KamLAND: Measuring Neutrino-Oscillation with...

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KamLAND: Measuring Neutrino-Oscillation with Reactors Patrick Decowski UC Berkeley UCSC November 15, 2004

Transcript of KamLAND: Measuring Neutrino-Oscillation with...

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KamLAND: Measuring Neutrino-Oscillation with

Reactors

Patrick DecowskiUC Berkeley

UCSC November 15, 2004

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Patrick Decowski / UC Berkeley

L

Reactor Experiments

νe

νe

νx

νe

Few MeV anti-neutrinos, energy too low to produce μ or τ➡ disappearance experiments

?

?

P (νe → νe) = 1 − sin2 2θ sin21.27∆m2L

E

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• Many different experiments

• Baselines up to 1km

• No evidence for disappearanceνe

Oscillation searches with Reactors

Reactors have played an important role in the early history of neutrinos and in neutrino-oscillation searches: 1953 - Present

Poltergeist(Reines & Cowan 1955)

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Nobs/

Nex

p

101

102

103

104

105

Distance to Reactor (m)

ILL Savannah River Bugey Rovno Goesgen Krasnoyarsk Palo Verde Chooz

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Reactor Anti-Neutrinos

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Reactor Neutrinos

235U fission

The stable products most likelyfrom Uranium fission:

Together 98 protons and 136 neutrons

235

92 U + n → X1 + X2 + 2n

9440Zr

14058 Ce

6 neutrons have to -decay to reach stable matter, producing 6 / fissionνe

94 140

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Calculating Neutrino Spectra

• Fission rates provided by reactor companies

• Chiefly function of thermal power

• Weak function of inlet T: 10% -> ~0.15% rate change

10-5

10-4

10-3

10-2

10-1

1

0 1 2 3 4 5 6 7 8 9 10

Energy (MeV)

ne

utr

ino

s/M

eV

/fis

sio

n

238U

239Pu

235U

241Pumeasured at ILL

K.Schreckenbach et al., Phys.Lett.B160(1985)325

A.A.Hahn et al., Phys.Lett.B218(1989)365

theoretical 744 tracesP.Vogel et al., Phys. Rev. C24(1981)1543

Date

3/3 1/30

fis

sio

n/s

)1

9F

iss

ion

ra

te (

10

0

1

2

3

4

5

6

7

819

x10

Mar Apr May Jun

2002Jul Aug Sep Oct Nov Dec Jan Feb Mar

2003Apr May Jun Jul Aug Sep Oct Nov Dec

A typical 1.3GWe class BWR in Japan

0

1

2

3

4

5

6

7

8

U235

U238Pu239

Pu241

Data provided according to the special agreement betweenTohoku Univ. and a Japanese nuclear power reactor operator.

Only 4 isotopes relevant

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Detected Reactor Spectrum

1.8MeV threshold in Inverse Beta Decay

In practice, only 1.5 neutrinos/fission detectable

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• Reactors produce:

• Only anti-neutrinos

• On average around 6 per fission

• Reactor anti-neutrino spectra measured at short baseline

• Gösgen (1986)

• Bugey (1996)

• Chooz (1999)

• Palo Verde (2001)

Reactor Spectra

Gösgen

νe

Agreement of measured with expected~2% - no near detector necessary!

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Distortion of Spectrum

Neutrino oscillation changes both the overall normalization and the shape of the spectrum

P (νe → νe) = 1 − sin2 2θ sin21.27∆m2L

E

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Anti-neutrino Detection Method

Reaction process: Inverse beta decay

νe + p → e+

+ n

n + p → d + γ

e n

e+

2.2MeV

Scintillatorγ γ

γ

Scintillator is both target and detector

• Distinct two step process:

• prompt event: positron

• delayed event: neutron capture after ~210μs• 2.2 MeV gamma

Delayed coincidence: good background rejection

Eνe! Eprompt + 0.8MeV

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Long Baseline Means Large Detectors

1m

PoltergeistChooz4 m

KamLAND20 m

Log 1

0(M

uon

Flux

) (m

-2s-

1 )Depth (mwe)

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The KamLAND Experiment

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from 53 Reactor Cores in Japan

~95.5% from Japan~3.5% from Korea

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

Effective distance ~180km

∼ 6 × 106/cm2/secReactor neutrino flux,

358 m36◦25′35.562′′

137◦18′43.495′′long.lat.alt.

