1. Directional Dark Matter Search with Nuclear Emulsion Tatsuhiro Naka Nagoya University Cosmic Frontier Workshop at SLAC, USA, 6-8 March, 2013

2. Nuclear Emulsion Detector -3D tracking detector - solid state detector (3-4 g/cm 3 ) - high spatial resolution - very stable to increasing in size 50 µm Charged ParticleSilver halide crystal (AgBr) Development treatment Silver grains Polymer (C, (N,O)) Epi-illuminated dark field optics image

3. 10 GeV/c 2 DM Track length [nm] ― : C (N,O) ― : Br ― : Ag Direction sensitive Detector Detection of recoiled nuclei as tracks Target nuclei DM Direction of solar system (230km/sec) earth@summer earth@winter Dark matter wind Directional Dark Matter Search with Nuclear Emulsion -Another methods with different systematic from annual modulation are required. -Statistics of 1/10 – 1/100 to annual modulation measurement ⇒ high reliability - Study of velocity distribution for DM Mount on the equatorial telescope and play a detector on CYGNUS direction. sun

4. Detector Production Self production and R&D in Nagoya University, Japan from Apr., 2010 Production ability : ～ 2 kg emulsion detector / week Pouring on base We just started to design for a lager scale machine. ⇒ We will produce the detector of 10 kg within 2-3 years Ratio of fiducial volume is more than 80 %.

5. Detectable length 500nm 35 nm crystal 70 nm crystal 100 nm crystal 200 nm crystal 500nm Kr 400keV Scanning Electron Microscope 200nm Kr 200keV Range distribution [nm] 100 nm detectable Corresponds to about 40 keV C (N,O) recoil tracks.

6. Minimum crystal size Mean : 18.0 +- 0.2 [nm] sigma: 4.9 +- 0.2 [nm] Crystal size [nm] - reduce the tracking energy threshold - background rejection ⇒ lower sensitivity for electrons ⇒ noise discrimination by increase of number of silver grains forming the tracks We sill study about sensitivity control for practical application.

7. Prototype of readout system Japan System for R&DEuropean System for R&D Nagoya University (Japan) University of Napoli (Italy) LNGS (Italy) - We started to construct the R&D readout system with optical microscope. - Now, it became possible to readout the signals all automatically.

8. Automatic selection of candidate signals by optical microscopy. Optical microscope Readout X-ray microscope Readout @ SPring-8 Pin-point check of candidate signals selected by optical readout. Record of Position information for the events passed the signal selection filter. Confirmation of signal! 70 nm line/70 nm space Δx is better than 70 nm. Concept of readout tracks

9. Demonstration using heavy recoil nuclei tracks induced by 14 MeV neutron (D-T nuclear fission reaction) 632 nm337 nm308 nm 217 nm 592 nm392 nm Mostly Br recoil (170 - 600keV) because of low sensitivity tuning.

10. 330nm 236nm 486nm 600nm Optical microscope X-ray microscope Demonstration of Matching of recoiled tracks between Optical and X-ray microscope Success rate of matching 572/579=99%

11. Signal Selection by Optical microscope system signal region Red: tracks Blue: Noise Major length[pix] minor length[pix] Major Minor Readout efficiency θ Optical readout results of events confirmed as tracks and noise by X-ray microscopy analysis. Cos (2D angle) Visible Track length [nm]

12. Ideal sensitivity of emulsion detector SI limit [25 kg ・ year R>125 nm] SI cross section [log 10 σ] We already have experience of 100-1000 kg emulsion detector. (e.g. DONUT, CHORUS experiment)

13. Low velocity ion created by an ion-implantation system Angular resolution of optical MS readout 2D angle [rad.] ― : data ― : MC simulation Angular distribution of 100 keV C ion Angular resolution is better than about 25 deg. for 80 keV C recoil tracks. Ang. Resolution will be better with confirmation of X-rays microscope.

