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%.
Methodology
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%.
Link to original