NEWS: Nuclear Emulsion Wimp Search Natalia Di Marco Laboratori Nazionali del Gran Sasso - INFN

Outline Directional Dark Matter Searches The NEWS idea: a novel approach to directional detection of DM High Resolution Nuclear Emulsions: NIT Detection Principle NEWS R&D actvity Design sensitivity Moriond Cosmology - March 2014 N. Di Marco

Directional Dark Matter Searches WIMP wind Sun 230km/s Earth Earth revolution gives seasonal modulation Due to solar system movement in the galaxy, the WIMP Flux is expected to be not isotropic @earth. A directional measurement would provide a strong signature and an unambiguous proof of the galactic origin of DM Moriond Cosmology - March 2014 Scattered Wimp N. Di Marco Q WIMP cross-section with nuclei  A2 Recoil Nuclei direction

Directional Dark Matter Searches Current approach: low pressure gaseous detector Targets: CF4, CF4+CS2, CF4 + CHF3 Recoil track length O(mm) Small achievable detector mass due to the low gas density ⇒Sensitivity limited to spin-dependent interaction Moriond Cosmology - March 2014 N. Di Marco NEWAGE@ Japan DM-TPC@ USA DRIFT @ UK MIMAC@ France

Directional Dark Matter Searches Use solid target: Large detector mass Smaller recoil track lenght O(100 nm)  very high resolution tracking detector Moriond Cosmology - March 2014 N. Di Marco

Directional Dark Matter Searches Use solid target: Large detector mass Smaller recoil track lenght O(100 nm)  very high resolution tracking detector Nuclear Emulsion based detector acting both as target and tracking device Moriond Cosmology - March 2014 N. Di Marco

Directional Dark Matter Searches Use solid target: Large detector mass Smaller recoil track lenght O(100 nm)  very high resolution tracking detector Nuclear Emulsion based detector acting both as target and tracking device Moriond Cosmology - March 2014 N. Di Marco NEWS: Nuclear Emulsion WIMP search Italy Napoli Univeristy “Federico II” LNGS – INFN Bari University Japan Nagoya University

Nuclear Emulsion AgBr crystal size 0.2-0.3 mm After the passage of charged particles through the emulsion, a latent image is produced. The emulsion chemical development makes Ag grains visible with an optical microscope Moriond Cosmology - March 2014 AgBr crystal size 0.2-0.3 mm A long history, from the discovery of the Pion (1947) to the evidence of nm nt oscillation in appearance mode (OPERA, 2014) N. Di Marco

Sensitivity to low WIMP mass Nuclear Emulsion Ag Br O N C Chemical composition of nuclear emulsions Moriond Cosmology - March 2014 A % Weight I 126.9 0.8 Ag 107.9 28.5 Br 79.9 20.7 S 32.1 1.3 O 16.0 13.7 N 14.0 8.6 C 12.0 23.6 H 1.0 2.9 Lighter nuclei (longer range at same recoil energy) ↓ Sensitivity to low WIMP mass N. Di Marco

WIMP velocity < 800 km/sec Nuclear Emulsion Range [nm] Recoil energy [keV] Ag Br Moriond Cosmology - March 2014 Max recoil energy [keV] WIMP mass [GeV/c2] N. Di Marco WIMP velocity < 800 km/sec Take e.g. MWIMP ~ 150 GeV/c2 Recoil energy < 500 keV Br range < 300 nm OPERA emulsion films: Silver grain size ̴ 200 nm  too large to record nanometric nuclear recoils

NIT emulsion films: Nano Imaging Trackers 35 nm crystal 70 nm crystal 100 nm crystal 200 nm crystal Moriond Cosmology - March 2014 Size R&D Natsume et al, NIM A575 (2007) 439 Recent developments N. Di Marco Range distribution [nm]

Concept of readout: step 0 Film expansion technique (T. Naka et al., NIMA581 (2007) 761) Expansion of emulsion film Chemical treatment Moriond Cosmology - March 2014 N. Di Marco

Concept of readout: step 0 Film expansion technique (T. Naka et al., NIMA581 (2007) 761) Expansion of emulsion film Chemical treatment Moriond Cosmology - March 2014 Signal track Elliptical shape N. Di Marco Random noise Circular shape

Concept of readout: step I Scanning with optical microscope and shape recognition analysis Moriond Cosmology - March 2014 N. Di Marco Automatic selection of candidate signals by optical microscopy. Full area scan. Resolution 200 nm (one order of magnitude better than the OPERA scanning system), scanning speed 20 cm2/h

Concept of readout: step I Scanning with optical microscope and shape recognition analysis Test using 400 keV Kr ions Moriond Cosmology - March 2014 N. Di Marco

Concept of readout: step I Scanning with optical microscope and shape recognition analysis Test using 400 keV Kr ions Moriond Cosmology - March 2014 θ N. Di Marco Direction detected! Nucl.Instrum.Meth. A680 (2012) 12-17 

Concept of readout: step II Scanning with X-ray microscope of preselected zones Moriond Cosmology - March 2014 N. Di Marco Pin-point check at X-ray microscope of candidate signals selected by optical readout. Resolution ̴ 30 nm

Concept of readout: step II Scanning with X-ray microscope of preselected zones 330nm 236nm 486nm 600nm Optical microscope X-ray microscope Moriond Cosmology - March 2014 N. Di Marco

Concept of readout: step II Scanning with X-ray microscope of preselected zones 330nm 236nm 486nm 600nm Optical microscope X-ray microscope Matching of recoiled tracks between Optical and X-ray microscope Moriond Cosmology - March 2014 Success rate of matching 572/579=99% N. Di Marco

Concept of readout: step II Scanning with X-ray microscope of preselected zones 330nm 236nm 486nm 600nm Optical microscope X-ray microscope Matching of recoiled tracks between Optical and X-ray microscope Moriond Cosmology - March 2014 Success rate of matching 572/579=99% N. Di Marco angular resolution [degrees] optical microscope 31.4 +- 4.7 degree @original range: 150-250nm X-ray microscope 16.8+-2.9 degree @original range: 150-250nm

R&D activity NIT technology Optical and X-ray read-out system Intrinsic background measurement Angular resolution measurement, neutron test beam Full MC simulation Moriond Cosmology - March 2014 N. Di Marco

R&D activity NIT technology Optical and X-ray read-out system Intrinsic background measurement Angular resolution measurement, neutron test beam Full MC simulation Moriond Cosmology - March 2014 N. Di Marco

Sensitivity Zero-background hypothesis 90% C.L. 100 nm tracking threshold directionality information not included Moriond Cosmology - March 2014 N. Di Marco

Conclusions A novel approach for directional Dark Matter searches is proposed in NEWS Novel nuclear emulsion technique with nanometric spatial resolution The use of a solid target would allow to explore the low cross section sector in the phase space indicated by recent direct search experiments but using a complementary an powerful approach NIT (Nano Imaging Tracker) Read-out system based both on optical (200 nm resolution) and X-ray microscopy (30 nm resolution) … from the R&D to the experiment in few years Moriond Cosmology - March 2014 N. Di Marco