We analyze Galactic cosmic rays, for which data is provided by space-based experiments with increasing precision.Topics of interest
- Galactic cosmic ray propagation
- Indirect dark matter searches with antimatter in cosmic rays (positrons, antideuterons, antiprotons)
- Interpretation of high energy e+ and e- fluxes
- Cross sections uncertainties for cosmic rays predictions
About Cosmic rays
Cosmic rays are charged particles which fill our Galaxy. Their energy ranges from MeVs (106 eV) to EeVs (1018 eV) thus spanning 12 orders of magnitude. The flux of these cosmic rays follows a steeply falling power-law in energy with in index between -2.7 and -3.1. At the highest energies our Galaxy is no longer capable to trap the cosmic rays in its magnetic field. Therefore, naturally a separation between galactic and extragalactic cosmic rays is at hand. The exact transition between the two regimes is still under discussion, however, it might be connected with the two breaks observed in the cosmic-ray energy spectrum, commonly known as knee and ankle.
We are mainly interested in Galactic cosmic rays, which are currently measured with ever increasing precision by space-based detectors. The journey started with the PAMELA experiment onboard of the Resurs-DK1 satellite and is nowadays continued by the AMS-02 experiment born to the International Space Station. These detectors determine the energy spectrum of the individual cosmic ray species in an energy range from 1 GeV to a few TeV. The cosmic-ray fluxes are dominated by protons and helium at roughly 90% and 10%, respectively. At and below the percent level we observe heavier nuclei as well as electrons, positrons, and antiprotons. We analyze all the data to draw conclusions about the propagation and sources of cosmic rays. Next to standard astrophysical sources like supernova remnants or pulsars also dark matter is a viable source candidate. One important goal is to use cosmic ray data to search or constrain dark matter.
Cosmic-ray propagation is described by a diffusion equation. To our current understanding they are accelerated at thermal shock fronts as expected in the vicinity of supernova remnants or pulsars. After injection they take a random walk in the magnetic fields of our Galaxy, where they might be reaccelerated by scattering of Alfven magnetic waves or driven away from the Galactic plane by convective winds. Electrons and positrons are effected by energy loss processes due to ionization or synchrotron radiation. Furthermore, they might produce so called secondaries by fragmentation or decay. The secondary-to-primary ratios carry valuable information about the propagation effects in the Galaxy and are therefor of special interest. Finally, rare secondaries like antiprotons, positrons, or antideuteron are fascinating species, since they might contain valuable (indirect) information about dark matter.