Ultra-high energy cosmic rays and neutrinos from gamma-ray bursts: revising the predictions and clarifying the connection
by
DrMauricio Bustamante(Julius-Maximilians Universität Würzburg)
→
Europe/Stockholm
Å12167 (Uppsala University)
Å12167
Uppsala University
Description
For the past fifty years we have been detecting ultra-high energy cosmic rays (UHECRs); with energies above 10^18 GeV, they are the most energetic particles yet observed. Their origin, however, remains unknown, though gamma-ray bursts (GRBs) are arguably among the most prominent potential sources: their high luminosity (> 10^52 erg s^-1) hints at the possibility that the same processes that create the gamma-rays are also responsible for creating the UHECRs (protons) by means of shock-accelerating them in intense magnetic fields. The smoking gun of such a connection would be the detection of UHE neutrinos of comparable energy produced in the same proton-photon interactions in the sources. Presently, the increased sensitivity of the current km-scale neutrino telescopes has started to strongly constrain the analytical models of astrophysical UHE neutrino production which we have been using for the past fifteen years, and to put tension on the hypothesis of GRBs as possible sources of UHE neutrinos. We show that this tension can be alleviated by using instead a revised numerical prediction of the neutrino flux (NeuCosmA) which yields an expected neutrino flux that lies still comfortably one order of magnitude below the current upper bounds. Furthermore, we introduce a generalised model of UHECR emission from GRBs, where the magnetic confinement of the protons in the source is imperfect and some of them are able to "leak out" of the source before having interacted, thus affecting both the UHECR and neutrino fluxes. Finally, I will touch upon the cosmic ray-neutrino connection and argue that the current UHECR observations and the bounds on the UHE neutrino flux might already be enough to put tension on several possibilities of particle emission and propagation, and to point us towards some requirements that should be fulfilled by GRBs.
