05.09.19suekane 05 erice school1 kamland f.suekane research center for neutrino science tohoku...

05.09.19 suekane 05 Erice School 1

KamLAND

F.SuekaneResearch Center for Neutrino Science

Tohoku University

[email protected]

Erice School 2005.9.19


KamLAND Collaboration


Contents

* Introduction to KamLAND

* Physics with e

Reactor-e

Geo-e

Solar-e

* Future prospects 7Be Solar phase 4 calibration system New Reactor

* Summary


e world e Flux at Kamioka

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

1E+7

1E+8

1E+0 1E+1 1E+2 1E+3 1E+4 1E+5

Antineutrino Energy (MeV)

Flux (/cm

2 /s/MeV)

Atmospheric ν e

Geo-νe

Reactor ν e

Solar ν e

(0.01% transition)

ν e fromPast Super Novae

Main purpose of KamLAND

is to explore the e world with;

world largest & low-background

liquid-scintillator e detector.


KamLAND Detector

Cosmicray veto

Balloon

S.S. tank

PMT

Liquid Scintillator

buffer oil

Electronics


Oil Purification system

Rn free N2 Gas Generator

Corridor to detector

Water Purification systemMonitor Displays


Key Detector Elements* Liquid Scintillator: Dodencane(80%)+PC(20%)+PPO(1.5g/L) (1150m3) Light output ~8,000photons/MeV att.>10m

* Balloon: 13m diam. 135m thick Nylon/EVOH multilayer film. Held by Kevlar mesh.

* PMT: 1325 17" aperture fast PMT (Newly developed) + 554 20" aperture (Kamiokande PMT) 34% photo-coverage

* Purification system: Water extraction + N2 bubbling U =>3.5x10-18g/g


Event Display: Cosmic-Ray Event


Event Display: Low Energy Event


Single Background

208Tl decay ~2.5/day

238U/222Rn: 3.5x10-18g/g = 20Bq232Th: 5.2x10-17g/g =100Bq40K: <2.7x10-16g/g =<0.04Bq

Reactor analysis threshold

e threshold

(cf: sea water contains10-9g/g of U.)


e detection

n+p→ d+γ 2.2MeV( )

ν e +p→ n+e+

2.2MeV~200É s

1~8MeV

t

Signal Property

e+ signal n signal

e+ +e−→ 2γ

Eν −0.8MeV( )

(ep -> e+n); an ideal reaction, because

• Only e contributes (no background from other neutrino species)• Low threshold Energy (1.8MeV)• Large cross section (~100e) • p is abundant in LS• Cross section precisely known (=0.2%)• e energy can be measured (E=Evisible+0.8MeV)• Delayed Coincidence -> powerful background rejection


ep crossection and neutron lifetime

ν ep→ e+n

e+

W −

p n

GF 2 cosθCγ μ 1− CAγ 5( )

GF 2γ μ 1− γ 5( ) ν e

n→ pe−ν e

W −

pn

GF 2 cosθCγ μ 1− CAγ 5( )

GF 2γ μ 1− γ 5( )

e−

ν e

€

p→e+n

=2π 2

I ΔM , me( )

Eν Ee

τ n

= 9.6 ×10−44 1± 0.002( )Eν Eecm2


Electron Antineutrino Event Rateat Kamioka

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

1E+3

1E+4

1E+0 1E+1 1E+2


Event rate (/year/kt//MeV)

Geo- e

Reactor e

e from Past Super Novae

Atmospheric e

KamLAND 1 /event yearsensitivity

Inverse beta decay threshold

Solar e(0.01%)

€

fν Eν( ) ×σν p→e+n

Eν( )

- KamLAND can see * Reactor Neutrino -> Neutrino Oscillation

* Geo Neutrino -> Heat Generation of Earth

* Solar e if 0.01% of e -> e

- But difficult to see * e from past SN * Atmospheric e

- If e is observed at E>9MeV, => Unknown e source


A brief history of KamLAND

Detector Construction 1997~Start Data Taking 01/20021st reactor paper (deficit) 12/2002 (PRL 90:021802,2003)

Solar e search 10/2003 (PRL 92:071301,2004)

2nd reactor paper 06/2004 (PRL 94, 081801,2005)

(spectrum distortion)Geo neutrino paper 07/2005 (Nature 436:499-503,2005)


