AMS experiment unveils new territories in the flux of cosmic rays

The Alpha Magnetic Spectrometer (AMS) collaboration presents new insights into the nature of the mysterious excess of positrons observed in the flux of cosmic rays. These are based on the analysis of 41 billion particles, among which 10 million have been identified as electrons and positrons, detected with the space-based AMS detector aboard the International Space Station. 

Since antimatter is extremely rare in the universe, any significant excess of antimatter particles recorded in the flux of energetic cosmic rays indicates the existence of a new source of positrons. 

The distribution of these events in the energy range of 0.5 to 500 GeV shows a well-measured increase of positrons from 8 GeV with no preferred incoming direction in space. The energy at which the positron fraction ceases to increase has been measured to be 275±32 GeV. This rate of decrease after the “cut-off energy” is very important to physicists as it could be an indicator that the excess of positrons is the signature of dark matter particles annihilating into pairs of electrons and positrons.

Although the current measurements could be explained by objects such as pulsars, they are also tantalizingly consistent with dark matter particles with mass of the order of 1 TeV. Therefore, results at higher energies will be of crucial importance in the near future to evaluate if the signal is from dark matter or from a cosmic source.