Geo Neutrino Detection at KamLAND

F.SuekaneRCS

Tohoku University

5th Workshop on Applied Antineutrino Physics (AAP2009)

Angra dos Reis, Brazil20/03/2009

Story of this talk

* KamLAND experiment

* Geo neutrino

* Observation of geo neutrino

* Summary

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

e world

e world

Main purpose of KamLAND

is to explore the e world with;

world largest & low-background

liquid-scintillator e detector.

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

Antineutrino Energy (MeV)

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%)

05.09.19 suekane 05 Erice School 7

KamLAND Detector

Cosmicray veto

Balloon

S.S. tank

PMT

Liquid Scintillator

buffer oil

Electronics

8

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

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

shimizu

Event Display: Low Energy Event

(Enomoto WIN05)

A brief history of KamLAND

Detector Construction 1997~

Start Data Taking 01/2002

1st reactor paper (deficit) 12/2002 (PRL 90:021802,2003)

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

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

Geo neutrino paper 2005 (Nature 436:499-503,2005)

n decay 2006 (PRL96:101802-101807,2006)

LS purification for Solar 2007~

3rd reactor paper(precision) 2008(PRL 100, 221803 (2008)

Geo Neutrinos

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

Antineutrino Energy (MeV)

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%)

Nature 436, 28 July 2005

The 1st geo neutrino paper for KamLAND

shimizu

suekane 05 Erice School

ep threshold

U series:Qheat=49.7MeV

Th series:Qheat=40.4MeV

e from U/Th/K decay

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?

KamLAND datashimizu

=> Consistent with the expectation

shimizu

(17±6.2TW)

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Purification of liquid scintillator

This BKG will be gone.

Clean LSshimizu

Summary

* The geo neutrino flux is observed to be 38.9+14.4 -14.2 TNU.

This is consistent with the expectation of 36.9TNU (16TW)

and there is no surprise.

* KamLAND is purifying LS and the large 13C (a,n)16O background

will be removed.

Back up slides

Shimizu