Thursday, May 10, 2012
3:00pm (206 JFB)
Title: Monocular Measurement of the Ultra High Energy Cosmic Ray Spectrum while Relaxing the Profile Constraint
Cosmic rays are charged particles of galactic and extragalactic origin. In the ultra high energy regime, due to their extremely low flux, cosmic rays can only be observed indirectly via an extensive air shower induced when they interact in the Earth's atmosphere. The Telescope Array (TA) experiment, the largest experiment in operation in the northern hemisphere, observes the longitudinal profile of the fluorescence light from these extensive air showers via telescopes. The Middle Drum fluorescence telescope station utilizes the same equipment as the HiRes-I site of the High Resolution Fly's Eye (predecessor to Telescope Array) experiment. The equipment has simply been reconfigured. As HiRes-I, the telescopes viewed 3-17o in elevation and nearly 360o in azimuth. As a result of this, the track length in the cameras tended to be short. In the Telescope Array configuration, the telescopes view 3-31o in elevation, but only about 120o in azimuth, however, the resulting track lengths are significantly longer. With the short track lengths, one needed to make an assumption about the shape of the profile; that it had a Gaisser-Hillas shape. The longer track lengths make this unnecessary. I have analyzed the data using a Time vs Angle geometry method. The results show an ultra high energy cosmic ray energy spectrum that is consistent with the previous results of the HiRes experiment as well as that measured by the TA surface detectors.