Detecting WIMPs using Au-DNA Microarrays Martha Cassetti April 24, 2013 Detecting WIMPs using Au-DNA Microarrays
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?? http://zebu.uoregon.edu/~soper/Mass/WIMPS.html
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
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 http://www6.slac.stanford.edu/news/2013-04-15-cdms-results.aspx
Annual and Diurnal Modulation http://www.quantumdiaries.org/wp-content/uploads/2012/03/Wimp-wind.jpg
Alleged wimp Events: TWO this month!! SuperCDMS: 3 events at ~3σ (Submitted:15 April 2013) Alpha Magnetic Spectrometer: (Published:3 April 2013)
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* *http://arxiv.org/pdf/1207.3039.pdf
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)
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)
DNA detector: Au-Microarrays Basic Design: Au foil with DNA current, “book stacked” Au Nuclei striking DNA “Forest” ~1000bb (0.3-0.7μm), 10KeV Au recoil ~1 kg Au, 0.1kg DNA packed into (1m)3 ,10 nm spacing
“Artist’s” Rendition of DNA Microarray
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!
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
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!??
To Be Continued…..Questions??? New search for dark matter detectors using DNA for nanometer tracking: http://arxiv.org/abs/1206.6809 Dark Matter Search Results Using the Silicon Detectors of CDMS II: http://arxiv.org/abs/1304.4279 Search for annual modulation in low-energy CDMS-II data: http://arxiv.org/abs/1203.1309
Back up slides http://profmattstrassler.com/2013/04/03/ams-presents-some-first-results/