方向に感度を持つ検出器での 暗黒物質探索 ～ NEWAGE project ～ 京都大学 理学研究科 助 手 身内賢太朗 With μ-PIC 開発グループ 谷森達、窪 秀利 竹田敦、永吉勉、 折戸玲子、植野優、 高田淳史、岡田葉子 Direction Sensitive WIMP-search with an Advanced Gaseous tracking Device TALK PLAN 1. NEW ： WIMP-wind 2. AGE ： -TPC 3. NEWAGE : DM search with -TPC 4. Road to the NEWAGE 2003 Oct. 16, TEA03 “New direction of particle physics” First paper will appear in PLB.
Dark Matter : two results reported in 2003 WMAP : m h 2 = DAMA (100kg NaI) : seven years’ observation NASA/WMAP Science Team 1. Direction-sensitive WIMP-search : WIMP-WIND Other exps. say “NO” to DAMA PLB545(2002)43 astro-ph/ : DAMA’s “signal”
Investigate DAMA’s region (and deeper) with a more reliable method DAMA and other exps. : Annual modulaiton Alternative method : Direction Sensitive WIMP-search Direction Sensitive WIMP-search
WIMP-wind Annual modulation - rate difference : a few% “WIMP-wind” Scintillators - Tokyo Gas detectors - DRIFT （ UK ） - NEWAGE （ Kyoto ）
2. Advanced Gaseous tracking Device : -TPC Preceding project : DRIFT(UK) MWPC with 2mm pitch 2-D tracks only Our “AGE”: -TPC 400 m pitch 3-D tracks research/pa/DRIFT.html 1m electron (~100 keV) and proton (0.8GeV) tracks detected by our -TPC 10cm ~×10 sensitivities
Properties of -TPC KEY device: -PIC - 2D gaseous imaging detector - Printed Circuit Board technology large area, cheap - No 3D geometry mechanically-stable 400 μ m We are developing 30×30cm 2 –PIC now. 10×10cm 2 10×10cm 2 –PIC works very well.
Gain mapCathode Anode V A = 560V Performance of -PIC Gas gain ~ gain uniformity~ 7 No ion feedback Test chart X-ray image (Xe:C 2 H 6 7:3)
30cm 40cm μ-PIC encoder 5 FPGAs anode–cathode 20MHz pre-amplifier ATLAS ASD Readout electronics READY FOR SCALING UP
“Bragg curve” Performance of -TPC 10×10×8cm 3 μ-TPC : developed Tracking including the direction （ >3mm ） Fine spatial resolution (2D ： 120μm, 3D ： 320μm)
dE/dX [keV/cm] χ 2 /d.o.f dE/dX [keV/cm] 252 Cf (n+γ) 22 Na (γ) nucleus event Background rejection Particle I.D. (DM: nucleus BG-gamma: electron) >95 ％ gamma-ray rejection (very preliminary study) Experimental results Simulations （ 25keV F ion in 20 Torr CF 4 ） 2mm c.f. 25keV electron ： >10cm
3. NEWAGE : DM search with -TPC Expected WIMP-signals Recoil angle distribution Forward-backward asymmetry WIMP WIND γ F F hatched ： WIMP painted ： neutron BG Simulation conditions: Kamioka 50 water shield -ray BG 100% rejected CF 4 20Torr track>3mm Eth=25keV
Sensitivities “Detection” by Forward/Backward 3σasymmetry Simple and reliable Xe for Spin-Dependent CF 4 for Spin-Independent Xe for Spin-Dependent CF 4 for Spin-Independent New Journal of Phys.2(2000)14 SD SI
4. Road to the NEWAGE -ray BG rejection Electron diffusion Long term operation Low pressure operation NEWAGE eve (R&D with 30cm cube) BRAND-NEWAGE (1m 3 ×30) ? NEWAGE (1m 3 ) 1m 3 micro-TPC NEO μ-PIC Drift plane micro-TPC 27m 3 WATER 50cm Smith
SUMMARY Detecting the WIMP-wind by direction- sensitive method Much more reliable method ｔｈａ n annual modulation Now μ-TPC is at hand, so why don’t we open up the NEWAGE? ご支援よろしくお願いいたし ます。
SUSY neutralino gaugino + higgsino Spin-independent (SI): H, h, squark exchange Spin-dependent (SD): Z, squark exchange
Cross section Enhancement factor C SI interaction A: atomic number A: atomic number SD interaction (contribution of either proton or neutron is considered) λ: Lande factor J : total spin of the nuclei Isotopeunpaired abundanc e λ 2 J(J+1) 7 Li p92.5% F p100% Na p100% Ge n7.8% I p100%0.023
μ-PIC の改良 アノード収集効率 30 ->97% アノード付近 65-> 2% カソード間 4 -> 1% Drift end points -20um +10um 3 次元電場計算 New μ-PIC
Pressure / Threshold / Track-length length>3mm
Recoil angle distribution simulation WIMP WIND γ F F hatched ： WIMP painted ： neutron (fast neutron 1.9e-6 n/s/cm2) with 50cm water shield -ray BG 100% rejection CF 4 20Torr (90g/m3) track>3mm, Eth=25keV exposure : 3m 3 year
Full-tracking and semi-tracking
Electron diffusion < 1mm for 50cm drift length (astropatr. phys. 8 (1997) 43) to be studied
Angular resolution of the trackings Multiple scatterings of ions Better than 30 degree