Astroparticle Seminar

Showers in the desert:
measuring ultra-high-energy cosmic rays with Telescope Array

Thomas Stroman

University of Utah

Cosmic rays with ultra-high energy (above 1 EeV) are extremely rare. Experimental investigation of their properties requires enormous detectors, of which Telescope Array (TA) is the northern hemisphere's largest. Operating in west-central Utah since 2007, TA employs a combination of hundreds of surface detectors and dozens of ultraviolet telescopes to observe the extensive air showers produced by cosmic-ray interactions with the atmosphere. I will describe the instrumentation, data acquisition, analysis, and simulation procedures used by TA to reconstruct the primary energy, final trajectory, and air-shower evolution of each measured cosmic ray, and what the aggregate data reveal about the energy spectrum, chemical composition, and source distribution of ultra-high-energy cosmic rays, including our recently published detection of a localized “hotspot” responsible for more than a quarter of all cosmic rays observed by TA with E > 57 EeV. I will also describe present and future operations to expand TA, extend its detection threshold to energies below 10 PeV, and explore new methods and phenomena related to cosmic-ray detection.