1. Steps towards a cosmogenic neutrino detector at the South Pole Summary of meeting on Sep 14 Opportunities - outer ring extension Acoustic & Radio technique, parameter space Science case Strategy discussions Albrecht Karle

2. Utrecht Sep 14, R&D pre-meeting on GZK neutrino detection at the Pole: Attendance: ~25 people from the –acoustic group and –radio group Including and notworthy Leif Gustavsson - Uppsala Amy Connolly, Ryan Nichols - UC London First time we had such a meeting organized from within the collaboration including groups outside IceCube

3. Larger geometries: Higher cross over Greater gain at high energies High Energy IceCube Optimization study Investigated options for optimized positioning of last 9 strings Motivation: Improve high energy response. Significant impact on drilling. RESULT: Gain in effective area 10% to 30% (50% at GZK energies ) (depending on configuration) IceTop coincidence event rate increases

4. Gains for the tested configurations (remember they include constant angular resolution cuts) 10 degree AR Geometries: original, NDL, 1.5x, 2.0x, 2.5x, 0.8 km, 0.9 km, 1.0 km Event rate ratio to the original geometry 1.5x2.0x2.5x 0.8km0.9km1.0km original 1.0 km NDL 10 degree AR Geometries: original, NDL, 1.5x, 2.0x, 2.5x, 0.8 km, 0.9 km, 1.0 km Event rate ratio to the original geometry original 1.0 km Some performance loss at lower energies is recovered with deep core IceCube extenstion [2] Performance reaches the average cross sectional area fractional increase at higher energies

5. 80 total strings including 12 in the outer ring (1 km radius) 6 outer ring strings + 1 in center with optical + radio + acoustic Simulated array geometry: HORUS normal optical string with 60 DOMs 1 every 17 m from 1.45 km to 2.45 km 60 acoustic sensors 1 every 15 m from 215 to 1100 m 5 radio antennas 1 every 100 m from 200 to 600 m Hybrid Optical Radio Ultrasound Setup

6. Diffuse E -2 µ -spectrum peaks at 1 PeV - original and driving motivation Neutrino event energy spectrum after energy cut for a 3 year diffuse analysis. Signal events peak at ~1PeV Optimize final detector configuration for higher energy range, to maximize sensitivity of IceCube.

7. EHE - Experimental limits IceCube 80, 1yr arXiv:0711.302, apj arXiv:0705.1315, prd Figure from

8. Summary of review based on Auger results by T. Stanev and D. Seckel at APS Revisit GZK  in light of AUGER AUGER: –Spectrum, AGN, Mixed composition, E Calibration Reasonable choices: –AGN luminosity evolution w/  = 1.4 –E c = 10 21.5 –Mixed composition –HIRES normalization (AUGER * 1.25) Results ~ 2-3 below ESS.

9. Neutrino induced cascades produce 3 types signals: optical, acoustical and radio signals air interaction  particle shower ~10 12 particles interaction  particle shower ~10 12 particles (1)Optical Cherenkov pulse: ~500 m (works below 1400m because of ice and cosmic rays) (2) Askaryan radio cone ~1 km (100MHz - 1GHz) (3) Askaryan acoustic pancake: ~km? Total internal reflection at surface (firn layer)? Depending on angle. ice radio and acoustic waves travel farther than light in ice They require less drilling as they can travel through bubbly ice and firn (radio) Energy scale in this cartoon: o(1 EeV)

10. Ray tracing reminder Radio waves Sound waves HL JV

11. R&D Future extension ideas: UHE Radio Augmentation - here IceRay version AURA-18 - and possibly acoustic instrumentation ICERAY GZK neutrinos (10 17-19.5 eV), at lowest possible cost: o(10)/3yr –Version shown may be too small Chance of hybrid events with IceCube –Primary vertex calorimetry in radio, HE muon or tau secondary in IceCube

12. Detector comparison of GZK rates per year Cosmogenic neutrino Model 3m, N=60 events yr -1 50m, N=36 events yr -1 50m, N=60 events yr -1 100m, N=36 events yr -1 200m, N=18 events yr -1 Iron-only UHECR0.30.50.71.00.6 Engel, Seckel, Stanev 2001, base model1.52.43.14.22.9 ESS model (stronger)  m=0.3,  =0.7 2.43.84.96.74.6 Waxman-Bahcall-based GZK flux model2.74.25.517.65.0 Protheroe/other Std-model GZK fluxes3-4.74.7-7.86.2-9.68.5-12.55.6-10 Models with strong source evolution7.6-1312-2115-2520-3514-36 Maximal GZK fluxes, saturate all bounds14-2724-4029-5540-8032-47 Detector probable cost evaluationexcellentVery goodgoodOK Detector performance evaluation:OKgoodVery goodexcellentgood Disfavored by data Standard Models too Strong? Select 50 m depth, N=36 array as preliminary IceRay baseline Best cost-performance (weighted more by cost) Uses proven firn-drill technology 3 events/yr (divide by 2 to 3)