Reactor NeutrinoElectron Antineutrino Event Rate

at Kamioka

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

1E+3

1E+4

1E+0 1E+1 1E+2



Geo- e

Reactor e


Atmospheric e



Solar e(0.01%)


Reactor Neutrino

n U235

U236*

n n

Zr94140Cs

I140

Te140

Xe140

Rb94

Sr94

Y94

e-

e-

e-

e-

e-

e-

e

e

e

e

e

e ~6 /fission & ~200MeV/fission

⇓~6×1020ν e /s/reactor

Neutrino Spectra

E~ a few MeV


ep cross section


Distance to the reactors

68GWth


If Neutrino Oscillation Exists

€

N Eν( ) = N0 Eν( ) 1−sin2 2θsin2 Δm2L4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟

=> Deficit of neutrino events

=> Distortion of energy spectrum

Thanks to the very long baseline and low reactor neutrino energy,KamLAND is sensitive with verylow m2.

Δm2 =2πEν

L~

2π ×4MeV180km

~10−5eV2

LMA region is covered!!


Event Selection

Delayed Coincidence: 0.5 < ΔT < 1000μsec ΔR < 200 cm 1.8 < Edelayed < 2.6 MeV

Fiducial Volume: Rprompt < 550 cm Rdelayed < 550 cm

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

Energy Window: 2.6 < Eprompt < 8.5 MeV

(Mar. 9, 2002 ~ Jan. 11, 2004)


€

e + p → e+ Eν − 0.8MeV( ) + n

n + p → d +γ 2.2MeV( )


Neutrino Event Spectrum

Probability of No Deficit =0.002%Probability of No Distortion=0.4%

258events

17.8events

365.2events expected

arXiv:hep-ex/0406035 v3

Background


206Pb+210Po138.4 d

Back grounds


Distortion Pattern

Oscillation back

€

Pν →ν =1−sin2 2θsin2 Δm2

4

⎛

⎝ ⎜

⎞

⎠ ⎟

LEν

⎛

⎝ ⎜

⎞

⎠ ⎟


Reactor Power Variation

Consistent withEstimated BG

No Oscillation Case


Oscillation Parameters

€

m2 = 7.9−0.5+0.6 ×10−5 eV 2 , tan2θ = 0.40−0.07

+0.10

KamLAND Only KamLAND+Solar

Solar LMA Solution

€

m2 = 7.9−0.5+0.6 ×10−5 eV 2 , tan2θ = 0.46KamLAND only:

KL+Solar:

(PRL 94, 081801,2005)


Impact of the KamLAND Result

to the Future Neutrino Physics

sin21 and m212 turn out to be not so small.

(@ oscillation maximum; )

people

Leptonic CP violation l may be accessible in the Future Experiments. Because CP asymmetry ACP can be l

arge:(Not for the case of SMA or LOW solution)

€

ACP =P ν μ → ν e( ) − P ν μ → ν e( )P ν μ → ν e( ) + P ν μ → ν e( )

≈Δm12

2

Δm132

sin2θ12

sinθ13

sinδl > 0.14sinδl


Geo NeutrinosElectron Antineutrino Event Rate

at Kamioka

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

1E+3

1E+4

1E+0 1E+1 1E+2



Geo- e

Reactor e


Atmospheric e



Solar e(0.01%)

Nature 436, 28 July 2005


ep threshold

U series:Qheat=49.7MeV

Th series:Qheat=40.4MeV

e from U/Th/K decay


U/Th abundance in the earth

　　　　　　　　　 Observations: •Chondristic Metrites (~average earth composition) contains a few 10ppb of U and Th. => ~4x1017kg of U+Th => The heat generation is ~15TW(40% of total heat dissipation)

•Earth crust contains a few ppm of U and ThMost of U,Th is concentrated in continental crust.distribution is roughly known.

Radiogenic Heat Source of EarthPhD N.R.Tolich

PhD S.Enomoto


Why Geo-Neutrinos?

