Shigetaka MORIYAMA Kamioka Observatory, Institute for Cosmic Ray Research, The University of Tokyo 21 st Oct Korea-Japan Joint Session

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1 1. Introduction 2. Direct detection experiments in Japan 1. NEWAGE (Kyoto University) 2. NIT (Nagoya University) 3. PICO-LON (The University of Tokushima) 4. CARRACK (Kyoto University) 5. XMASS (The University of Tokyo) 3. Summary Shigetaka MORIYAMA Kamioka Observatory, Institute for Cosmic Ray Research, The University of Tokyo 21 st Oct Korea-Japan Joint Session

2 1. Introduction Dark matter is an indispensable for modern astrophysics and cosmology. It must be an unknown elementary particles, such as neutralinos of supersymmetry theories. Direct detection by nuclear recoil gives a good opportunity for experimental searches. In past, the University of Tokyo used LiF and NaF bolometers, CaF 2 scintillator, and stilbene etc. Osaka University utilized their ELEGANT detectors (NaI, CaF 2 ). ~1pb for spin dependent case. DM Nucleus

3 2. Current direct detection experiments Japan NEWAGE: Kyoto Univ. XMASS: The Univ. of Tokyo CARRACK: Kyoto Univ. NIT: Nagoya University PICO-LON: The Tokushima Univ.

4 NEWAGE (Kyoto Univ.) Kamioka lab. (New generation WIMP search with an advanced gaseous tracker experiment) latest results PLB 686(2010)11 (Miuchi et.al.) WIMP WIND F γ WIMP V0 =230 km/s SOLAR SYSTEM 220 km/s NEWAGE: Purpose WIMP-wind detection Key device Kyoto-original µ-pic detector The WIMP-wind

5 NEWAGE:First underground results The sky map (by nuclear recoil tracks) --> cosθ distribution --> upper limits 2008 run (PLB 686 (2010) 11 ) DM direction North sky by C and F nuclei ( keV) Cosθ distribution ( keV) To the future: Improve BG and threshold 1m3 size detector ~2013 to check the DAMA region direction-sensitive upper limits 10 GeV 100 GeV 1000 GeV

6 Nano Image Tracker (NIT) (Nagoya University) Concept of Directional detection by Nuclear Emulsion. WIMP wind WIMP wind WIMP Ag,Br, (C,N,O) recoil track normal emulsion(opera emulsion) NIT (Nano Imaging Tracker) 200nm size 200±16 nm density 2.8g/cc V AgBr : V gel = 3 : grains/μm size 40±9 nm density 2.8g/cc V AgBr : V gel = 3 : 7 11 grains/μm

7 Emulsion NNK008 developed at Nagoya Univ. AgBr crystal [nm] Kr ion track (400keV) 200nm Track length [nm] NNK SRIM Range threshold : 100nm Kr energy [kev] Range threshold ~100nm achieved (Ag 200keV, Br 170keV)

8 PICO-LON (The University of Tokushima) Planar Inorganic Crystal Observatory for LOw-background Neutr(al)inos To see inelastic scattering on 127 I, highly segmented detector system is planned. Propose: coincidence measurement of WIMPs Identify the type of interaction SD/SI K.Fushimi et al., Journ. of Phys. Soc. Japan 74 (2005), K.Fushimi et al., Journal of Physics Conference Series 203 (2010) NaI(Tl) 18cmX18cmX0.5cm Established! 15cmX15cmX0.1cm Under Development! SD, inelastic Scattering on 127 I 57keV 14% 60keV

9 CARRACK (Kyoto University) Rydberg atom method single microwave photon detection Matsuki and Yamamoto PL B263 (1991) 523 e g

10 XMASS experiment (The University of Tokyo)

11 The XMASS Collaboration Kamioka Observatory, ICRR, Univ. of Tokyo: Y. Suzuki, M. Nakahata, S. Moriyama, M. Yamashita, Y. Koshio, A. Takeda, K. Abe, H. Sekiya, H. Ogawa, K. Kobayashi, K. Hiraide, K. Ueshima, A. Shinozaki, H. Nishiie, S. Hirano IPMU, University of Tokyo: K. Martens, J.Liu Kobe University: Y. Takeuchi, K. Otsuka Saga University: H. Ohsumi Tokai University: K. Nishijima, D. Motoki Gifu University: S. Tasaka Waseda University: S. Suzuki Yokohama National University: S. Nakamura, I. Murayama, K. Fujii Miyagi University of Education: Y. Fukuda STEL, Nagoya University: Y. Itow, K. Masuda, H. Uchida, Y. Nishitani Seoul National University: S.B. Kim Sejong University: Y.D. Kim KRISS: Y.H. Kim, M.K. Lee, K. B. Lee, J.S. Lee

12 XMASS project XMASS Xenon MASSive detector for Solar neutrino (pp/ 7 Be) Xenon neutrino MASS detector (double beta decay) Xenon detector for Weakly Interacting MASSive Particles (DM search) It was proposed that Liquid xenon is a good candidate to satisfy scalability and low background. Y. Suzuki, hep-ph/ As a first phase, an 800kg detector for dark matter search is constructed. 10ton FV (24ton) 2.5m Solar ν, 0νββ, DM in future 100kg FV (800kg) 0.8m, DM As a first phase

