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

suekane@awa.tohoku.ac.jp

Erice School 2005.9.19

KamLAND Collaboration

Contents

* Introduction to KamLAND

* Physics with e

Reactor-e

Solar-e

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

* Summary

e world e Flux at Kamioka

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

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

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

GF 2 cosθCγ μ 1− CAγ 5( )

GF 2γ μ 1− γ 5( ) ν e

n→ pe−ν e

GF 2 cosθCγ μ 1− CAγ 5( )

GF 2γ μ 1− γ 5( )

p→e+n

=2π 2

I ΔM , me( )

Eν Ee

= 9.6 ×10−44 1± 0.002( )Eν Eecm2

Electron Antineutrino Event Rateat Kamioka

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+0 1E+1 1E+2

Geo- e

Reactor e

Atmospheric e

Solar e(0.01%)

Reactor Neutrino

n U235

Zr94140Cs

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

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

⎝ ⎜

⎠ ⎟

⎝ ⎜

⎠ ⎟

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

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

Δm132

sin2θ12

sinθ13

sinδl > 0.14sinδl

Geo NeutrinosElectron Antineutrino Event Rate

at Kamioka

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

BSE model:19 events

Rate + Shape analysisC.L. contours for detected U and Th geo-s.

(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+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

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)

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+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

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...

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