1000m rock= 2700 mwe

νe

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KamLAND Collaboration

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Building KamLAND

1998

September 2001 January 2002

Data Taking

September 2000

October 1999

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KamLAND detector

• 1 kton Scintillation Detector

• 6.5m radius balloon filled with:

• 20% Pseudocumene (scint)

• 80% Dodecane (oil)

• 34% PMT coverage

• ~1300 17” fast PMTs

• ~550 20” large PMTs

• Multi-hit, deadtime-less electronics

• Water Cherenkov veto counter

Water Cherenkov Outer Detector

Buffer Oil1800 m3

20m

3200 m3

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0.4 1.0 2.6 8.5 Visible energy [MeV]

Neutrino Astrophysicsverification of SSM

Neutrino Geophysicsverification of earth

heat model

Neutrino PhysicsPrecision measurement of oscillation parameters

Neutrino Cosmologyverification of

universe evolution

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

1st reactor result PRL 90, 021802 (2003)2nd reactor result hep-ex/0406035

Solar PRL 92, 071301 (2004)

ν̄e“soon”future2nd phase

neutrino electron elastic scatteringinverse beta decayν + e− → ν + e− ν̄e + p → e+ + n

KamLAND Physics Capabilities

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Detector Performance

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Trigger Efficiency

0.9MeVPrompt Trigger:200 PMT hits (~0.7MeV)

Delayed Trigger:120 hits for 1msec after prompt trigger

Reactor analysis threshold: 2.6MeV, trigger is 100% efficient

(To study radioactive backgrounds)

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0

500

1000

1500

2000

2500

visible energy (MeV)4 6 8 10 12 14 16

12

B/12

N

0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5

68

Ge65

Zn

n-p n-12

C

60

Co

visible energy (MeV)

0 1 2 3 4 5 6 7 8 9

-0.04

-0.02

0

0.02

0.04

Energy (MeV)

E/E

-ray sourcesγ decayβ

Ge68

Co

60

Zn65

n-p

C12n-

N12

B/12

Energy scale error at 2.6 MeVCherenkov/BirksTime dependencePosition dependence20” PMT non-linearityTotal

1.0%1.3%1.0%0.8%2.0%

σ

E∼ 6.2%√

EEnergy Resolution:

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0 5 10 15 20 25 30 35 40 45 50-8

-6

-4

-2

0

2

4

6

8prompt

)2

(m2

+y2x

z (m

)

0 5 10 15 20 25 30 35 40 45 50-8

-6

-4

-2

0

2

4

6

8delayed

)2

(m2

+y2x

z (m

)

Inverse beta-decay selection:

● Rprompt, delayed < 5.5 m

● ΔR < 2 m

● 0.5 μs < ΔT < 1000 μs● 1.8 MeV < Edelayed < 2.6 MeV

● 2.6 MeV < Eprompt < 8.5 MeV

• Muon-induced spallation event cuts:● 2 ms veto after every μ● 2 s veto for showering/bad μ● 2 s veto in a R = 3m tube along track

Tagging efficiency 89.8%

Dead time 9.7%Balloon

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02 03 04 05 06 07 08 09 10 1112 01 02 03 04 05 06 07 08 09 10 1112 01

ho

ur

0

2

4

6

8

10

12

14

16

18

20

22

24

2002 2003 2004

Liv

eT

ime

[d

ay

]

0

100

200

300

400

500

600

Physics Run Calibration Run (source,laser and LED)

Test/Bad Run

1st result4 Mar 2002 - 6 Oct 2002

145.1 days

2nd result9 Mar 2002 - 11 Jan 2004

515.1 days

X 3.55 live time

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Quite a few Reactors were Off

