1. COSMO/CosPA 2010 Searches for the Highest Energy Neutrino with IceCube Searches for the Highest Energy Neutrino with IceCube Aya Ishihara ( Fellow) (JSPS Research Fellow) Chiba University COSMO/CosPA 2010 September 27, 2010

2. IceCube at South Pole 1km 3 volume 80+6 Holes 60 Optical Modules 17 m between modules 125 m between holes construction >90% finished 7 more holes to complete this winter

3. COSMO/CosPA 2010 neutrino muon or tau by track/cascade electron neutrino via cascade Cerenkov light cone Detector Detection Principle

4. Neutrino In the Earth… Generally neutrino identified as “ through the Earth” up- going events Generally neutrino identified as “ through the Earth” up- going events Earth is opaque for EHE neutrino Earth is opaque for EHE neutrino EHE neutrino induced events are coming from above and near horizontal direction EHE neutrino induced events are coming from above and near horizontal direction North down-going up-going  < 1PeV > PeV    EHE CR        EHE neutrino mean free path ~ 100 km << R Earth  cc  ~ 10 -6~-4 mb

5. COSMO/CosPA 2010 The main energy range: E ~ 10 9-10 GeV 2.725 K 411 photons / cm 3 EHE cosmic-ray and CMB induce neutrinos ++ ++  e+e+  e p >1EeV  Diffusive Highest Energy Neutrinos Gorham

6. COSMO/CosPA 2010 Energy Estimation e+e-    pair-creation bremsstrahlung photo-nuclear e+e- 100 TeV  and  tracks loose their energy by radiative processes 9 EeV 

7. COSMO/CosPA 2010 Extremely High Energy Neutrino Signals in IceCube Vertical atmospheric  BG ⇒ Near horizontal signal GZK signal Atmospheric background (CORSIKA)  Soft atmospheric m BG ⇒ Hard signal spectra

8. Basic Information Half IceCube data (2400 optical modules 0.5Km 3 ) Data from 2008/4/17~2009/5/20 Data from 2008/4/17~2009/5/20 Effective live time 370days Effective live time 370days Background MC CORSIKA SIBYLL iron data Background MC CORSIKA SIBYLL iron data Systematic study with proton, QGSJET-II Systematic study with proton, QGSJET-II Blind analysis Blind analysis MC and partial data samples are compared in detail and final selection criteria is determined without looking at full sample MC and partial data samples are compared in detail and final selection criteria is determined without looking at full sample

9. COSMO/CosPA 2010 Data MC comparisons 10% of sample is used for MC applicability 10% of sample is used for MC applicability Energy loss  brightness = NPE Signal is harder than atmospheric muon background

10. COSMO/CosPA 2010 Full Event Distributions on the planes of the final variables log (NPE BTW) shallow SIGNAL shallow BG deep SIGNALdeep BG Cuts are decided without looking at data sample BG 0.11 per full livetime

11. COSMO/CosPA 2010 Null Result…

12. Error Budget Err. SourcesSignal (GZK model) statistical error 0.8 % NPE measurement in-situ calib. -18.5% in-lab calib. 10.1%) +3.89 / -7.22 % neutrino cross section 9.0 % photo-nuclear interaction +10.0 % LPM effect 1.0 % Err. SourcesBackground statistical error 17.0 % Composition-83.86% interaction model+36.1% Coincident event (cos theta>0.2) +29.4% Coincident event (cos theta<0.2) +10.5% ice property+30.2% / - 22.2% NPE measurements +37.1% / -46.7% Signal (GZK1) 0.8 %(stat.) +14.0 -11.6 %(sys.) Background 17.0% (stat.) +60.4 % -96.0%(sys.)