13. Bigger picture - Staged IceCube Enhancements How to get from here to there? D. Besson et al. astro-ph/0512604 Optical: 80 IceCube + 13 IceCube-Plus (astro- ph/0310152) - unlikely at this point Radio / Acoustic: ~ 10 events/yr (divide by 2 - 3)

14. Large detector: effective volumes & event rates I: IceCube O: Optical R: Radio A: Acoustic ESS GZK flux model (   = 0.7) [R. Engel, D. Seckel and T. Stanev Phys. Rev. D 64, 093010 (2001)] Detection option GZK events/year *) IceCube0.7 Optical1.2 Radio12.3 Acoustic16.0 Optical+Radio0.2 Optical+Acoustic0.3 Radio+Acoustic 8.0 !!! Opt.+Rad.+Acou.0.1 TOTAL21.1 5 antennas/string to 600m 300 hydrophones/string to 1200m (assumed cost equivalent in study)

15. Parameters for evaluation ConfigurationOptions Detection principleRadioAcousticOptical Granularity in x-y and in z HighLowclusters Complexity of sensor and recorded information Precise waveform capture Simplistic: eg. T, ToT, or log(amp) Polarization (radio) DrillingDiameterDepth (50, 200, 1200 m) Hot water or mechanical Communication/powerWired/wirelessbandwidth

16. Drilling Parameters: Depth, diameter, Dry or hot water Operation: Crew size, power, time per hole, cost Findings from 2 drilling workshops held at UW in 2008, Organized by PSL

17. Added for evaluation –Caltech drill: 2 km, 25 cm, 9 crew, hot water, 1200m, ~1000 gal fuel, several days.

18. Constraints Minimal number of events Reliable detection and background rejection: –Event information, enough hits and/or information on pulseshape and polarization Power draw from station (eg < 10 kW) Construction impact: drilling, deployment, personnel Total construction time Cost

19. Discussion on hybrid, IceCube & radio & acoustic Reason: absence of natural calibration signals (such as atm. neutrinos). Hybrid is a powerful way to demonstrate that background is understood and to calibrate. Optical: can get lucky, but can’t make it a planning assumption to see events / coincidences. Simultaneous detection of radio and acoustic would be beautiful evidence of an event Challenge: Acoustic detection (even in optimistic assumptions otherwise) requires deep drilling -> quantum jump in drilling costs and time, that may be deciding factor. Question to answer is, –whether it is cost efficient to pursue redundancy and BG rejection this way? –Or if sufficient redundancy can be achieved radio only.

20. Amy Connolly, UCL

21. Work towards Simulating specific models And understanding detector response RICE limit

22. Amy Connolly, UCL

23. Three-prong hybrid air shower studies (1) IceTop, (2) Muons in deep ice, (3) Radio Proposal submitted for R&D to European funding agencies Options for IceTop Radio Extension Expansion of surface array   Veto for UHE neutrino detection InIce Infill surface array   Hybrid CR compositon

24. EMI test bed -EMI monitoring ~2km out of the station. -Ground screen above array to block galactic, solar, aircraft and surface RF noise - 115-1200 MHz - Hardware exist -Independent proposal submitted -Also: checking option to use firn holes near and away station to study firn and EMI emission (not a part of IceRay).

25. Phases 1)Explorations of techniques, sensor development, experience, measurements of ice properties R&D on acoustic and radio SPATS, RICE, AURA, NARC, other activities Ongoing, conclusions in 2009 and 2010 2) IceRay scale detector  Large enough to measure o(10) events in 3 years in reasonably conservative assumption on flux and detector efficiency  Proposal 2010 3) Larger scale cosmogenic neutrino detector o(100) events, beyond 2015

26. Possible near term timeline:2008-2009-2010 - Working group and collaboration building - Write „Letter of Intent“ and sign in spring 2009 to demonstrate Commitment of groups science case expected improvement to previous experiments time scenario and milestones - Finish basic exploration of ice properties - Start extensive MC studies of different detector options - Start sensor and electronic prototyping - Track down number of different detector options based on above results - Proposal 2010