Ultra-high-energy cosmic rays


Ultra-high-energy cosmic rays are the highest-energy, rarest charged particles in the Universe. They pack the energy of an aggressively served tennis ball in a single subatomic particle. Their flux at the highest energies is as low as one particle per square kilometer per century! Their sources and their composition remain among the greatest mysteries of high-energy astrophysics. Our group studies ultra-high-energy cosmic rays from both the astrophysics and the particle-physics perspective. We seek to map the magnetic field of the Galaxy, through which these particles propagate, to better understand the paths they follow to reach us, and better gauge where they are coming from. We seek to simulate their interactions in the atmosphere, looking for the possibility that new physical phenomena, yet-unseen in the lab, may appear at these highest-energy collisions known to man. We seek to simulate their propagation through the intergalactic medium, following their path from the - possibly very distant, cosmological - sources to the Earth.

Selected results from our group:

  • Magkos, G. and Pavlidou, V. "Deflections of ultra-high energy cosmic rays by the Milky Way magnetic field: how well can they be corrected?” 2019, JCAP, 02, 004
  • Pavlidou, V. and Tomaras, T.N. "What do the highest-energy cosmic-ray data suggest about possible new physics around 50 TeV?” 2019, PRD, 99, 123016
  • Tritsis, A., Federrath, C. and Pavlidou, V. "Magnetic Field Tomography in Two Clouds toward Ursa Major Using H I Fibers” 2019, ApJ, 873, 38