O-10 - Telescope Array SD spectrum shows an ankle at 4.6e18 eV and a 5.5-sigma flux suppression at 5.4e19 eV
Spectral indices: -3.34 +/- 0.04 (below ankle), -2.67 +/- 0.03 (between breaks), -4.6 +/- 0.6 (above suppression). Dominant systematic: 22% energy-scale uncertainty (SD scale fixed to the calorimetric fluorescence-detector scale via a 27% renormalization from FD-SD common events), propagating to 37% in flux; aperture systematic ~3%.
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Telescope Array surface detector (scintillator ground array, Utah, Northern Hemisphere): 4 years of data (May 2008 - May 2012), 13,100 events above 10^18.2 eV, exposure 3690 km^2 sr yr. The SD energy scale is fixed to the calorimetric fluorescence-detector scale via a 27% renormalization derived from FD-SD common events. Dominant systematic: 22% energy-scale uncertainty, propagating to 37% in flux; aperture systematic ~3%.
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Why this is evidence
H-9 predicts exactly this ankle-plus-suppression pair from proton propagation losses on the CMB (and TA’s E_1/2 lands at the GZK-predicted value); H-12 also predicts a steepening but as a source rigidity cutoff, not tied to the GZK scale; the instrumental-artifact branch of H-37 predicts no robust break at all. The suppression’s existence and its energy pull these apart.