1. Search for Ultra-High Energy Tau Neutrinos in IceCube Dawn Williams University of Alabama For the IceCube Collaboration The 12 th International Workshop on Tau Lepton Physics Nagoya, Japan September 19, 2012 Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

3. Neutrino Astronomy Sources of the highest energy cosmic rays are also potential neutrino sources Large detector required for neutrino astronomy Gamma ray bursts Active galactic nuclei Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

4. The IceCube Detector IceCube construction completed December 2010 86 in-ice strings 60 Digital Optical Modules (DOMs) per string DOMs deployed between 1450 and 2450 m deep Innermost strings form the densely instrumented “DeepCore” array 81 IceTop surface stations 2 tanks per station IceCube data taken during construction 2006-7 data set – IC9 2007-8 data set – IC22 2008-9 data set – IC40 2009-10 data set– IC59 2010-11 data set – IC79 Final configuration, 2011-present – IC86 Location: Amundsen-Scott South Pole Station, Antarctica Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

5. The IceCube DOM ● PMT waveform digitization in-ice ● On-board flasher LEDS for calibration ● Time calibration from surface GPS Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

6. Neutrino Signatures in IceCube Simulated electron neutrino cascade Muon neutrino track (data) Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12 Simulated tau neutrino “double bang”

7. Backgrounds Upgoing events Downgoing events Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

8. UHE Tau Neutrino Background Background UHE tau neutrinos from prompt charm production in atmosphere is negligible in IceCube A.D. Martin, M.G. Ryskin, A.M. Stasto, Acta Phys.Polon.B34:3273-3304,2003 Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

9. Tau Signatures in IceCube ν τ CC interaction τ decay Double Bang Actual appearance in detector depends on tau energy, decay mode and position Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

10. UHE Tau Signatures in IceCube Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

11. Double Pulse For close cascades, a double pulse signature can appear in the digitized waveform Can potentially resolve double bangs down to energies of a few hundred TeV A double pulse waveform from the LED flashers Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

12. Tau Decay to Muons τ μ T. DeYoung, S. Razzaque, D. F. Cowen Astropart.Phys.27:238-243,2007 Tau track is dimmer than muon track of same energy: signature is a track that grows brighter Increase in track brightness Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

13. Partially contained double bangs     Signature is a cascade plus a track or “lollipop” Geometry of the IC22 detector Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

14. Selection Criteria Maximum current ratio IR max = maximum ratio of charge inside sliding time window to charge outside the window Larger for ν τ than for atmospheric muons

15. Selection Criteria Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12 Gray: atm. muon background Blue: all ν τ events Green: lollipop events IR max distributions from simulated events

16. Selection Criteria

17. Effective area in IC22 Cuts have appreciable sensitivity to all flavors of neutrinos Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12 Red: electron Blue: tau Black: muon Dashed – trigger level Solid – analysis level

18. Events that survived final cut Consistent with light from AMANDA module Consistent with neutrino cascade, cannot rule out high energy muon bremsstrahlung energy loss Consistent with horizontal muon in the bottom of the detector Predicted background 0.6 events Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

19. Systematic Errors Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

20. Limits E: all flavor limit from this analysis E*: all flavor sensitivity from this analysis G: IC40 muon neutrino sensitivity x3 WB bound Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12 Published in Phys. Rev. D86, 022005 (2012)

21. PeV-scale Cascades in IC79+86 August 9, 2011 January 3, 2012 2 events in 672 days of IC79+IC86 data 0.14 background events expected from atmospheric conventional+prompt flux Preliminary p-value 0.0094, 2.36σ Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

22. Summary IceCube construction is complete Tau neutrinos are an intriguing potential signature for high energy astrophysical sources Tau neutrino search results published from the construction phase of IceCube PeV-scale cascades observed in IC86 – interesting time for high energy neutrino searches! Dawn Williams University of Alabama Tau Neutrinos in IceCube Tau Lepton Workshop 2012 09/19/12

23. Backup slides

24. IceCube DeepCore 8 strings with densely spaced DOMs higher quantum efficiency Center of IceCube, deepest and clearest ice IceCube is active veto for DeepCore

25. Neutrino Oscillation Muon neutrino disappearance below 30 GeV

26. Tau Appearance ICRC 2011

27. EHE Model Fluxes

28. EHE Cascade Event Rates

29. IC79+IC86 Sensitivity