33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013 THE ASTROPARTICLE PHYSICS CONFERENCE The Hybrid Energy Spectrum and Composition of Telescope Array’s Middle Drum

Abstract: The Telescope Array experiment (TA) studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated by a primary cosmic ray particle, while scintillation detectors measure the lateral distribution of secondary particles that hit the ground. The Middle Drum (MD) fluorescence telescope consists of 14 telescopes from the High Resolution Fly’s Eye experiment (HiRes), providing a direct link back to the HiRes data and measurements. Using the scintillation detector data in conjunction with the MD data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. In addition, the constraint of the core location by the surface array allows us to make a more precise measurement of the composition of the primary cosmic rays. The Middle Drum hybrid results are presented