Ultra-High Energy Cosmic Ray Energy Spectrum using Hybrid Analysis with TAx4*

Cosmic rays are subatomic particles of extraterrestrial origin and at the

highest energies, they are not well understood. The variation of the

cosmic ray flux with energy is referred to as the "Energy Spectrum.” The

measurement of the cosmic ray energy spectrum is important because it

may give a hint of where cosmic rays come from. The Telescope Array

(TA) Cosmic Ray Observatory, located in Millard County Utah, is the

largest cosmic ray detector in the Northern hemisphere. Following

evidence for a hotspot in the arrival directions of the highest energy

cosmic rays, TA underwent the TAx4 upgrade to expand the area of

Surface Detectors (SD) by a factor of 4. The upgrade included new

Fluorescence Detector (FD) stations to view over the expanded SD

arrays. In this work, I will present a preliminary cosmic ray energy

spectrum using hybrid events from TAx4, the hybrid resolutions of the

detector, and data-MC comparisons. I will show this work's preliminary

hybrid energy spectrum is in agreement with previous TA

measurements, which is a key first step towards future composition and

anisotropy studies.