Jul/02 Jan/03 Jul/03 Jan/04

(ev

ents

/day

)no-o

scil

exp

N

0

0.2

0.4

0.6

0.8

1

1.2

Wei

gh

ted

dis

tan

ce(k

m)

150

160

170

180

190

200

210

no-oscil

expN

Weighted distance

Period for first result

In 2002 it was discovered that some of the Japanese reactor companies had falsified safety records

Anti-neutrino flux was 20% lower

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Backgrounds

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Accidental Backgrounds

0.0086 ± 0.000051st result (5m fiducial 162 ton-yr)

2.69 ± 0.022nd results (5.5m fiducial 766.3 ton-yr)

prompt energy [MeV]

0 1 2 3 4 5 6 7 8 9 10

co

un

ts/2

0k

eV

10-1

1

10

102

103

104

105

106

208Tl from wall

210Bi in LS

analysis threshold

Fiducial volume is limited by accidental backgrounds.

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energy [MeV]0 2 4 6 8 10 12 14

co

un

ts/b

in

0

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

9LiT1/2 = 0.18 sec

9Be8Be + n

β ntotal 50%

4.8 ± 0.9 events (E > 2.6 MeV)(2nd result)

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Dealing with muons

0 to 2 ms after muon outside scint: veto entire volume.

>2 ms after muon outside scint:all of fiducial volume is okay.

0 to 2 ms after muon in scint: veto entire volume

2 ms to 2 s after muon in scint: veto events within 3 m of track

0 to 2 ms after shower in scint: veto entire volume

2 ms to 2 s after shower in scint: also veto entire volume

3 Typical scenarios of muons interacting in KamLAND

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with Radioactive Sourceswith Muon Spallation

z-axis[cm]-600 -400 -200 0 200 400 600

z d

ev

iati

on

[cm

]

-10

-5

0

5

10Co

Zn

GeAm/Be(4.4MeV)

Am/Be(~7.6MeV)

0 0.2 0.4 0.6 0.8 1 1.2 1.40

500

1000

1500

2000

2500

3000

3500

4000

fiducial

balloonradius

3(R/6.5m)

Events/Bin

0 0.2 0.4 0.6 0.8 1 1.2 1.40

200

400

600

800

1000

fiducial

balloonradius

3(R/6.5m)

3(delayed R/6.5m)0 0.2 0.4 0.6 0.8 1 1.2p

rom

pt

R -

del

ayed

R [

cm]

-150

-100

-50

0

50

100

150

Li (prompt energy>4MeV)9He8

fiducial

12B

delayed coincidence

Fiducial/Total Volume Ratios

Geometrical

12Bp(n, γ)d

0.595 ± 0.013

0.607 ± 0.006 ± 0.006

0.587 ± 0.0139Li relative < 2.7%

Fiducial Volume uncertainty 4.7%

p(n, γ)d

9Li

(=

696.9 m3

1171 ± 25 m3

)

β + n

Fiducial Volume Uncertainty

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Fast neutron

OD miss-taggingrock penetrating

Total

<0.4<0.5<0.9

recoil proton+

neutron capture

sec]µ T [∆500 1000 1500 2000

0

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

0

10

20

30

40

50

60

70

prompt radius [cm]

0 100 200 300 400 500 600 700 800

0

10

20

30

40

50

5m 5.5m

prompt energy [MeV]0 2 4 6 8 10 12 14

0

5

10

15

20

25

30

35

40

fiducial

Tagged eventsR-distribution prompt energy time difference delayed energy

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(α,n) Background

222Rn (3.8d)218Po214Pb

214Bi214Po210Pb (22.3y)

210Bi (5.013d)

210Po (138.4d)206Pb (stable)

equilibrium

(Eα = 5.3MeV )

10.6 events (E>2.6MeV)

1.1% abundance (measured)

13C(α,n)16O ∼ 10−7

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

Visible Energy (MeV)

