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Proposed dark matter detector - how does it work?

  1. Jul 19, 2012 #1
    A few weeks ago I stumbled upon an MIT Technology Review article about a DNA-based dark matter detector. As a biologist I thought the idea was strange, since I didn't see how DNA would interact with dark matter in a way that a more easily manufacturable material such as silicon wouldn't. I put off reading the article until today and now that I have, I still don't get the fundamental premise.

    First, a link to the article: http://www.technologyreview.com/view/428391/revolutionary-dna-tracking-chamber-could-detect/

    The idea seems to be that you have an array of single stranded DNA attached to a gold chip. A "dark matter particle" transfers kinetic energy into a gold nucleus, sending it flying through the DNA array and severing the chemical bonds along its trajectory. The severed DNA is collected, amplified via PCR (a molecular biology technique for rapid DNA replication, for those who haven't heard of it), and sequenced. Since each DNA strand in the array has a different sequence, the identity of the severed DNA strands provides a record of the 3-dimensional direction in which the gold nucleus traveled. This is then compared to the time of day to test the hypothesis that the earth travels into the dark matter field while rotating towards Cygnus, and away from it while rotating away from Cygnus.

    Since I have no knowledge at all about dark matter, I have a couple questions about the proposed detector.

    1: Is there any evidence that dark matter interacts with gold? Why particularly gold instead of another element?
    2: If there is such evidence, why rely on a prototype, expensive, never-before-tested DNA-based detector rather than a detector film such as that used for Rutherford backscattering analysis or other surface science techniques?
    3: If the detector is built and produces a signal, would it be reasonable to assume that the signal comes from dark matter rather than any other process such as residual radioactivity that could knock out a nucleus?

    Thanks!
     
  2. jcsd
  3. Jul 19, 2012 #2

    jedishrfu

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  4. Jul 19, 2012 #3

    mfb

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    I agree that gold is probably chosen for its chemical properties - no corrosion, easy to handle, maybe it is easy to attach DNA?

    Weakly interacting particles could interact with all matter in some way, heavy nuclei might have a bigger cross-section (as they just have more matter inside).

    There are conventional detectors searching for dark matter, but if the energy of the moving atom is very low, it is hard to detect it with them. As far as I understand the article, the DNA detector gives a short 3-dimensional track of high precision for signal events, and long tracks (in multiple layers) for background radiation. Conventional detectors have a resolution of ~50µm, a nanometer-precision would be a big step.
     
  5. Jul 20, 2012 #4
    Interesting , clever idea at that.
     
  6. Jul 20, 2012 #5

    Chronos

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    Gold has a heavy nucleus giving it a high cross section, which means it presents a bigger target for a collision with a DM particle.
     
  7. Jul 20, 2012 #6

    Ryan_m_b

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    Fascinating. I wonder why PCR though, I would have thought a DNA cantilever/optical tweezers would have worked far better and been less fiddly. Perhaps the energy is too high?
     
  8. Jul 20, 2012 #7

    mfb

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    PCR is just a method to amplify the signal (the splitted segments of DNA) - instead of a single DNA pattern, you get 10^x which can be identified with chemical methods.
     
  9. Jul 20, 2012 #8

    Ryan_m_b

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    I'm not sure if you were replying to me but if you were I fully understand what PCR is (cue flashback to hours and hours of undergrad research). My point though was that with an optical tweezer you could detect the impact in real time, get more information about it such as the energy involved and it would be non destructive.
     
  10. Jul 20, 2012 #9

    mfb

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    How do you get a 3-dimensional track plus a momentum measurement of a slow, free atom with optical tweezers?
    If the background level is low enough, real-time measurements are not required.
     
  11. Jul 20, 2012 #10
  12. Jul 20, 2012 #11
    I'm wondering if you could use this for a general neutrino telescope. You make up for the low detection rates by integrating the detector over time.
     
  13. Jul 20, 2012 #12
    I'm wondering how long you could use such a chip for. Once the DNA strand is cleaved, it's gone. I have no idea what the interacting particle density would be; if you have a lot of gold nuclei flying around you could quickly destroy the detector. How is it going to be isolated so that background radiation doesn't kill the detector before a signal is found?
     
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