Kam LAND double beta decay 136 experiment using

Kam. LAND double beta decay 136 experiment using Xe ( Kam. LAND-Zen ) Masayuki Koga @ RCNS Tohoku University Contents: Ø summary of Kam. LAND Ø Kam. LAND-Zen experiment Masayuki Koga ICHEP 2010 1

１０００ｍ Masayuki Koga ICHEP 2010 2

Summary of Kam. LAND Ø Ø Ø 1998 -2001: construction 2002: data-taking start We got some results ・　reactor anti-neutrino observation neutrino deficit at ~175 km base spectral distortion precise oscillation parameters measurement ・　Geo neutrino detection Ø 2009~: Kam. LAND is running for 7 Be solar neutrino observation after the LS distillation Ø 2011~: Xe phase Masayuki Koga ICHEP 2010 3

Reactor Anti-Neutrino LMA 2 Masayuki Koga ICHEP 2010 4

Geo Neutrino observation Radio active nuclei produce heat 238 U -> 206 Pb + 84 He + 6 e- + 6νe+ 51. 7 Me. V 232 Th -> 208 Pb + 64 He + 4 e- + 4ν + 42. 7 Me. V e 40 K -> 40 Ca + e- + ν + 1. 31 Me. V e Terrestrial heat flow 31~44 TW Contribution of radioactive nuclei ~20 TW ( U series 8 TW / Th series 8 TW / 40 K 4 TW ) from Crust + Mantle -- based on Chondrite model (BSE model) Upper crust of land U: 2. 8 ppm / Th: 10. 7 ppm Rudnick et al (1995) No radiogenic heat from the core Th/U ratio ~3. 7 Masayuki Koga ICHEP 2010 5

Geo Neutrino observation Ø preliminary result (K. Inoue, Neutrino 2010) Masayuki Koga ICHEP 2010 6

Rate-Shape-time analysis 0 signal is rejected at 99. 997%CL. (>4σ) 　　　　　　(rate-shape-time Δχ２） # of geo-ν events corresponds to 16 TW (for U+Th) Consistent with the model prediction Masayuki Koga ICHEP 2010 7

7 Be neutrino observation LS was purified by the distillation system (2007 and 2008) Installed new electronics – for 13 C(α, n) background reduction (on going) Data-taking continue (to March 2011) Masayuki Koga ICHEP 2010 8

Kam. LAND Zen experiment (Kam. LAND zero neutrino Double Beta decay) RCNS Tohoku University K. Inoue J. Shirai T. Mitsui M. Koga K. Nakamura Y. Kishimoto S. Yoshida Y. Gando H. Ikeda I. Shimizu Y. Minekawa Y. Takemoto A. Terashima H. Watanabe H. Takahashi T. Morikawa H. Yabumoto H. Yoshida N. Takahashi B. Xu E. Chatwin-Davies Y. Ohno R. Kato T. Nakata KEK A. Suzuki IPMU Tokyo Universisty A. Kozlov University of Tennessee Y. Efremenko Colorado State university B. E, Berger, D. Warner 禅 TUNL W. Tornow, D. Markoff, H. Karwowski Masayuki Koga ICHEP 2010 9

Advantage for ββ　experiment on Kam. LAND has huge volume: 1, 200 m 3 Liquid Scintillator Ultra low radioactivity Low threshold : ( It will be Eth= few 100 ke. V) established distillation technique experience of balloon development new electronics (from 2009) mach advantage for 0νββ　experiment ! Ø Disadvantage Current Energy Resolution: (34% photo coverage) Ø This is enough on earlier stage ! Masayuki Koga ICHEP 2010 10

Kam. LAND-Zen project Merit of using 136 Xe on Kam. LAND Nucleas T 0ν 1/2(50 me. V) T 2ν 1/2 measured (year) Nat. Abundane （％） Q-value （ke. V） 136 Xe→ 136 Ba 4. 55× 1026 >1022 8. 9 2476 Rodin et al. , Nucl. Phys. A 793 (2007)213 -215 Available the Isotopic enrichment (>90%) Ø purification method was established Ø solubility to LS > 3%, easy extracted Ø slow 2νββ (T 2ν 1/2 >1022 years) small T 0ν/ T 2ν　ratio Ø * basic idea by R. S. Raghavan Phys. Rev. Lett. 72 (1994) Masayuki Koga ICHEP 2010 11

Kam. LAND-Zen project 1 st phase enriched Xe 400 kg 　R=1. 7 m balloon 　V=20. 5 m 3, S=36. 3 m 2 LS : C 10 H 22(81. 8%)+PC(18%) 　　　+PPO+Xe(~2. 5 wt%) ρLS：　0. 78 kg／ℓ high sensitivity with low cost 3. 4 mφ balloon 4. 6 mφbaloon tank opening (2013 or 2015) 2 nd phase enriched Xe 1000 kg Brighter LS Winstone corn mirror Masayuki Koga ICHEP 2010 R=2. 3 m balloon 　V=51. 3 m 3, S=66. 7 m 2 improvement of energy resolution (brighter LS, higher light concentrator ) 12

Developments of system for 400 kg Xe phase 1. Xe gas loading/ extraction system 3. Enriched Xe • We have 190 kg 90% enriched Xe gas • Purchase 210 kg more to March 2011 (400 kg total) 4. Mini Balloon Φ 3. 4 m System will be ready in December 2010 2. New electronics - MOGURA Handling and pressurized test by water (80μm film, June 2010) More R&D • ultra low contamination films U/Th/40 K ~ 10 -13 g/g • more thin film ~25μm For BG reduction using tagging. Masayuki ICHEP 2010 Installed in. Koga 2009. MIB will be delivered to March 2011 13

Background study using Kam. LAND MC (GEANT 4) Major BG (1). 136 Xe 2νββ (2). spallation isotopes : 10 C, 11 Be => 1/10 using new electronics help (3). 8 B solar neutrinos <4. 9 events/d/kton on Kam. LAND (4). from Mini Balloon (MIB) material : 208 Tl, 214 Bi => vertex cut, Simulated Energy Spectrum at Kam. LAND Assumed - 400 kg 90% enriched Xe loaded LS - MIB contamination (238 U, 232 Th, 40 K) = (10 -12, 10 -11)[g/g] - neutrino effective mass <mν> = 150 me. V (the lower limit of the current claimed detection) - T 1/2(2νββ) > 1022 y - T 1/2(0νββ) > 1. 14 x 1024 y - 10 C 90% tag, 214 Bi 66% tag Summary of BG and signal in signal region [events/year] Masayuki Koga ICHEP 2010 14

Target sensitivity of the 400 kg phase is ~60 me. V 2 years on 100% fiducial vol. @90% enrichment Masayuki Koga ICHEP 2010 15

summary Ø Ø Ø Kam. LAND is running for reactor, Geo, 7 Be solar (to 2011) Kam. LAND have ability to do 0νββ　experiment Kam. LAND-Zen project will start useing 400 kg 90% enriched Xe from May 2011 Target sensitivity on 400 kg Phase ~60 me. V @2 years Planning Xe 1000 phase (from 2013 or 2015: depend on funding) Thank you! Masayuki Koga ICHEP 2010 16