x1077 cm cm-2-2ss-1-1 at KamLAND at KamLAND 60 TW from our reference model60 TW from our reference model

99% confidence upper limit of 99% confidence upper limit of ee flux flux::

ConclusionConclusion

KamLAND Collaboration (China-France-Japan-US)KamLAND Collaboration (China-France-Japan-US)

13C (,n) 16O* Correlated Background 13C (,n) 16O* Correlated Background

source in LSsource in LS206Pb210Bi 210Po210Pb

5.013 d22.3 y stable138.4 d

(long-lived Rn decay product)

p12C*

(4.4 MeV)

prompt

16O*

np

recoil proton+

(6.13 MeV) e+e- (6.05MeV)

prompt

n

delayed

(2.2 MeV)

13C+

17O*

( 1.1% in 12C)

recoil proton

Survived Background

Sources

Survived Background

Sources

BackgroundBackground # of # of eventsevents

99Li/Li/88HeHe 4.8 4.8 ±0.9±0.9

Accidental Accidental

CoincidenceCoincidence

2.692.69

±0.02±0.02

Fast NeutronFast Neutron

1313C (C (,n,n) ) 1616O* O*

< 0.89< 0.89

10.310.3

±7.1±7.1

TotalTotal 17.8 17.8 ±7.3±7.3

Qdeposit > 106 p.e. T < 0.5 s0.5< T< 1 ms R < 2 m

n

9Li

9Be8Be+n

:178.3 ms

9Li

background rate: 0.03 ev/daybackground rate: 0.03 ev/day

Nob

s/Nn

o osci

llat

ion

Ratio of Observed to Expected Ratio of Observed to Expected ee Flux for Reactor Neutrino Flux for Reactor Neutrino

ExperimentsExperiments

KamLANDKamLAND

LMA: LMA: mm22 = 5.5x10 = 5.5x10-5-5 eV eV22

sinsin22 2 2 = 0.833 = 0.833

LMA: LMA: mm22 = 5.5x10 = 5.5x10-5-5 eV eV22

sinsin22 2 2 = 0.833 = 0.833

neutrino tomographyneutrino tomographyFuture PlanFuture Plan

SNO+

Finland

KamLAND

e Event Selection e Event Selection

① inverse - decay selection 2.6 < Eprompt < 8.5 MeV 　 1.8 < Edelay <2.6 MeV 0.5 < T< 1000s 　　 L < 2 m 　　　　　　　　　　 no OD signals tagging efficiency 89.8%

② -induced spallation event cut T < 2 s for showering/bad

T < 2 s & L< 3m along dead-time 9.7%

③ fiducial selection

R < 5.5 m : 543.7 ton

④ data sample (2nd result): 515.1 days exposure time = 766.3 ton-year

prompt

delayed

More exotic, non-oscillations models for the antineutrinoMore exotic, non-oscillations models for the antineutrinochannel start being less favored by datachannel start being less favored by data

DecayDecay**

excluded atexcluded at95% CL95% CL

*V.Barger et al. Phys. Rev. Lett. 82 (1999) 2640

DecoherenceDecoherence††

excluded atexcluded at94% CL94% CL

†E.Lisi et al., Phys. Rev. Lett. 85 (2000) 1166

Geoneutrino Fathers and Grandfather

Geoneutrino Fathers and Grandfather

Fathers :Fathers : G. Eder, G. Eder, Terrestrial Neutrinos, Terrestrial Neutrinos, Nucl. Phys. 78, 657 (1966)Nucl. Phys. 78, 657 (1966) G.G. Marx, Geophysics by Neutrinos, Geophysics by Neutrinos,

Grandfather :Grandfather : G. Gamow, G. Gamow, Letter to F. Reines (1953) Letter to F. Reines (1953)

Czechoslovak Czechoslovak J. Phys. B19, 1471 (1969)J. Phys. B19, 1471 (1969)Czechoslovak Czechoslovak J. Phys. B19, 1471 (1969)J. Phys. B19, 1471 (1969)

Space and Time Correlations between Prompt and Delayed

Events

Space and Time Correlations between Prompt and Delayed

Events0.5<T<500 s

0<L<100 cm0.9<Eprompt <2.7 MeV

T

L

SystematicSystematic %%

Scintillator volumeScintillator volume 2.12.1

Fiducial fractionFiducial fraction 4.24.2

Energy threshold Energy threshold 2.32.3

Cuts efficiencyCuts efficiency 1.61.6

Live timeLive time 0.060.06

Reactor PReactor Pthermalthermal 2.12.1

Fuel compositionFuel composition 1.01.0

Time lagTime lag 0.010.01

Antineutrino Antineutrino spectrumspectrum 2.52.5

Antineutrino x-Antineutrino x-sectionsection 0.20.2

TotalTotal 6.56.5

Systematic ErrorsSystematic Errors(for reactor neutrino flux)

150 s <T< 10 msL < 3 m

12B

12N

12B12N

τ=29.1msQ=13.4MeV

τ=15.9msQ=17.3MeV

distribution: distribution: uniformly in spaceuniformly in space

2. Oscillation Studies by Reactor Antineutrinos2. Oscillation Studies by Reactor Antineutrinos

Reactor AntineutrinosReactor Antineutrinos

235U + n N1+ N2+ xn +6.1 + 6.1 e + (201.8±0.5 MeV)

Nuclear reactors are very intense sources of Nuclear reactors are very intense sources of ee from from the the -decays of neutron-rich fragments :-decays of neutron-rich fragments :

EEprompt prompt (e(e++) = E) = E- 0.8 MeV- 0.8 MeV

2-step signature :2-step signature :

prompt : prompt : ee++ ionization, annihilation ionization, annihilation

delayed : thermal neutron capture on delayed : thermal neutron capture on ppEEdelayed delayed (() = 2.2 MeV, ) = 2.2 MeV, t ~ 200 t ~ 200 ss

Antineutrinos are detected through inverse Antineutrinos are detected through inverse -decay : -decay :

e + p e+ + nEEthth = 1.8 MeV = 1.8 MeV

1/3 of total e’s

ννee+p→n+e+p→n+e++ cross sectioncross sectionννee+p→n+e+p→n+e++

cross sectioncross section

Ev (MeV)

13C( , n) 16O*

(n, p) 12C(n, n) 12C

13C( , n) 16O

Expected Energy Expected Energy Spectra of 13C (,n) 16O*, 16O Correlated Events

Expected Energy Expected Energy Spectra of 13C (,n) 16O*, 16O Correlated Events

free parameter in likelihood analysis free parameter in likelihood analysis peak height for reactor neutrinospeak height for reactor neutrinos peak height & width for geoneutrinos peak height & width for geoneutrinos

reactorreactorgeo-geo-

expected (no oscillation)

observed

Time Dependence of Observed Event Rate

Time Dependence of Observed Event Rate

90% CL

···· ···· best fitbest fit

fit constrained through

expected background

(0.03 events/day)(0.03 events/day)

More DataMore Data

Crustal thicknessCrustal thickness

Sediment thicknessSediment thickness

longitude (deg.)

lati

tud

e (d

eg.)

U/Th in Japan and near KamiokaU/Th in Japan and near Kamioka

Background Level in KamLAND-IIBackground Level in KamLAND-II

14,11,10C : major background sources

KamLAND-IIKamLAND-IIKamLAND-IIKamLAND-II

Expected Energy Spectrum of Single Events in KamLAND-II

Expected Energy Spectrum of Single Events in KamLAND-II

1111CCCNOCNOpeppep

7Be7Be

3 years data3 years data