XMASS

XMASS20113720111

ContentsIntroduction

The XMASS detector

Current status of XMASS2Introduction3 XMASS experiment

Dark matterDouble betaSolar neutrino Xenon detector for Weakly Interacting MASSive Particles (DM search) Xenon MASSive detector for solar neutrino (pp/7Be) Xenon neutrino MASS detector (bb decay)What is XMASS?Multi purpose low-background and low-energy threshold experiment with liquid Xenon4

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XMASS Collaboration5Kamioka Observatory, ICRR, Univ. of TokyoY. Suzuki, M. Nakahata, S. Moriyama, Y. Kishimoto, M. Yamashita, Y. Koshio,A. Takeda, K. Abe, H. Sekiya, H. Ogawa, K. Kobayashi, K. Hiraide,K. Ueshima, A. Shinozaki, H. Nishiie, S. HiranoIPMU, University of Tokyo K. Martens, J.LiuKobe University: Y. Takeuchi, K. Otsuka Saga University: H. OhsumiTokai University: K. Nishijima, D. MotokiGifu University S. TasakaWaseda University S. SuzukiYokohama National University S. Nakamura, I. Murayama, K. FujiiMiyagi University of Education Y. FukudaSTEL, Nagoya University Y. Itow, K. Masuda, H. Uchida, Y. NishitaniSeoul National University S.B. KimSejong University Y.D. KimKRISS: Y.H. Kim, M.K. Lee, K. B. Lee, J.S. LeeKamioka observatry6

DormitoryUnderground LabOffice

Three phases of the XMASS experiment

100kg PrototypeFV:30kg, ~30cm800kg DetectorFV:100kg, 80cm20ton DetectorFV:10ton, ~2.5mDark MatterR&DSolar NeutrinoDark MatterCompleted 2007 : Project was funded. 2010 Sep. : Detector construction was completed 2010 Oct.-: Commissioning777WIMP search in XMASS8

10-310-410-510-6Counts/day/kg/keV 50GeV, scp=3x10-44 cm2Expected recoil energy spectrafor different target nucleiExpected total event ratefor spin independent case

m: reduced massXenon has an advantagedue to its large ADark MatterWIMPDeposit EnergyExpected sensitivity9

XENON10CDMSIIXMASS 1yrSpin Independent Casescp>2x10-45 cm2 for 50-100GeV WIMP, 90%C.L.1yr exposure, 100kg FV,BG: 1x10-4 /keV/d/kgScintillation efficiency: 0.2

Black:signal+BGRed:BGExpected energy spectrum1 year exposurescp=10-44 cm250GeV WIMPMCThe XMASS detector10The XMASS 800kg detector11

Xenon detector Liquid Xenon 857kg 642 PMTs (Hamamatsu R10789) 64.2% photo coverage

Water cherenkov detector shield of gamma, neutrons used for cosmic-ray veto 72 PMTs (20-inch)11m10mWater shield for fast neutrons12

water: 200cm, energy: 10MeVLiq. Xewater< 2 x 10-4 counts/day/kg200cm of water is enoughto reduce the fast neutronX [cm]Z [cm] Fast n flux @Kamioka mine: (1.15+0.12) x10-5 /cm2/sec-MC

Liquid Xenon detector(main detector) 13~ 1.2m642PMTsOFHC coppervessel857kgxenon

Hex : R10789-11Round: R10789-11MOD126.6126.647We developed new ultra low RI PMT with Hamamatsu.(1/100 of ordinary one).

Counts/day/kg/keVkeV Self-shielding for BG from PMTs (MC)

keVCounts/day/kg/keVBG/PMT [mBq]U chain0.70 +/- 0.28Th chain1.51 +/- 0.3140K< 5.1060Co2.92 +/- 0.16< 10-4 /keV/day/kg (100kg F.V.)

PMTPMTn contribution < 2.2x10-5/d/kg g trackingMCMC14Readout electronics15

12bit ADC/TDC (ATM) To cover large energy range8bit Flash ADCFor pulse shape discrimination in low energyPre-amplifier card dynamic range: 0~-1 V sampling rate : 500 MS/s sample number: 8,160 time span : 16.32 usec TKO module ADC dynamic range : 0~400 pC TDC dynamic range : 0~1 usec

PMTCryogenic apparatus16700LLiq. Storageliquid pumpCondenser360Wgas pumpgetterCalibration lineCable linefiltersOuter vacuum857kg10 m3 x 2

gas storageemergency gas pump 100L/minevaporatorWater tankLiquid circulation ~5L/minGas circulation