In a new paper in Nature, IceCube shows a solid, non-detection of neutrinos from gamma-ray bursts (GRBs). That is, the expected emission of neutrinos if GRBs were the sources of the highest energy cosmic rays was not observed. There had been a generally agreed model of GRB emission, and now it’s essentially ruled out. Cosmic rays remain a mystery…
More personal comments on this in a bit, but let me send along some of the news coverage in the shorter term:
IceCube popular version of the Mystery of the Cosmic Rays
“Although we have not discovered where cosmic rays come from, we have taken a major step towards ruling out one of the leading predictions,” said IceCube principal investigator and University of Wisconsin-Madison physics professor Francis Halzen.