AMS Experiment Sheds Light on the Flux of Cosmic Rays and Possibly on the Nature of Dark Matter

Understanding cosmic rays is an important part of understanding dark matter. Now, scientists have taken a closer look at these rays, shedding light into the nature of the excess of positrons observed in the flux of cosmic rays.

Cosmic rays are particles that are commonly present in the universe. Consisting mainly of protons and electrons, they can also contain other types of particles that travel through space, including positrons. Positrons are actually the antimatter counterparts of electrons; they have the same mass, but opposite charge. While the presence of some positrons can be explained by the collisions of cosmic rays, this would only produce a tiny portion of the antimatter in the overall cosmic ray spectrum.

In order to better understand cosmic rays and positrons, the researchers mapped the flux of cosmic rays. More specifically, they analyzed 41 billion primary cosmic ray events among which 10 million were identified as electrons and positrons. This provided the scientists with new data at energies never before recorded.

"This is the first experimental observation of the positron fraction maximum after half a century of cosmic rays experiments," said Samuel Ting, AMS spokesperson, the experiment focused on mapping cosmic rays, in a news release. "Measurements are underway by the AMS team to determine the rate of decrease at which the positron fraction falls beyond the turning point."

This rate of decrease is important to physicists who are studying dark matter. In fact, it could be an indicator that the excess of positrons is the signature of dark matter particles annihilating into pairs of electrons and positrons. While the current measurements could be explained by objects such as pulsars, they are also consistent with dark matter particles with mass of the order of 1 TeV.

The findings reveal a bit more about these cosmic rays and may actually help physicists researching dark matter.

"With AMS and the LHC to restart in the near future at energies never reached before, we are living in very exciting times for particle physics as both instruments are pushing boundaries of physics," said Rolf Heuer, CERN director-general.

The findings are published online here and here in Physical Review Letters.