Enlarge / AMS aboard the International Space Station. (credit: NASA)
What happens when two dark matter particles collide? We don’t know the answer to that question because we don’t know what dark matter is. A whole host of possible particles could constitute dark matter, and some of them allow dark matter to “self-interact.” Here, when two dark matter particles collide, they would decay into other particles that we could potentially observe. This should happen often in regions of the Universe densely populated with dark matter, and it’s possible that some of the resulting particles are bombarding us all the time—we just don’t know their origin.
Our atmosphere is constantly bombarded by particles from space of varying kinds, collectively known as cosmic rays. Cosmic rays come from sources such as supernovae and active galactic nuclei (exceptionally bright cores of galaxies). Could some of them also come from collisions of dark matter particles? Sorting that one out has been challenging.
The Alpha Magnetic Spectrometer (AMS-02) aboard the International Space Station has recently provided new data on the flux of antiprotons reaching the Earth’s atmosphere. (antiprotons are the antiparticles of protons). Because of the unprecedented precision of that data, two new teams have separately published papers, without knowledge of each other, using the new data to make an argument that some of the antiprotons are being produced in dark matter particle collisions.
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