| Description |
Evidence of a number of interrelated energy dependent intermediate-scale anisotropies have been found in the arrival directions of proton-like ultra-high energy cosmic rays (UHECR) using 7 years of Telescope Array (TA) data. These are found using analysis techniques that have been developed for this dissertation. Using surface detector (SD) data the reported TA "Hotspot" excess, E#21;1019.75 eV, is found to correspond to a deficit, or "Coldspot," of events for 1019.1#20;E<1019.75 eV at 142#14; R.A., 40#14; Dec. The global posttrial significance of this Hot/Coldspot event density asymmetry is found to be 5.1s (p = 1.56 #2; 10.7). This Hot/Coldspot feature is the combination, at the same location, of an energy spectrum anisotropy with a 3.74s significance for energies E#21;1019.2 eV and an energy-distance correlation with a 3.34s significance for energies E#21;1019.3 eV. The UHECR Hotspot alone is analyzed using a new kernel density estimation (KDE) anisotropy method and found to have a 3.65s significance (E#21;1019.75 eV). These features suggest energy dependent magnetic deflection of UHECR. The composition of UHECR primary particles is also studied using a new "Quality Factor Analysis" pattern recognition event selection for fluorescence detectors (FD). This minimizes the energy dependence of the resolution of extensive air shower (EAS) Xmax depth. Also, a new statistical method making use of all higher moments than the mean hXmaxi shower depth distribution is developed - as there is large disagreement in hXmaxi between all EAS simulation models. There is also an uncertainty, just as large, for any particular model, given uncertainties in particle interaction parameters extrapolated to much higher energies from Large Hadron Collider (LHC) data. The TA hybrid FD/SD data is found to be statistically compatible with a pure proton composition, though not incompatible with a light mixed composition, for all models of EAS above E#21;1018.4 eV. There is also no statistically significant evidence of the composition getting heavier at the highest energies. The combined information of a proton-like light composition, and anisotropy evidence suggestive of energy dependent magnetic deflection of UHECR, should be useful for informing future source searches and models of intergalactic propagation through magnetic fields. |
