February 17

Karen Andeen (Rutgers)

First Measurement of Cosmic Ray Composition using the IceCube Neutrino Observatory

The recently completed IceCube Neutrino Observatory instruments a volume of roughly one cubic kilometer (one gigaton) of Antarctic ice with more than 5000 digital optical modules.  While IceCube was primarily designed to detect high energy neutrinos, the overwhelming majority of events are caused by downing cosmic-ray induced muons. These muons, when measured in coincidence with events from the IceTop air shower array on the surface of the icecap, provide an indirect measurement of the cosmic ray primary particle, mediated by the physics of air shower propagation. These measurements can be used to acquire the cosmic ray energy spectrum and composition at energies near and above the "knee"--a critical feature in the spectrum where the spectral index steepens. The results of the first coincident analysis from IceCube and IceTop will be discussed.