On MeV Gamma Rays Accompanying High Energy Cosmic Neutrinos

Prof. Francis Halzen

Wisconsin IceCube Particle Astrophysics Center and University of Wisconsin-Madison

High-energy neutrinos originate in astrophysical beam dumps where accelerated cosmic rays interact with radiation, hydrogen and molecular clouds with sufficient target density to produce charged pions that decay into neutrinos. These are inevitably accompanied by photons from the decay of neutral pions. In the most powerful neutrino sources, these photons will lose energy in the source before, additionally, losing energy by propagation in the EBL. The 2014-15 neutrino burst of TXS 0505+056 provides an observation where the accompanying photons reach Earth with energies below the threshold of the Fermi satellite. We will discuss classes of neutrino sources with sufficient target density to produce high-energy neutrinos and shift the accompanying gamma ray flux to MeV energies and below.