Slide 1

Recent progress of direct dark matter detection S. Moriyama Institute for Cosmic Ray Research, University of Tokyo Oct. 8 th, 2011 @ FPUA2011, Okayama, Japan Slide 2 Principle of direct detection in Lab. Dark matter hit detectors in Lab. Why interaction expected? Assume DM particles were thermally generated. They annihilated into ordinary matter. This implies an interaction between dark matter and ordinary matter (atoms). Weakly Interacting Massive Particles (WIMPs) Dark matter Ordinary matter Annihilation Scattering 1/temperature ~ time Comoving number density Slide 3 How much dark matter around us? It can be estimated by measuring rotational curve of the galaxy. Local density ~ 0.3GeV/cc ~average x 10 5 Isothermal, Maxwell distribution ( ~230km/s, ~10 -3 ). R.P.Olling and M.R.Merrifield MNRAS 311, 369- (2000) Buldge Steller disk Dark Halo These dark matter particles are expected to cause nuclear recoils even in underground lab. Slide 4 Signals after nuclear recoils Small energy depositions (m p 2 /2 < 1keV), rare. Scintillation light (photons), ionizations, phonons, etc are expected to be observed. By combining multi. info., BG reduction is possible. Scintillation lights + + + + + + - - - - - - Ionization signals Phonon signals...... Bubble generation Slide 5 Expected energy spectrum of nuclear recoil, ~O(10keV) Coherent interaction with each nucleon in nuclei causes enhancement. Target nuclei with similar mass to DM is the best choice. Si Ge Xe Si Xe Ge Red: differential, Blue: integrated R.J.Gaitskell, Ann. Rev. Part. Sci., 54 (2004) 315. Slide 6 Another aspect: annual modulation Due to a peculiar motion of the solar system inside the galaxy, relative velocity to the rest frame of dark matter varies over a sidereal year. This causes the modulation of event rates and energy spectrum. Slide 7 Unknown: mass and cross section! Small mass: low energy threshold detector with light nucleus ~O(GeV/c 2 ) Small cross section: massive and low BG detector ~O(1/day/ton) 3 orders/15years! Mass of dark matter particle UNKNOWN cross section to nucleon UNKNOWN True parameter Detector with larger mass, longer exposure and lower background Detector with smaller atomic number and low energy threshold Slide 8 Experiments all over the world >30! XMASS NEWAGE PICO-LON NIT KIMS PICASSO CDMS CoGeNT COUPP DEAP/CLEAN SIMPLE DMTPC LUX DAMA/LIBRA XENON CRESSTII EDELWEISS ZEPLIN DRIFT WARP ArDM ANAIS MIMAC ROSEBUD PANDAX CDEX DM-Ice Not complete TEXONO Strong tension exists among experiments. DAMA, CoGeNT, CRESSTII XENON, CDMS Slide 9 1. DAMA/NaI (7yr), DAMA/LIBRA (6yr), 430td Antonella, TAUP2011 Slide 10 Positive signal of annual modulation Radioactive pure NaI(Tl): scintillation only, no PID. Strong signature of the annual modulation, ~9 A lot of criticisms at the beginning, but later serious study/consideration started (light DM, IDM, etc.). Influences of seasonal modulating cosmic muons? An unnatural background shape is in doubt. by Sep. 2009 Modulation of +/-2% Slide 11 2. CoGeNT (Ge) 140kgd P-type point contact detector has very low noise thus low energy threshold due to small cap. smaller-mass DM w/ ionization only Science 332 (2011) 1144 PRL 101, 251301 (2008) arXiV1106.0650 0 Slide 12 Assume all the unknown events from DM Mod. ( 2 /dof=7.8/12) 80%C.L. accept. Flat ( 2 /dof=20.3/15) 84% C.L. reject. modulation is favored with 99.4% C.L. Is the contamination of surface background well controlled?? Slide 13 3. XENON100, 4.8td Particle ID possible BG red. Rafael, TAUP2011 Slide 14 Observed data and calibration 3 events remained 1.8+/-0.6BG expected (28%) Observed data Neutron source (causes nuclear recoil) calibration data 99.75% rejection line and 3 sigma contour of NR 99.75% rejection line and 3 sigma contour of NR DM search window (8.4-44.6keVnr) Nuclear recoil e/gamma Slide 15 Status of dark matter search DAMA, Na, 3 DAMA, I, 3 CoGeNT (Ge)90% 5-7GeV O. Buchmueller et al. CMSSM (68%, 95%) arXiv:1106.2529 Including 2010 LHC XENON100 (Xe) CRESST 2 3 orders of sensitivity improved over last 15 years! CDMS (Ge) +CDMS(LE), XENON10(LE) Slide 16 Recent signals of DM, axion, and 2000: DAMA experiment (Gran Sasso) started to claim the observation of dark matter. 2005: PVLAS collaboration (INFN) axions? 2010/2011: CoGeNT (Soudan, US) 2011: CRESST II (Gran Sasso) 2011: OPERA (Gran Sasso, CERN) observation of super-luminal neutrinos Slide 17 Recent signals of DM, axion, and 2000: DAMA experiment (Gran Sasso) started to claim the observation of dark matter. >8 now 2005: PVLAS collaboration (INFN) axions? withdrawn 2010/2011: CoGeNT (Soudan, US) 2011: CRESST II (Gran Sasso) 2011: OPERA (Gran Sasso, CERN) observation of super-luminal neutrinos Italian signals Further experimental check necessary Slide 18 XMASS experiment Slide 19 The XMASS collaborations Kamioka Observatory, ICRR, Univ. of Tokyo Y. Suzuki, M. Nakahata, S. Moriyama, M. Yamashita, Y. Kishimoto, Y. Koshio, A. Takeda, K. Abe, H. Sekiya, H. Ogawa, K. Kobayashi, K. Hiraide, A. Shinozaki, S. Hirano, D. Umemoto, O. Takachio, K. Hieda IPMU, University of Tokyo K. Martens, J.Liu Kobe University: Y. Takeuchi, K. Otsuka, K. Hosokawa, A. Murata Tokai University: K. Nishijima, D. Motoki, F. Kusaba Gifu University S. Tasaka 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, H. Takiya Sejong University Y.D. Kim KRISS: Y.H. Kim, M.K. Lee, K. B. Lee, J.S. Lee 41 collaborators, 10 institutes Slide 20 Kamioka Observatory 1000m under a mountain = 2700m water equiv. 360m above the sea Low cosmic ray flux (10 -5 ) Horizontal access Super-K for physics and other experiments in deep underground KamLAND (Tohoku U.) By courtesy of Dr. Miyoki Slide 21 XMASS experiment 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 was a good candidate to satisfy scalability and low background. As the first phase, an 800kg detector for a dark matter search was constructed. Y. Suzuki, hep-ph/0008296 10ton FV (24ton) 2.5m Solar, 0 , DM in future 100kg FV (800kg) 0.8m, DM First phase Slide 22 Structure of the 800kg detector Single phase liquid Xenon (-100 o C, ~0.065MPa) scintillator 835kg of liquid xenon, 100kg in the fiducial volume 642 PMTs 5keV electron equiv. (~25keV nuclear recoil ) thre. Slide 23 BG reduction by self shielding effect Photo electric effect starts to dominate @500keV: strong self shielding effect is expected for low energy radiations. E (keV) Attenuation length (cm) water ~O(500keV) Photo Electric Effect Compton effect 10cm 1cm LXe Slide 24 Event reconstruction Slide 25 Demonstration of the detector performance Calibration system Introduction of radioactive sources into the detector.