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Ev

en

ts/M

eV

/se

c

10-4

10-3

10-2

10-11

10

102

103

104

85Kr210Po

210Bi

Low energy spectrum

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Uncertainty %Fiducial volume 4.7

Energy threshold 2.3Cuts efficiency 1.6

Live time 0.1Reactor thermal power 2.1

Fuel composition 1.0Antineutrino spectra 2.5

Cross section 0.2Total uncertainty 6.5

Systematic Uncertainties

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Results

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1st Reactor Result

Data Summaryfrom March 4 to October 6, 2002

145.1 live days, 162 ton-year exposure

Analysis threshold 2.6 MeVexpected signal

BGobserved

86.8 ± 5.6

54Neutrino disappearance at 99.95% CL.

R = 0.611 ± 0.085(stat) ± 0.041(syst)

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

1 ± 1

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Nob

s/N

no_osc

illa

tion

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

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Before KamLAND: After KamLAND 1st result:

RSFPFCNCdecay

decoherenceetc.

tan2(!)

"m

2 in

eV

2

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 10 102

Ga

Cl

SuperK

SNO

LMA

SMA

LOW

VAC

LMA

SMA

LOW

RSFPFCNCdecay

decoherenceetc.

VAC

KamLAND reactor disappearance excluded all but LMA solution

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Data Summaryfrom 9 Mar 2002 to 11 Jan 2004

515.1 live days, 766.3 ton-year exposure

expected signalBG

observed

Neutrino disappearance at 99.998% CL.

KamLAND collaboration, hep-ex/0406035

365.2 ± 23.7

258

for Mar to Oct 2002is consistent with first results

2nd resultData Summaryfrom March 4 to October 6, 2002

145.1 live days, 162 ton-year exposure

expected signalBG

observed

86.8 ± 5.6

54Neutrino 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

×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(stat) ± 0.042(syst)

Caveat: ratio does not have an absolute meaning in KamLAND, since, with oscillations, it depends on which reactors are on/off

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Delayed Coincidence

(M

eV)

del

ayed

E 2

3

4

5

(MeV)prompt

E0 1 2 3 4 5 6 7 8

0

12C(n, γ) expected1.5

accidental

1.8 < Edelayed < 2.6 MeV

2.6 < Eprompt < 8.5 MeV

Clear delayed coincidence events

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A fit to a simple rescaled reactor spectrumis excluded at 99.6% CL

Energy Spectrum

Best-fit oscillation:

∆m2

= 7.9+0.6−0.5 × 10

−5eV

2

tan2θ = 0.46

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Unbinned Likelihood: 2 nu Oscillation

∆m2

= 7.9+0.6−0.5 × 10

−5eV

2

LMA2 is excluded at 98.0%

LMA0 is excluded at 97.5%

tan2θ = 0.46

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Global Analysis

Solar Experiments are sensitive to

tan2θ = 0.40

+0.10−0.07

∆m2

= 7.9+0.6−0.5 × 10

−5eV

2

Most precise to date!

θ

∆m2KamLAND is most sensitive to

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No

Osc

illatio

n

Current statistics not enough to make firm statements

Correlation with Reactor Power

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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

Ele

ctr

ic p

ow

er

flu

x (

10

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

-1010!

Electric power flux at KamLAND

0

1

2

3

4

5

6

7

8

9

10

JAIF data

2002.

2003.

2004.

2nd result

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Patrick Decowski / UC Berkeley

Ratio of measured to expected spectrum

Oscillation pattern for one of a given energy

νe

Best-fit oscillation accounting for energy spectrum and reactor distribution

Pee = 1 − sin2 2θ sin2(∆m2

4

L

E)

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Patrick Decowski / UC Berkeley

V.D.Bager et al.,PRL82,2640(1999)

E.Lisi et al.,PRL85,1166(2000)

oscillation Pee = 1 − sin2 2θ sin2(∆m2

4L

E)

decay Pee = (cos2 θ + sin2 θ exp(−m2

L

E))2

decoherence Pee = 1 − 12

sin2 2θ(1 − exp(−γL

E))

