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

2. EHE Neutrino Underground Fluxes at the IceCube depth S. Yoshida et. al. (2004) Phys. Rev. D 69 103004 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 

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

4. The 9-string real sample 2006 Example Bright Events NPE = integral of waveforms / single charge 20mV 0mV [ns] Digital optical module waveform (ATWD / FADC)

5. Visible Energy vs. NPE correlation up to log 10 NPE ~ 4.5 the resolution is then diffused by waveform saturation effects NPE and Energy Correlation with 2006 IceCube configuration   log (  Energy / GeV ) log (  Energy / GeV )

6. 6 log Cosmic-Ray Energy Number of muon in a shower above threshold Energy E thres (Elbert parameterization) This relation between cosmic ray energies and the energy of the muon bundle fixes atmospheric muon bundle fluxes Nagano, Watson: Reviews of Modern Physics Vol 72 No3 (689)  Atmospheric Muon Bundles Model

7. 7 Background simulation Partial experimental data atmospheric  simulation model 1 atmospheric  simulation model 2 cos  log 10 NPE 4 < log 10 NPE < 5 Model  E thres [GeV] 11.9300 22.0 1500

8. 8 Atmospheric fluxes at IceCube depth Model  E thres [GeV] 11.9300 22.0 1500 with GZK cutoff !! #1 #2 without GZK cutoff #1

9. 9 Comparison with CORSIKA Atmospheric  empirical model Corskia Proton QGSJET01 Corsika Iron QGSJET01 log (Primary CR Energy [GeV]) log (  Bundle Energy at Depth [GeV]) log (Primary CR Energy [GeV]) overestimate  bundle energy 1 PeV  bundle energy 100 TeV  bundle energy 10 PeV underestimate proton and ion both underestimate the rate

10. Event Selection and Numbers Cut Level GZK events e     Atmospheric  model 1 Atmospheric  model 2 1 (dotted brown)0.0550.0030.006 2 (solid red)0.046< 10 -4 3 (dotted black)0.036< 10 -4 4 (solid brown)0.024< 10 -4 GZK  GZK  Atm.  number of events

11. 11 Sensitivity for 2006 all  flavors added assuming 1:1:1 ratio 90 % C.L.    cut2  10 6.5  10 9.5  10 -6 [GeV cm -2 sr -1 sec -1 ]

12. Neutrino Effective Area average over full solid angle Cut level 2

13. Summary The IceCube 9 string array provided physics data sample in 2006 MC shows 9 string IceCube is capable of EHE neutrino search but waveform saturation and its readout limits its capability For BG estimation, Elbert formula, derived from experimental relation between EHE CR fluxes and surface mu bundle energy, used Effective area, sensitivity of ~10 -6 [GeV cm -2 sr -1 sec -1 ] for 2006 IceCube EHE region is obtained with optimized cuts with the assumption of zero background events from the empirical atmospheric  background model

14. 14 backup

15. 15 Comparison with CORSIKA Proton QGSJET01 Iron QGSJET01

16. The 9-string real sample 2006 FADC Waveforms saturated

17. 17 NPE EHE waveforms Integrating a waveform/single charge = NPE = + 4.5V 0V 20mV 0mV high gain low gain 4.5V 0V 120mV 0mV