1. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 1 Beyond IceCube @ the South Pole Outline  Introduction: Optical vs. Radio & Acoustic  Moving to the GZK scale: E > 10 16 eV sensitivities  Radio ● RICE ● Near-term future ideas  ROCSTAR/DRM  Surface array  Acoustic ● Near-term future ideas  SPATS  Capabilities of a combined IceCube, Radio and Acoustic (IRA) detector  Comments on IRA  sensitivities  Conclusions

2. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 2 Optical vs. Radio & Acoustic  IceCube has been optimized for energies in the range between roughly 1 TeV and 10 PeV  The buried array relies on one type of detection channel: optical ● Cherenkov light from UHE -induced charged particles  att ~ 30m requires high module density – IceCube has  ~5000/km 3 ● To get sufficient statistics at higher energy scales (e.g., GZK scale), where one needs a fiducial volume closer to 100-1000 km 3, need technology that is practical at lower module densities

3. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 3 Optical vs. Radio & Acoustic  Happily, ice is also well-suited for detection of UHE neutrino-induced radio and acoustic signals ● Cherenkov radio signals  ~1km attenuation length  proven technology (RICE) ● Acoustic signals  ~10km attenuation length  potentially very quiet environment (vs., e.g., ocean)  Coincident event capture offers many benefits ● Therefore, in this talk we will focus on efforts using ice at the South Pole ● Will not cover other very interesting and promising radio and acoustic efforts, like ANITA, SalSA, SAUND,…

4. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 4 Beyond IceCube @ the South Pole Outline  Introduction: Optical vs. Radio & Acoustic  Moving to the GZK scale: E > 10 16 eV sensitivities  Radio ● RICE ● Near-term future ideas  ROCSTAR/DRM  Surface array  Acoustic ● Near-term future ideas  SPATS  Capabilities of a combined IceCube, Radio and Acoustic (IRA) detector  Comments on IRA  sensitivities  Conclusions

5. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 5 Focus on “Guaranteed” UHE Neutrinos  GZK flux models From Gorham et al., Phys. Rev. D72 (2005) 023002 ● Roughly speaking, depending on various assumptions, to detect one GZK /yr at 10 16-19 eV requires V eff ~ 4-50 km 3  See, e.g., Engel, Seckel and Stanev, Phys. Rev. D64 (2001) 093010

6. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 6 Discovery Aperture vs. E Saltzberg, astro/ph 0501364

7. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 7 Beyond IceCube @ the South Pole Outline  Introduction: Optical vs. Radio & Acoustic  Moving to the GZK scale: E > 10 16 eV sensitivities  Radio ● RICE ● Near-term future ideas  ROCSTAR/DRM  Surface array  Acoustic ● Near-term future ideas  SPATS  Capabilities of a combined IceCube, Radio and Acoustic (IRA) detector  Comments on IRA  sensitivities  Conclusions

8. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 8 UHE Neutrino Radio Detection: RICE  Design ● 20-channel array of dipole antennas ● 100-300m depths ● 200x200x200 m 3 deployment volume ● Analog readout into surface digitizers 5 m 10 cm

9. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 9 UHE Neutrino Radio Detection: RICE  Results (Kravchenko et al., astro-ph/0601148) ● 1999-2005 RICE livetime of ~20500 hrs (V eff ×livetime ~ 1-10 km 3 ۰yr۰sr @ 10 17-19 eV) ● (Results from GLUE, ANITA, FORTE in the literature & at this workshop)

10. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 10 Beyond IceCube @ the South Pole Outline  Introduction: Optical vs. Radio & Acoustic  Moving to the GZK scale: E > 10 16 eV sensitivities  Radio ● RICE ● Near-term future ideas  ROCSTAR/DRM  Surface array  Acoustic ● Near-term future ideas  SPATS  Capabilities of a combined IceCube, Radio and Acoustic (IRA) detector  Comments on IRA  sensitivities  Conclusions

11. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 11 New Ideas for Radio at the South Pole  “ROCSTAR” ● Retrofitted OptiCal SysTem Adapted for Radio ● Piggybacks on existing IceCube DOMs  Use Main Board as-is for timing and power  Replace “flasher board” with radio digitizer board to process all radio-related signals – use pre-existing interface bus to MB  Remove PMT, HV stuff, etc.  Rename it “DRM” for Digital Radio Module

12. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 12 Possible ROCSTAR Node Configuration ≈50m

13. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 13 Possible ROCSTAR Block Diagram AntennasAntennas Local coincidence triggering

14. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 14 ROCSTAR Deployment Depth  Optical-Radio coincident event rate can be substantial  Preferable to deploy close to surface, but temperature still reasonably cold (-42C) at 1450 m  Simulations needed to optimize geometry ROCSTAR Nodes (~70)

15. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 15 ROCSTAR  Advantages ● Uses existing hardware with minimal modification to significantly enlarge radio array at the South Pole ● Straightforward to integrate into existing optical array data acquisition system to make functioning hybrid detector and see coincident events ● Minimal impact on IceCube deployments  Disadvantages ● Geometry somewhat inflexible, not optimal ● Use of existing hardware imposes some constraints on design of in-ice radio electronics (probably not severe)

16. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 16 Beyond IceCube @ the South Pole Outline  Introduction: Optical vs. Radio & Acoustic  Moving to the GZK scale: E > 10 16 eV sensitivities  Radio ● RICE ● Near-term future ideas  ROCSTAR/DRM  Surface array  Acoustic ● Near-term future ideas  SPATS  Capabilities of a combined IceCube, Radio and Acoustic (IRA) detector  Comments on IRA  sensitivities  Conclusions

17. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 17 Surface Array  Calibration of UHE neutrino detectors is tricky due to lack of a “test beam” ● IceCube approach  in-situ light sources (LEDs, lasers) to mimic cascade events up to ~50 PeV  cosmic-ray muons and atmospheric  -induced muons up to about 10 TeV ● Radio and Acoustic approaches  in-situ (or nearby) transmitters  New idea (Seckel & Seunarine) ● use Askaryan radio pulse produced when cosmic-ray air shower core’s particles hit the earth (or the ice upon it)  comprise a few % of the energy of the air shower

18. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 18 Surface Array  Use an array of radio antennas near the surface at the Pole  Trigger with IceTop, the air shower array atop the IceCube buried array  With E p >3PeV, a 30 m × 30 m array would see ~1 ev/hr  Not just for radio array calibration ● cosmic-ray composition studies may be possible too  RICE might be able to do this  More simulation work needed

19. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 19 Beyond IceCube @ the South Pole Outline  Introduction: Optical vs. Radio & Acoustic  Moving to the GZK scale: E > 10 16 eV sensitivities  Radio ● RICE ● Near-term future ideas  ROCSTAR/DRM  Surface array  Acoustic ● Near-term future ideas  SPATS  Capabilities of a combined IceCube, Radio and Acoustic (IRA) detector  Comments on IRA  sensitivities  Conclusions

20. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 20 UHE Neutrino-Induced Acoustic Signals  A -induced cascade will produce localized heating in the medium, creating a pressure wave  Detect sound, peaked at ~40kHz, with detectors distributed in the ice at the South Pole  Short-term issues: ● absorption length  probably large; must measure ● refraction ● background noise  probably small; must measure – man-made on surface – slip-stick of glacier on bedrock – micro cracks  N.B.: No noise from dolpins, ships, wind, waves,… S. Boeser/DESY

21. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 21 UHE Neutrino-Induced Acoustic Signals  Predicted attenuation length for sound in ice looks very promising (plot below is for 10kHz): Depth variation is due to change in temperature of the ice at Pole. J. Vandenbroucke/ARENA 2005

22. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 22 Acoustic Detection Contours in Ice Contours for P thr = 9 mPa: raw discriminator, no filter J. Vandenbroucke/ARENA 2005 longitudinal coord. lateral coord.

23. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 23 Acoustic Signals: SPATS South Pole Acoustic Test System  Purpose: measure ● noise ● refraction ● attenuation length  Design for 06/07 season ● Deploy in 3 IceCube holes at 400m depth ● 7 acoustic stages per hole  sensor and transmitter ● 3 surface interface boxes  power, network interface ● 1 master CPU  network interface, GPS timestamp

24. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 24 SPATS Module Modules at DESY/Zeuthen Sensor ModuleOne Full Module

25. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 25 After SPATS…  If the measurements made with SPATS during the 2006/2007 season at the South Pole are encouraging, the next step will be to plan and hopefully build a much larger device ● ~100 km 3 effective volume at GZK energies ● ~100 strings on 1 km spacing grid ● ~300 receivers per string (co-deployed with radio)

26. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 26 Beyond IceCube @ the South Pole Outline  Introduction: Optical vs. Radio & Acoustic  Moving to the GZK scale: E > 10 16 eV sensitivities  Radio ● RICE ● Near-term future ideas  ROCSTAR/DRM  Surface array  Acoustic ● Near-term future ideas  SPATS  Capabilities of a combined IceCube, Radio and Acoustic (IRA) detector  Comments on IRA  sensitivities  Conclusions

27. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 27 Hybrid “IRA” Detector  As in HEP and Auger, using more than one detection technique to view the same fiducial volume is highly advantageous ● Detecting events in coincidence between 2-3 methods is more convincing than detections with 1 method alone ● Coincident events allow calibration/cross-checks one method relative to the others ● Hybrid reconstruction will give superior energy and direction resolution than with one method, or at least will allow reconstruction of coincident events that cannot be reconstructed with one method alone  Good complementarity ● Overlapping sensitivities in energies around 10-100PeV  At lower energies, optical device is better  At higher energies, radio/acoustic are better  The resulting hybrid detector would have sensitivity to neutrinos over about 10 orders of magnitude in energy! Halzen & Hooper “IceCube Plus” JCAP 01 (2004) 002

28. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 28 Hybrid IceCube+Radio+Acoustic  Simulations* have been made of a hybrid detector consisting of ● IceCube plus 13 “outrigger” strings (×) ● 91 additional radio/acoustic holes with 1 km spacing (o)  5 radio receivers 200-600 m  300 acoustic receivers, 5- 1500 m  2  acceptance, hadronic shower only (LPM stretches EM showers), E sh = 0.2E *See D. Besson et al., ICRC 2005

29. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 29 Hybrid IRA Simulation  Result: ● V eff at E>10 17 eV increased by a factor of 5-25 over IceCube alone (V eff > ~100km 3 ) ● ~20 GZK events/year  Notes: ● ESS flux, Gandhi  ’s,   = 0.7 ● For R, A, R+A  all flavors  NC and CC ● For O**  only  I=IceCube R=Radio A=Acoustic (GZK ’s/yr) V eff (km 3 ) Log 10 [E /eV]

30. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 30 Some Comments on UHE  with IRA  High energy tau neutrinos are especially good candidates for coincident event capture; V eff increases by a lot ● Double bangs  one bang in radio/acoustic array, one in optical array ● Lollipops  detect tau lepton track in optical array, tau decay cascade in radio/acoustic array ● Sugardaddies (see talk by T. DeYoung)  detect tau lepton creation in radio/acoustic, tau decay to muon in optical array

31. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 31 Beyond IceCube @ the South Pole Outline  Introduction: Optical vs. Radio & Acoustic  Moving to the GZK scale: E > 10 16 eV sensitivities  Radio ● RICE ● Near-term future ideas  ROCSTAR/DRM  Surface array  Acoustic ● Near-term future ideas  SPATS  Capabilities of a combined IceCube, Radio and Acoustic (IRA) detector  Comments on IRA  sensitivities  Conclusions

32. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 32 Conclusions-I  We believe we can get to effective volumes large enough to detect a large sample of GZK neutrinos at the South Pole using radio and/or acoustic techniques ● If IceCube or ANITA see some events, IRA will see ~100 with several years’ operation—start to do astronomy with them ● Also, start to do particle physics—measure neutrino-nucleon cross section at ~100 TeV CM to 30% (Ref.: Connolly, ARENA 2005)  The cost of drilling (shallower and narrower) holes and of the individual radio and acoustic elements is very reasonable (very roughly, ~$30k/hole for drilling, ~$50k for radio + acoustic sensors)  Operating optical, radio and/or acoustic detectors in coincidence will not only produce more convincing individual events, but also extend the reach and accuracy compared to any one detector alone

33. IRA April 2006 D.F. Cowen/IceCube Collab. Beyond IceCube Beijing UHE  Workshop 33 Conclusions-II IceCube will be a vast improvement over AMANDA, but some things never change… IceCube