13 Structure of the 800kg detector Single phase liquid Xenon (-100C, ~0.1MPa) scintillator 857kg of liquid xenon, 100kg in the fiducial volume 630 hex +12 round PMTs with 28-39% Q.E. are in LXe. photocathode > 62% inner surface Pentakis dodecahedron Interaction position reconstruction 5keVee threshold with 4.4pe/keVee Developed with Hamamatsu 1.2m diameter

14 Background reduction 1: γ/n from det. parts γ, n BG/PMT in mbq with base parts U chain / Th chain 1.5 +/ K < Co 2.9 +/ γ /n from detector parts can be reduced by: 1. Reduction of RI contamination I. PMTs: ~1/10 of prev. PMT achieved II. n contribution < 2x10-5 /kev/d/kg OFHC: brought in the mine <1month after electrorefining (Mitsubishi Material Co.) III. Material selection: >250 parts were measured by HPGe, ICPMS, Rn det. 2. Self shielding < 10-4 /kev/d/kg γ into LXe sphere Counts/day/kg/keV MC simulation kev

15 Background reduction 2: γ and n from rock γ, n γ and n from rock (α,n) will be reduced by a pure water tank γ << γ from PMT, n<<10-4 /d/kg - 11m high and 10m diameter, 72 PMTs (20 ). - First example for dark matter experiments. - Active veto for CR µ, passive for γ and n. - Applicable for future extensions. y [cm] 10 7 n s water 2m Liq. Xe n Reduction of gamma rays 2m PMT BG level 2m needed Att. vs. thickness γ >4m X [cm] (m)

16 Background reduction 3: internal radioactiv. α, β, γ Kr (Q β =687keV) and Rn can be reduced by: 1. Distillation: Kr has lower boiling point. 5 orders of magnitude reduction (0.1ppm 1ppt ) has been done with 4.7kg/hr: 10days for 1ton before filling into the detector. K. Abe et al. for XMASS collab., Astropart. Phys. 31 (2009) Filtering: by gas and liquid. Under study. LXe intake Kr GKr outlet LXe outlet Charcoal Filter GXe <30 liter-gxe/m Kr Rn LXe ~a few liter-lxe/m

17 Expected sensitivity Spin Independent σ χp >2x10-45 cm 2 for GeV WIMP, 90%C.L. 1yr exposure, 100kg FV, BG: 1x10-4 /kev/d/kg Scintillation efficiency: 0.2 Expected energy spectrum 1 year exposure σ χp =10-44 cm 2 50GeV WIMP Black:signal+BG Red:BG

18 Detector Construction

19 Construction of the PMT holder: Nov. 2009

20 PMT installation: 311 for each half, 40 for boundary

21 Cabling: 642 pairs of a coax and HV cable, each 13m length All the work is under Rn free air and clean environment.

22 Joining two halves

23 Filler attachment. Total 2.8ton: end of Feb. 2010

24 Manufacturing detector vessel A challenge: Manufacturing a large flange with soft OFHC copper. Inside: Electropolished Due to insufficient strength of its neck part, it needed to be reinforced by adding ribs. It took four months and caused a large delay.

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26 As of 18 th Oct. 2010

27 Electronics Analog Timing Modules (ATM) used for Super- Kamiokande record charge and timing of PMTs. FADCs record waveform of PMTs with 500MHz.

28 Water purification system ~5m3/hour <2mBq-Rn/m3 Rn free air generator ~20m3/hour ~a few mbq-rn/m3

29 Experimental hall, water shield, and gas handling syst. Calibration system Electronics hut Cooling tower LXe tank Distillation Tower GXe reservoir 10m3 x 2, <1MPa Shift room GXe compressor

30 Current status of commissioning run From the last Tuesday, we started to fill the detector with 1ton of LXe. It will be finished by Saturday. Contamination which absorbs scintillation light in LXe needed to be reduced. ~beginning of the next month. Detailed calibration and background reduction. ~early next year. WIMP data taking: as soon as good data quality guaranteed. ~next spring.

31 Short summary of the experiments Target SI/SD Technology Status NEWAGE Gas (CF 4 ) SD TPC Direction NIT Emulsion (Ag/Br) PICO-LON 127 I in NaI(Tl) SD Inelastic SI Emulsion Direction Segmented Scintillator CARRACK Magnetic field axions Redberg atom XMASS LXe SI/SD Liquid Xe Single phase 11.5g Running BG, Eth improving >100nm track ID succeeded R&D for 1-10kg Thin NaI(Tl) developed (15x15x0.5cm3) BG red. (1/100) needed Change atom from Rb to K 1st large scale exp. in Japan 1ton detector constructed Commissioning run started

32 Summary Current activities of direct dark matter search in Japan were presented. R&D s of direction sensitive detectors (NEWAGE and NIT) and a segmented detector (PICO-LON) are ongoing. DM axion search is (CARRACK) also being prepared. The first large scale detector in Japan (XMASS, 1ton of LXe, aiming cm 2 ) is just starting in the Kamioka mine.

33 Summary Current activities of direct dark matter search in Japan were presented. R&D s of direction sensitive detectors (NEWAGE and NIT) and a segmented detector (PICO-LON) are ongoing. DM axion search is (CARRACK) also being prepared. The first large scale detector in Japan (XMASS, 1ton of LXe, aiming cm 2 ) is just starting in the Kamioka mine in collaboration with the Korean groups.

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35 Position resolutions

36 Energy resolutions

37 Past experiments: Tokyo and Osaka group Spin independent Spin dependent 10-4 pb ELEGANT NaI World best: 4x10-8 pb 1pb ELEGANT NaI World best: 2x10-1 pb Tokyo CaF2