1. Detecting WIMPs using Au-DNA Microarrays
Martha Cassetti April 24, 2013
Detecting WIMPs using Au-DNA Microarrays

2. Weak Interacting Massive Particles (WiMP)
Dark Matter Candidate
23% of all matter, Galactic halo
Transparent to strong and EM force
Lightest Super-symmetric particle
1GeV-10TeV range
Recent Experimental Evidence (CDMS, CoGent, DAMA, CRESST-II, AMS)
Inconclusive
Fast Neutrons, radioactive showers, faulty detectors??

3. Detection Methods Non-zero Wimp-Nucleon interaction cross section
Deposits 1-10KeV to nucleus
Indirect measurements
High energy neutrino production from WIMP/solar nuclei interactions
Direct measurements
Sensitive detectors, scaled to large volumes

4. Ex:CDMS(Cryogenic Dark Matter Search)
Cryogenically cooled Ge- Crystals
Superconducting phase
Recoil nuclei, lattice vibrations
Measurable change in resistance
Germanium and silicon “Hockey Puck” Detectors at CDMS at Soudan Mine in MN

5. Annual and Diurnal Modulation

6. Alleged wimp Events: TWO this month!!
SuperCDMS: 3 events at ~3σ (Submitted:15 April 2013)
Alpha Magnetic Spectrometer: (Published:3 April 2013)

7. Alleged WIMP EVENTS DAMA: Annual Modulation over 13 cycles ~9σ
Incompatible with similar experiments
CoGeNT: (16 Mar 2010)
Annual modulation ~2.8σ (promising)
CRESST-II: 67 events in acceptance region (4 Sep 2011)
??? Weird
CDMS-II: 2 events in 2010,
No annual modulation (6 March 2012)
Null Results: XENON10, XENON100, CDMS, EDELWEISS
All events ~10 GeV and cross section ~1040 cm2* *

8. Problems Threshold energy at detection limit! 10KeV Ge/Si, 16KeV Xe
Similar signals: Fast Neutrons from cosmic ray events
Range of recoiling nuclei is super short !
𝐸∝ 𝑍 2
Low density detectors to increase recoil range scaled to large volumes (ex: DRIFT, XENON)

9. Why DNA detector Nanometer resolution (one base unit ~0.7nm stretched)
Energy scales: Threshold ~0.5KeV
Directional sensitivity ~100 events
Room Temperature operation
Ability to amplify signal ~106 fold using PCR
Clever background elimination (dE/dx)

10. DNA detector: Au-Microarrays
Basic Design: Au foil with DNA current, “book stacked”
Au Nuclei striking DNA “Forest” ~1000bb ( μm), 10KeV Au recoil
~1 kg Au, 0.1kg DNA packed into (1m)3 ,10 nm spacing

11. “Artist’s” Rendition of DNA Microarray

12. Recoil Path
Recreate recoil path: Polymerase Chain Reaction + ssDNA sequencing!!
Cut ends are labeled with a primer.
DNA Polymerase attaches to primer,
Takes nucleotides from environment, rebuilds specific sequence.
The process is exponential, 106 fold amplification!
ssDNA sequencing gives order of base pairs!

13. Background Elimination
Tail-Head Asymmetry
Striking order
Can estimate distance WIMP event travelled by looking at stopping power!!
One layer of AU-ssDNA to stop WIMPs
CR,γ,α,β penetrate 100+ stacks
DNA contains radioactive C14 and K41
Old Carbon/Replace Potassium

14. Conclusions Nanometer resolution Energy Thresholds
Directionality and Path Reconstruction
Still Problematic:
Fast neutrons, low recoil energy
Synthesizing DNA with >1000bp (ideally 10,000bp)
Reconcile current WIMP evidence!??

15. To Be Continued…..Questions???
New search for dark matter detectors using DNA for nanometer tracking:
Dark Matter Search Results Using the Silicon Detectors of CDMS II:
Search for annual modulation in low-energy CDMS-II data:

16. Back up slides