The IceCube Neutrino Observatory Part II: Atmospheric and Diffuse UHE Neutrino Searches of All Flavors

IceCube, a cubic kilometer detector at the South Pole, is the largest neutrino telescope currently taking data. Utilizing the transparent ice of Antarctica as a detection medium, IceCube digital optical sensors observe Cherenkov radiation from secondary particles produced in neutrino interactions inside or near the detector. Charged current nμ interactions create muon tracks, while charged current ne interactions, and neutral current interactions of all flavors initiate electromagnetic and hadronic showers (cascades). The background coming from atmospheric muons and muon bundles is many orders of magnitude larger than the cascade signal and makes it difficult to observe cascades. However, cascades have better energy resolution and lower atmospheric neutrino background compared to track-like events. The energy spectrum of extraterrestrial neutrinos is expected to be harder than that of atmospheric neutrinos. Thus using cascade events to search for a hardening of the energy spectrum is advantageous compared to using muon tracks. The search for extraterrestrial neutrino-induced cascades with energies in the tens of TeV to a few PeV neutrino energy range using improved reconstruction methods will be presented. The analysis uses 317 days of livetime of the data taken from May 2010 to May 2011 when 79 IceCube strings were operational. Corresponding authors: Mariola Lesiak-Bzdak2 and Achim Stößl3 2 Department of Physics and Astronomy, Stony Brook University. Stony Brook, NY 11794-3800 3 DESY, Platanenallee 6, 15738 Zeuthen, Germany