14. Gran Sasso (LNGS), Italy R&D underground facility in Gran Sasso 2 nd Floor: Detector Production 1 st Floor : Development Facility

15. Study of self-production method for fine grained nuclear emulsion Construction of readout system based on the optical microscope R&D of X-ray microscope and pin-point checking system at BL47, 37XU of SPring8 2011 2013 2012201420152016 Construction of R&D facility at Gran Sasso Sensitivity tuning for phase.1 type and stability check Start of BG study and R&D for BG discrimination (neutron, electrons) Standard run + R&D of large emulsion setting and high contrast 1 – 10 g scale BG study Sensitivity tuning for fine grained emulsion Scale-up BG study and upgrade for high-speed and high-resolution Facility and Run X-ray microscope system Optical readout system Detector study Status and Near future R&D Plan

16. Summary and Challenging We developed the high resolution nuclear emulsion detector for directional dark matter search and self-production of it is possible. Detection of submicron tracks (> 100nm length) is possible. Readout system with optical microscope and X-ray microscope is ready. These have been demonstrated by mono. neutron. ⇒ readout efficiency > 80 % @ 200 nm visible length (60 keV C range) We will start the background study and small scale BG run from this year. Background rejection ( especially, C-14 will be serious backgrounds ⇒ ~ 10^6 /kg/days ) ⇒ we study about rejection method (e.g., small crystal, sensitivity control, new develop treatment and new optical readout algorithm) Higher spatial resolution of optical microscope ⇒ new design of objective lens and short wavelength scanning. noise reduction ⇒ more than 3 grains tracking and making difference for the size between noise and signals (Plasmon Analysis). Challenging

17. Nagoya University T. Naka (Organizer of Japan and all) T. Asada ( R&D of fine-grained emulsion ) T. Katsuragawa ( Readout system) M. Yoshimoto (Optical Readout Stage) K. Hakamata (Development treatment) M. Ishikawa (Plasmon analysis study) K. Kuwabara (R&D of emulsion) M. Nakamura (PI) T. Nakano (Scanning system) O. Sato (analysis) Nagoya University [ X-ray Astronomy] Y. Tawara (X-ray microscope) University of Napoli G. de Lellis (Organizer of Europe) A. Di Crescenzo (DM simulation) A. Sheshukov (Emulsion simulation) A. Aleksandrov (Optical stage study) V. Tioukov (tracking algorithm) University of Padova C. Sirignano (Development and emulsion study in Gran Sasso) LNGS N. D’Ambrossio (Optical microscope study in LNGS) N. Di Marco F. Pupilli SPring.8 Y. Suzuki (X-ray MS @ BL47, 37XU) A. Takeuchi (X-ray MS @ BL47XU) K. Uesugi (X-ray MS @ BL47XU) Y. Terada (X-ray MS @ BL37XU) Chiba University K. Kuge (emulsion and development study) Fuji Film researcher T. Tani (Emulsion and phenomenology) K. Ozeki (Emulsion and phenomenology) Saito (the machine technology) Collaborator and Technical Supporter

18. Back up

19. Red : best focus layer Blue : de-focus layer Z[micron] Mean value of brightness Definition of best focus Best focus automatic selection

20. Event images of each focus Mean brightness 58.6 68.5 87.0 116.3101.9109.3 64.777.757.0 Best Focus Step of layer taking 0.2μm 30pix 1pix=57nm 1pix=57nm

21. Neutron Source [Advanced Industrial Science And Technology, Tsukuba, Japan] 14.8MeV neutron source by nuclear fission 2 D + 3 T → 4 He + n 14.8MeV neutron

22. Confirmation by X-ray microscope SPring-8 @ Japan 8keV X-ray Zone plate Zernike phase plate -Thickness of film : 100µm -Focal depth : 70µm -Type of optics: phase contrast -X-ray Energy : 8keV It is possible to analysis of 1000 events /day. System is almost ready for realistic dark matter search.

23. SPring-8 BL47XU BL47XU Ta 100 nm thickness pertarn on SiN membrane (2µm) Ta 8 keV, δ = 4.0E-5, β = 3.7E-6 [c.f. Ag 8 keV, δ = 3.0E-5, β = 2.7E-6] Camera : CMOS (HAMAMATSU) 2048(H) x 2048(V) 6.5 µm(H) x 6.5 µm(V) cell size Phase Plate : Zernike phase plate ( π/4λ shift)

24. Mounting test

25. How to coverage FOV with Imager  5mm Effective FOV5.1×4.9 mm 2 Effective pixel size0.45  m (120Mpixel/FOV) Repetition time0.10 sec /16depth/FOV -> >300fps Max. scan speed9000cm 2 /h FOV of SUTS FOV of New Scanning System 1 2 3 4 5 6

26. Pixel pitch : 5.5  m (2048×1088) Effective area : 11.264mm × 5.984mm Package dimension : 18.65mm × 13.50mm Sensor pitch : 20.55mm × 15.98mm 1868×2 × 909×3 Frame rate : up to 340fps FOV: 25mm 2 ×16.6%×6 Mosaic Camera for Hyper-TS