Geo Neutrino Detection at Kam LAND F Suekane

Geo Neutrino Detection at Kam. LAND F. Suekane RC S Tohoku University 5 th Workshop on Applied Antineutrino Physics (AAP 2009) Angra dos Reis, Brazil 20/03/2009

Story of this talk * Kam. LAND experiment * Geo neutrino * Observation of geo neutrino * Summary

ne world

ne world Main purpose of Kam. LAND is to explore the ne world with; world largest & low-background liquid-scintillator ne detector.

PMT Kam. LAND Detector Electronics Liquid Scintillator buffer oil Balloon S. S. tank 05. 09. 19 suekane 05 Erice School 7 Cosmicray veto

Water Purification system Monitor Displays Rn free N 2 Gas Generator Corridor to detector Oil Purification system 8

Key Detector Elements * Liquid Scintillator: Dodencane(80%)+PC(20%)+PPO(1. 5 g/L) (1150 m 3) Light output >8, 000 photons/Me. V latt. >10 m * Balloon: * PMT: 13 m diam. 135 mm thick Nylon/EVOH multilayer film. Held by Kevlar mesh. 1325 17" aperture fast PMT (Newly developed) + 554 20" aperture (Kamiokande PMT) 34% photo-coverage * Purification system: Water extraction + N 2 bubbling U =>3. 5 x 10 -18 g/g

ne detection (nep -> e+n); an ideal reaction, because • Only ne contributes (no background from other neutrino species) • Low threshold Energy (1. 8 Me. V) • Large cross section (~100 sne) • p is abundant in LS • Cross section precisely known (ds=0. 2%) • ne energy can be measured (En=Evisible+0. 8 Me. V) • Delayed Coincidence -> powerful background rejection

shimizu

(Enomoto WIN 05) Event Display: Low Energy Event

A brief history of Kam. LAND Detector Construction 1997~ Start Data Taking 01/2002 1 st reactor paper (deficit) 12/2002 Solar ne search 2003 (PRL 92: 071301, 2004) 2 nd reactor paper(spectrum) 2004 (PRL 94, 081801, 2005) Geo neutrino paper 2005 (Nature 436: 499 -503, 2005) n decay 2006 (PRL 96: 101802 -101807, 2006) LS purification for Solar n 2007~ 3 rd reactor paper(precision) 2008(PRL 100, 221803 (2008) (PRL 90: 021802, 2003)

Geo Neutrinos Nature 436, 28 July 2005

The 1 st geo neutrino paper for Kam. LAND

shimizu

ne from U/Th/K decay U series: Th series: Qheat=49. 7 Me. V Qheat=40. 4 Me. V nep threshold suekane 05 Erice School

Why Geo-Neutrinos? Observation of Geo neutrino ÞAbundance and Localization of U and Th Þ 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?

Kam. LAND data shimizu

shimizu (17± 6. 2 TW) => Consistent with the expectation

shimizu

Purification of liquid scintillator Clean LS This BKG will be gone. shimizu

Summary * The geo neutrino flux is observed to be 38. 9+14. 4 -14. 2 TNU. This is consistent with the expectation of 36. 9 TNU (16 TW) and there is no surprise. * Kam. LAND is purifying LS and the large 13 C (a, n)16 O background will be removed.

Back up slides

Shimizu