Observation of Geo neutrino Abundance and Localization of U and Th Thermal Structure and History of the earth - Is the earth cooling or equilibrium state? - What is the future of the earth? - What is the residual heat of the earth formation? - What drives the geo magnetic field?


expected e energy spectrum

and event selection

€

N Eν( ) = N0 Eν( ) 1− sin2 2θsin2 Δm2L4Eν

⎛

⎝ ⎜

⎞

⎠ ⎟

€

sin2 2θ = 0.82 ± 0.07

Δm2 = 7.9−0.5+0.6 ×10−5 eV 2

⎧ ⎨ ⎩

Data sample: live time 749.1dEvent selection: Fiducial volume: R<5m T: 0.5s-500s R<1m E: 1.7-3.4 MeV (Epromt: 0.9-2.6MeV) Edelayed: 1.8-2.6MeV


Reactor 13C(,n)16O

238U232Th

Accidental

Expected total backgrounds

Expected total

Observed e candidates 152 eventsExpected total backgrounds 127±13 events

25+19-18

events

U+Th geo-Candidates: Rate only

2nd reactor results

Geo-

BSE model:19 events


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 theBSE model(19 events) Best fit: 3 U and

18 Th Geo-'s.

2 90%CL

4.5 54.2

NNUU+N+NThTh::

Consistent with predictionConsistent with prediction of geophysical model. of geophysical model. Geo-Geo- detection @95%! detection @95%!

Th/U Mass ratio=3.9

U+T < 60TW (99%CL) U+T < 60TW (99%CL) Constraint by direct method!Constraint by direct method!


e with E>9MeV

There is no known e source with flux high enough to be detected by KamLAND. If any e events are observed, it is unknown e source.

Electron Antineutrino Event Rateat Kamioka

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

1E+3

1E+4

1E+0 1E+1 1E+2



Geo- e

Reactor e


Atmospheric e



Solar e(0.01%)


Solar e

€

e = sinθν 2 + cosθν 1

ν 2decay ⏐ → ⏐ ⏐ ν 1 + X

ν 1 = cosθν e +sinθν μ

€

e

Spin−flavor precession with solar

r B ⏐ → ⏐ ⏐ ⏐ ⏐ ⏐ ν μ

flavor Oscillation ⏐ → ⏐ ⏐ ⏐ ⏐ ν e

€

Pν e →ν e∝ μ ν B

No reactor region

Two possibilities( has to be Majorana)

(1)

(2)


Event selection

0.28kt yearE=8.3MeV~14.8MeV => 0 event (1.1 +/- 0.4 BKG)

f<3.7x102/cm2/s (90%CL) <2.8x10-4 of 8B e

Reacotr


e with E>15MeVElectron Antineutrino Event Rate

at Kamioka

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

1E+3

1E+4

1E+0 1E+1 1E+2



Geo- e

Reactor e


Atmospheric e



Solar e(0.01%)

* Relic SN e

* Atmospheric e

However, too few to be detected by KamLAND

=>If KamLAND observes any e, it is unknown e source.

....... Analysis in progress.....


Flux Suppression

for LMA

pp&7Be- ~60% suppression

Y.Suzuki

But is it really so?

Future of KamLAND Solar 7Be detection


Back grounds

Total

210Po 210Bi85Kr

7Be11C

14C4 m radius fiducial1.2 m cylindrical cut

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

85Kr: ~10-6

e scattering has to be used.Decayed coincidence can not be used


LS Purification Distillation System

Test Bench

• N2 gas purge (N2/LS = 25)Rn: ~1/10Kr: ~1/100

• Fractional Distillation (164 ℃, 300 hPa)

Pb: 3×10-5

Rn: 1×10-5

Kr: < 2×10-6

Required performance is almost achieved in small system & Purification system construction is starting.

residual Pb might be organic lead(disintegrate at ~ 200℃)


4 calibration system

vertical calibration + uniformity of events3dimensional calibration Improve fiducial volume error Improve sin2212 accuracy

Installation 2005 Fall

to reduce this error


New Reactor Shika-II

L=88km (~ Oscillation Maximum)Pth=3.926GW (~15% contribution)

Increase of # of events will besmall due to oscillation=> confirmation of the measurement

http://www.rikuden.co.jp/outline2/index.html

Now20062005

test operation schedule


Summary•Reactor Neutrino Seen and m2=7.9x10-5, tan2=0.46 with KamLAND only.•Geo-neutrino Seen and consistent with earth models.

•Solar e Not seen. -> transition probability <2.8x10-4

•Preparation for solar 7Be neutrino detection in progress

•new 4 calibration system being installed.

•new reactor at ~oscillation maximum started to operation.

05.09.19suekane 05 erice school1 kamland f.suekane research center for neutrino science tohoku...

Documents

erice schoolcontentssuekane

erice school ne worldsuekane

neutrino sciencetohoku

suekaneresearch center