Highlights from Telescope Array

TL;DR

This paper reviews three years of Telescope Array observations, detailing the energy spectrum, composition, and arrival directions of ultra-high energy cosmic rays, highlighting key spectral features and the dominance of protons above 10^18.2 eV.

Contribution

It provides the first detailed analysis of the energy spectrum, composition, and anisotropy of cosmic rays above 10^18 eV using hybrid detection methods.

Findings

Ankle feature at 10^18.7 eV identified.

Spectral index changes from -2.68 to -4.2 at the second bending point.

Protons dominate cosmic rays above 10^18.2 eV.

Abstract

The results from the first three years observation in Telescope Array are reviewed. The energy spectrum, mass composition, and anisotropy in arrival directions of ultra-high energy cosmic rays are discussed. The energy spectrum of cosmic rays with energies above $10^{18}$ eV is determined using the data of the fluorescence detectors, surface detectors, and with a hybrid shower reconstruction technique using the both data. The ankle structure is clearly found at $10^{18.7}$ eV. The second bending point is also identified, at which the flux of cosmic rays begins to decrease and the spectral index changes from $E^{-2.68}$ to $E^{-4.2}$. The study of shower development using the fluorescence detector data shows that proton is dominant in cosmic rays above $10^{18.2}$ eV. No apparent anisotropies in the arrival direction of cosmic rays are found. I also present further experimental extensions which are being developed at the Telescope Array site.