NEWS: Nuclear Emulsion Wimp Search

1. NEWS: NuclearEmulsionWimpSearch Natalia Di Marco Laboratori Nazionali del Gran Sasso - INFN

2. 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 N. Di Marco

3. Earth WIMP wind Sun 230km/s Q Directional Dark MatterSearches 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 Scattered Wimp N. Di Marco WIMP cross-section with nuclei  A2 Recoil Nuclei direction

4. Directional Dark MatterSearches 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 N. Di Marco DRIFT @ UK DM-TPC@ USA NEWAGE@ Japan MIMAC@ France

5. Directional Dark MatterSearches Use solid target: • Large detector mass • Smaller recoil track lenght O(100 nm)  very high resolution tracking detector N. Di Marco

6. Directional Dark MatterSearches 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 N. Di Marco

7. Directional Dark MatterSearches 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 N. Di Marco NEWS: Nuclear Emulsion WIMP search • Italy • Napoli Univeristy “Federico II” • LNGS – INFN • Bari University • Japan • Nagoya University

8. NuclearEmulsion After the passage of charged particles through the emulsion, a latent image is produced. The emulsion chemical development makes Ag grains visible with an opticalmicroscope AgBrcrystalsize 0.2-0.3 mm A long history, from the discovery of the Pion (1947) to the evidence of nm ntoscillation in appearance mode (OPERA, 2014) N. Di Marco

9. NuclearEmulsion Chemical composition of nuclear emulsions O N C Lighter nuclei (longer range at same recoil energy) ↓ Sensitivity to low WIMP mass Br N. Di Marco Ag

10. NuclearEmulsion Ag Br 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 Range [nm] OPERA emulsionfilms: Silver grainsize ̴ 200 nm  too large to record nanometricnuclearrecoils Recoil energy [keV]

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

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

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

14. Concept of readout: step I Scanning with opticalmicroscope and shaperecognitionanalysis 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

15. Concept of readout: step I Scanning with opticalmicroscope and shaperecognitionanalysis Test using 400 keV Kr ions N. Di Marco

16. Concept of readout: step I Scanning with opticalmicroscope and shaperecognitionanalysis Test using 400 keV Kr ions N. Di Marco θ Direction detected! Nucl.Instrum.Meth. A680 (2012) 12-17 

17. Concept of readout: step II Scanning with X-raymicroscope of preselectedzones N. Di Marco Pin-point check at X-ray microscope of candidate signals selected by optical readout. Resolution ̴ 30 nm

18. Concept of readout: step II Scanning with X-raymicroscope of preselectedzones Optical microscope 486nm X-ray microscope 236nm N. Di Marco 330nm 600nm

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

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

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

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

23. Sensitivity • Zero-background hypothesis • 90% C.L. • 100 nm trackingthreshold • directionality information notincluded N. Di Marco

24. Conclusions • A novelapproach for directional Dark Mattersearchesisproposed in NEWS • Novelnuclearemulsiontechnique with nanometricspatialresolution • 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 systembasedboth on optical (200 nm resolution) and X-raymicroscopy (30 nm resolution) … from the R&D to the experiment in fewyears N. Di Marco