We report on the first search for atmospheric and for diffuse astrophysical neutrino-induced showers (cascades) in the IceCube detector using 257 days of data collected in the year 2007-2008 with 22 strings active. A total of 14 events with energies above 16TeV remained after event selections in the diffuse analysis, with an expected total background contribution of 8.3±3.6. At 90% confidence we set an upper limit of E2Φ90%CL<3. 6×10-7GeV•cm-2•s-1•sr -1 on the diffuse flux of neutrinos of all flavors in the energy range between 24TeV and 6.6PeV assuming that ΦE-2 and the flavor composition of the νeνμντ flux is 111 at the Earth. The atmospheric neutrino analysis was optimized for lower energies. A total of 12 events were observed with energies above 5TeV. The observed number of events is consistent with the expected background, within the uncertainties.
|Original language||English (US)|
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|State||Published - Oct 3 2011|
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Physics and Astronomy (miscellaneous)