Phys. Rev. Lett. 101, 221101 (2008) [5 pages]Discovery of Localized Regions of Excess 10-TeV Cosmic Rays
See accompanying Physics Viewpoint The 7 year data set of the Milagro TeV observatory contains 2.2×1011 events of which most are due to hadronic cosmic rays. These data are searched for evidence of intermediate scale structure. Excess emission on angular scales of ∼10° has been found in two localized regions of unknown origin with greater than 12σ significance. Both regions are inconsistent with pure gamma-ray emission with high confidence. One of the regions has a different energy spectrum than the isotropic cosmic-ray flux at a level of 4.6σ, and it is consistent with hard spectrum protons with an exponential cutoff, with the most significant excess at ∼10 TeV. Potential causes of these excesses are explored, but no compelling explanations are found. © 2008 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.101.221101
DOI:
10.1103/PhysRevLett.101.221101
PACS:
95.85.Ry, 96.50.Xy, 98.35.Eg, 98.70.Sa
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