Dark but not Too Dark? Experimental Efforts to Detect Dark Matter
Brian Odom, Northwestern University
A broad range of astrophysical observations strongly suggest that most matter in the universe, so-called dark matter, is made of particles not yet discovered on earth and not accounted for within the current framework of physics. These dark matter particles evidently do interact with normal matter through gravity, but not via the much stronger electromagnetic or strong nuclear forces. While observations of far-away gravitational interactions give convincing evidence for the existence of dark matter, they can do very little to elucidate its properties.
In order to determine the precise nature of dark matter, either “direct detection” or “indirect detection” would be required. Attempts at direct detection depend on the constant flow of dark matter through the earth. Direct detection experiments attempt to observe energy deposited in a detector as a result of collisions between dark matter particles and the detector material. Since it would be the well-named weak nuclear force giving rise to these collisions, events are expected to be quite rare, and much ingenuity is required to reduce false signals from natural radioactivity. Indirect detection experiments attempt to observe various types of secondary particles which might be created in dark matter on dark matter collisions. Astrophysical regions where such collision occur include the sun, the center of the Milky Way, and the early universe. Presently, a few interesting claims of direct and indirect detection remain unconfirmed, and many active research programs around the world are racing to achieve the first definitive detection of dark matter.
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