Page 44: KamLAND: Measuring Neutrino-Oscillation with Reactorsscipp.ucsc.edu/seminars/experimental/files/seminar_041115/Decows… · Patrick Decowski / UC Berkeley • Many different experiments

Future activities at KamLAND

Page 45: KamLAND: Measuring Neutrino-Oscillation with Reactorsscipp.ucsc.edu/seminars/experimental/files/seminar_041115/Decows… · Patrick Decowski / UC Berkeley • Many different experiments

Patrick Decowski / UC Berkeley

Karsten Heeger, LBNL Sendai, September 20, 2003

Development and Testing of an Off-Axis

Calibration System for KamLAND

KamLAND 4! GroupLawrence Berkeley National Laboratory

It’s being built!z-axis calibration

full volume calibration

Future Improvements

Reduce Fiducial Volume and Energy Uncertainty

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

KamLAND onlyrate+shape sensitivity

(rough estimation)

capability to reject full mixing

mixing angle determination comparable with current solar data

fact

or ~

2 im

prov

emen

t?

Page 47: KamLAND: Measuring Neutrino-Oscillation with Reactorsscipp.ucsc.edu/seminars/experimental/files/seminar_041115/Decows… · Patrick Decowski / UC Berkeley • Many different experiments

Patrick Decowski / UC Berkeley

What is the Earth’s heat source?

0.0

20.0

50.0

80.0

110.0

mW/m2Surface Heatflux at 2x2 degrees

Surface heat flux measurement

Total flow of 44 TWis 40 times larger than total world reactor power.

Combining all the available geo-chemical knowledge:

Radioactivity 20 TWUranium 8TW, Thorium 8TW,

Potassium 4TW

U,Th are condensed in the

crust

Page 48: KamLAND: Measuring Neutrino-Oscillation with Reactorsscipp.ucsc.edu/seminars/experimental/files/seminar_041115/Decows… · Patrick Decowski / UC Berkeley • Many different experiments

Patrick Decowski / UC Berkeley

Neutrinos from radioactivity provide direct information on the earth’s interior

Uranium seriesThorium series

Analyzing data E< 2.6MeVanalysis forthcoming

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Patrick Decowski / UC Berkeley

Verification of the SSM with more abundant neutrinos is important.

Real time measurement of low energy solar neutrinos has never been done.

KamLAND

Real time measurements

(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

Towards 7Be Solar Neutrino Observation

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Patrick Decowski / UC Berkeley

Detecting Solar Neutrinos

0

500

1000

1500

2000

2500

3000

0 200 400 600 800 1000

cou

nts

/25

keV

Energy [keV]

KamLAND future goal

14C

(assume 14

C/12

C=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)

Detecting through elastic scattering:

Challenging experiment: Reducing backgrounds is crucial!

νeνe

e- e-

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1104∼5

110∼6

requiredfurther improvement

For future physics

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

4

Visible Energy (MeV)

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Ev

en

ts/M

eV

/se

c

10-4

10-3

10-2

10-11

10

102

103

104

Current background level

7Be νpp ν

14C

11C

85Kr210Bi210Po

daughter of 210Pb

SSM

Page 52: KamLAND: Measuring Neutrino-Oscillation with Reactorsscipp.ucsc.edu/seminars/experimental/files/seminar_041115/Decows… · Patrick Decowski / UC Berkeley • Many different experiments

Patrick Decowski / UC Berkeley

• KamLAND’s updated results strengthen support for “neutrino disappearance”

• Best-fit KamLAND+Solar oscillation parameters are:

• No-oscillation hypothesis rejected at 99.6%

• Other disappearance mechanisms strongly disfavored

• Neutrino oscillation observed in:

• solar, atmospheric, accelerator and reactor experiments

• Look out for many other things to come out of KamLAND!

Summary

∆m2

= 7.9+0.6−0.5 × 10

−5eV

2tan

2θ = 0.40

+0.10−0.07 Best to date!