EHE Search for EHE neutrinos with the IceCube detector Aya Ishihara Chiba University

EHE Neutrino Underground Fluxes at the IceCube depth S. Yoshida et. al. (2004) Phys. Rev. D main signal GZK neutrino induced leptons background Atmospheric muon Simple energy cut works! atmospheric muon flux above 10 6 GeV is very uncertain Surface fluxes atm  Target GZK neutrino Surface energy range 8 < Log(E/GeV) < 12 (energy at depth ~ 6-7 < Log(E/GeV) < 10-11) E GZK >> E Atm 

Energy ! e+e-    pair-creation bremsstrahlung photo-nuclear e+e- 100 TeV  and  tracks loose their energy by radiative processes 9 EeV  ?

The 9-string real sample 2006 Example Bright Events NPE = integral of waveforms / single charge 20mV 0mV [ns] digital optical module waveform

Visible Energy vs. NPE correlation up to log 10 NPE ~ 4.5 then, early saturation effect diffuse them NPE and Energy Correlation with 2006 IceCube configuration   log (  Energy / GeV ) log (  Energy / GeV )

6 log Cosmic-Ray Energy Number of muon in a shower above threshold Energy E thres (Elbert parameterization) This relation - CR energy and energy contributes to muons in shower and CR flux intensity gives atmospheric  bundle flux Nagano, Watson: Reviews of Modern Physics Vol 72 No3 (689)   Atmospheric Muon Bundles Model

7 Background simulation experimental data atmospheric  simulation model 1 atmospheric  simulation model 2 cos  log 10 NPE 4 < log 10 NPE < 5

8 Atmospheric fluxes at IceCube depth Model  E thres [GeV] with GZK cutoff !! #1 #2 without GZK cutoff #1

9 Comparison with CORSIKA Atmospheric  empirical model Proton QGSJET01 Iron QGSJET01 log (Primary CR Energy [GeV]) log (  Bundle Energy at Depth [GeV]) log (Primary CR Energy [GeV]) underestimateoverestimate  bundle energy 1 PeV  bundle energy 100 TeV 10 PeV

Event Selection and Numbers Cut Level GZK events e     Atmospheric  model 1 Atmospheric  model 2 1 (dotted brown) (solid red)0.046< (dotted black)0.036< (solid brown)0.024< 10 -4

11 Sensitivity for 2006 all  flavor added assuming 1:1:1 90 % C.L.    cut2    [GeV cm -2 sr -1 sec -1 ]

Neutrino Effective Area Cut 2

Summary The IceCube 9 string array provided physics data sample in 2006 MC shows 9 string IceCube is capable of EHE neutrino search but early saturation and reduced bin numbers limits its capability For BG estimation, Related EHE CR fluxes and surface  bundle energy relation from experimental sample expressed in terms of Elbert formula The obtained empirical model gives good agreement with data Cut candidates are selected according to the model Effective area, sensitivity for 2006 IceCube EHE region is obtained