Dark matter is one of the great mysteries of modern science. Astronomers are aware about the existence of this elusive substance, since they can observe its effects on other objects in the universe. However, no one has been able to directly see it. Dark matter is of particular interest to scientists because they make up about 85% of all the mass in the cosmos.
(Photo : Wikimedia Commons/ NASA/ESA/Richard Massey (California Institute of Technology))
Search for Axions
Looking around the universe, some kind of substance can be seen exerting enough gravity to pull on stars, galaxies, and passing light. This substance is called dark matter because no telescope or device has ever directly picked up the source of this force. What the experts know is that something is there and it could take many, many forms.
Experts have mapped out several of the most likely options for places and forms to look. Usually, the approach has been to make detectors that will thoroughly search one specific area in order to rule it out.
Scientists from University of Chicago and Fermi National Accelerator Laboratory explored a different approach. Their technique includes a "broadband" to allow them to search a larger set of possibilities, although it would be slightly less precise.
Dubbed as the Broadband Reflector Experiment for Axion Detection (BREAD), this technique will look for one possible form of dark matter called "axions" or "dark photons". These are particles with extremely small masses which can be converted into a visible photon under the right circumstances.
The BREAD detector consists of a metal tube that contains a curved surface for catching and funneling potential photons to a sensor at one end. In its full-scale version, it will be settled inside a magnet to generate a strong magnetic field, increasing the chances of converting dark matter particles into photons.
The researchers ran the experiment sans magnets. For almost one month, the collaboration ran the prototype device at University of Chicago where data analysis was also carried out.
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Small Step Forward
On March 28, the team published their findings entitled "First Results from a Broadband Search for Dark Photon Dark Matter in the 44 to 52 μeV Range with a Coaxial Dish Antenna". They present the results from a dark photon dark matter search in the mass range from 10.7 - 12.5 GHz using a room-temperature dish antenna setup known as GigaBREAD.
A first data taking run with 24 days of data does not show direct evidence of dark photon dark matter in this mass range. It excludes dark photon photon mixing parameters at 90% confidence level.
Although the researchers did not find dark matter, they were able to narrow the constraints for where it might be. They also demonstrated a unique approach which can speed up the search for the elusive substance at relatively little space and cost.
According to experiment co-leader David Miller, there are many practical advantages to their design, and his team has already shown the best sensitivity to date in the 11-12 gigahertz frequency. They believe that the result is a milestone for their concept, demonstrating for the first time the power of their approach.
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