13. COSMO/CosPA 2010 Upperlimit and Sensitivity E -2 flux upperlimit: 10 6.3 < Energy/GeV < 10 9.8 E 2 dN/dE = 4.23 x 10 -8 [GeV cm 2 s -1 sr -1 ] 333.4 days upperlimit with only the half detector IceCube Upperlimit ~2009/5 Full scale sensitivity (MC) Preliminary

14. Expected EHE signal events Models The half IceCube # of events The full IceCube # of events (3 years) GZK1 (Yoshida et al) * 0.573.1 GZK2 Strong Evol. (Sigl) ** 0.91 (C.L 53.4%) 4.9 GZK3 (ESS with W L =0.0) *** 0.291.5 GZK4 (ESS with W L =0.7) *** 0.472.5 GZK5 (Ahlers max) **** 0.89 (C.L 52.8%) 4.8 GZK6 (Ahlers best fit) **** 0.432.3 Z-Burst # 1.03 (C.L 55.7%) 5.1 Top Down(SUSY) ## 5.68 (C.L 99.6%) 31.6 Top Down(QCD) ### 1.19 (C.L 66.4%) 6.3 W&B(evol) ^ 3.724.5 W&B(no evol) ^ 1.15.5 *Yoshida et al The ApJ 479 547-559 (1997), **Kalahsev et al, Phys.Rev.Rev. D 66 063004 (2002), ***Engel et al, Phys. Rev. D, 64(9):093010, 2001, ****Ahlers et al, Astropart. Phys. 34 106-115 (2010) #Yoshida et al, Phys.Rev.Lett. 81 5505 (1998),##Sigl et al, Phys.Rev.Rev. D 59 043504 (1998), ^Razzaque et al(2003)

15. COSMO/CosPA 2010 IceCube’s Wide View in Energy By IceCube 2008-2009

16. COSMO/CosPA 2010 Data MC comparison with the full sample deep BG log (NPE BTW) deep SIGNAL shallow data deep data shallow BG 0.75 < cos theta < 0.8 0.95 < cos theta < 1.0 0.35 < cos theta < 0.4 MC data

17. COSMO/CosPA 2010 The highest NPE event in half IC data >10 PeV muon

18. Summary IceCube is sensitive to neutrino with energies from TeV upto 100EeV IceCube is sensitive to neutrino with energies from TeV upto 100EeV Search 3 flavor neutrinos with energy exceeding PeV Search 3 flavor neutrinos with energy exceeding PeV IceCube from 2008/04 to 2009/05, the half IceCube configuration (~0.5km 3 ) IceCube from 2008/04 to 2009/05, the half IceCube configuration (~0.5km 3 ) Null results has set the world’s best 3 flavor upperlimit to date from 10 6 to 10 10 GeV Null results has set the world’s best 3 flavor upperlimit to date from 10 6 to 10 10 GeV Can constrain to hadronic component of the extragaractic Universe Can constrain to hadronic component of the extragaractic Universe

19. COSMO/CosPA 2010 Diffusive High Energy Lights    e e+e+  Extragaractic-diffuse  VHE p  What’s making the extragaractic Universe so bright? unknown IR/UV background Fermi LAT

20. COSMO/CosPA 2010 USA: Bartol Research Institute, Delaware University of California, Berkeley University of California, Irvine Pennsylvania State University Clark-Atlanta University Ohio State University Georgia Tech University of Maryland University of Alabama, Tuscaloosa University of Wisconsin-Madison University of Wisconsin-River Falls Lawrence Berkeley National Lab. University of Kansas Southern University and A&M College, Baton Rouge University of Alaska, Anchorage Sweden: Uppsala Universitet Stockholm Universitet UK: Oxford University Belgium: Université Libre de Bruxelles Vrije Universiteit Brussel Universiteit Gent Université de Mons-Hainaut Germany: DESY-Zeuthen Universität Mainz Universität Dortmund Universität Wuppertal Humboldt Universität MPI Heidelberg RWTH Aachen Japan: Chiba University New Zealand: University of Canterbury 33 institutions, ~250 members http://icecube.wisc.edu Switzerland: EPFL The IceCube Collaboration

21. COSMO/CosPA 2010 Different Windows to the high energy neutrinos Optimized for <10 6 GeV neutrinos Optimized for >10 6 GeV neutrinos (This Talk)

22. Signal Event Distributions x = E 2 dN/dE Exposure/E IC40

23. COSMO/CosPA 2010 Agreement between Data/MC with full data sample shallow

24. COSMO/CosPA 2010