RICE experience/ANITA implications

1. RICE experience/ANITA implications • Review of RICE progress, to date • Current Status • Focus on major systematic errors and status of understanding of background • Possible future improvements and prospectus

2. Scorecard (in hindsight) • (-) electron testbeam run (kudos to David & Peter) • (-) proton testbeam run (FNAL plans) • (-) more ice properties studies (limited time at Pole), despite limited and conflicting measurements of dielectric constants of cold ice (alfa0.ps & seckelfig) • (-) invested considerable personpower in ZHS/GEANT shoot-out • EZ pointed out that one of the default GEANT settings not tuned for tracklength studies • still not fully resolved - GEANT 3.21/4 gives 10% less tracklength, but 10% more peak E-field @ 1GHz • more high-frequency power

3. Scorecard, cont. • (-) Development of Matched Filter lagged • (-) Single channel gain calibration needs more fine-tuning and work with Tx<->Rx data • (-) Identified: • MAPO backgrounds • AST/RO backgrounds • Background X (correlation with solar flare activity???)

4. Scorecard (in hindsight) • (+) demonstrated viability of radio technique in ice; no show stoppers en route to publication • (+) Kept costs down by: • 2 undergrads == 1 postdoc (by necessity) • using duct tape • using more duct tape • using more more duct tape • using local grocery store as lab space

5. Duct tape. Duct tape. Duct tape

6. Antenna testing in the Checkers supermarket vegetable freezer, prior to deployment

7. Limitations & systematics (I) • Timing resolution (particularly for distant vertices, where most of neutrino interactions occur) (MC) • calibrate ch.-response online? (like in-line guitartuner) • matched filter to get to large Aeff and <ns time resolution. • Ice properties - Re(epsilon) and Im(epsilon), particularly through the firn • Plan to do high-statistics Tx measurement 2002-03? • And through lower depths (Greenland data?) • (to what extent does surface act like giant RF mirror?) • Inability to exploit high-frequency power (MC) • Non-optimized antenna spacing, antenna BW (MC)

8. Limitations & Systematics (cont.) • Modeling uncertainties: • Raw signal power, G4 vs. G3.21 (ABAN=0) vs. ZHS • 30% discrepancy between G3.21 (ABAN=1) and ZHS now <10%. • BUT: power spectra (E(f)) disagree • E(peak)/tracklength ratio disagree at 10-15% level • LPM effect, coherence between hadronic & EM pieces • Basic Problem: Veff grows with r, so most of Veff is at very edge of sensitive volume!!!

9. Systematics - details, in sequence • Timing resolution • Compare 4 different hit-times: • LeCroy 3377 TDC time (500 ps) • Time of maximum voltage in a waveform (integrated over 1 ns) • Time of 1st 6-sigma excursion in a waveform (1 ns) • Time as returned by a matched-filter (Figs. Showing different possible signals, depending on antenna response). • Lower thresholds, better than 1 ns timing resolution • LOW THRESHOLDS == MORE EFFECTIVE AREA! • IDEALLY - want matched filter in hardware, for now, only software • Figure-of-merit: vertex resolution using low-amplitude transmitter evts., comparing all four hit times:

10. The test signals Have k ranging +/- 20%, and Frequency ranging +/- 10%. Test Signals The “junk” signalsinclude spikes, decaying oscillations with wrong frequency, correct frequency with no decay, and large patches of white noise. Junk Signals Signals + Noise Signal Squared Start of each signal is 200 time steps after previous signal. Amplitude Energy Signal to Noise in this run: 5:1

11. A2/C2 The quality measure spikes sharply for the test signals. Although it looks small even the spike at 600 is substantial. If we drop the spectrum match from the measure, we pick up decaying osillators of any frequency, and a few other bumps that could be false positives.

12. Signal to noise = 3:1

13. Signal to Noise: 0:1 Distribution of Q for K and/or w deviating from expected value Ksignal 0.6 K 0.8 K K 1.2 K 1.4 K 1.2 w w 1.1 w 0.8 w 0.9 w wsignal

14. Signal to Noise: 2:1 Distribution of Q for K and/or w deviating from expected value 0.6 K 0.8 K K 1.2 K 1.4 K 1.2 w w 1.1 w 0.8 w 0.9 w

15. Signal to Noise: 5:1 Distribution of Q for K and/or w deviating from expected value 0.6 K 0.8 K K 1.2 K 1.4 K 1.2 w w 1.1 w 0.8 w 0.9 w

16. Signal modeling and transmission • LPM & Re(epsilon) - attenuation length dictates Veff (or Aeff) at high energies • Im(epsilon) - ray tracing through the firn with ANITA will be more difficult than with RICE (hopefully, RICE 2002-03 data will help here). • Antenna properties better with ANITA - calibrated in air (RICE calibrated initially in air, then cross-checked in ice).

17. Measurements of field atten. length Primary dependence on temperature profile through the ice Also: extra- polate into <GHz regime using high-frequency lab data + Debye model (matsuoko)

18. Temperature v. depth measurements

19. Propagation – Im(dielectric constant) • Index of refraction • Absorption Simultaneous fit to Rx, Tx positions and n(z)

20. New simulation results (ABAN=0) Can we measure high-frequency power?

21. Effective height measured at KUATR Measurements made in air, then “evolved” to n=1.78

22. Pulse shape simulation Problem: How to apply matched filter in hardware? Need 1 GHz BW Tx calibration signal Background taken from data sample Disc. threshold

23. Compare MC vs. data for shape Need: transmitter with calibrated and well-defined shape to test complex transfer function

24. Single Channel Calibrations • TX….RX • antenna + amplifier calibrations • cable (TX, RX) and filter • relative geometry of TX/RX 200-500 MHz: +/- 3 dB (E) ANITA will need full circuit gain over long baseline, as well. Best if Tx==Rx

25. What the previous slide means • We superimpose CW on thermal floor, and find that the thermal floor is consistent (within 1 dB) of Tnoise+Tamplifier noise figure for f~200-800 MHz • RF x-talk between RICE Rx and AM-cable either somehow averages out or can be neglected • RF x-talk from RICE Rx to RICE Rx not seen (verified using pulser tests also), although dt>100 ns between successive channels. X-ringing in ANITA? • Ice absorption negligible on the scale of the RICE array (~200m) for f~200-800 MHz.

26. Background characterization • There is a strong, short-duration source which has persisted over the 4 years that we have taken data • “Diffuse” vertex location, rejectable as z>-50 m source with 98-99% efficiency on-line. • Seeking better bkgnd. Rejection for >2002 • Variable numbers of hit channels, large amplitudes, double pulses often evident (not a raytracing effect) • Strongest in “dry holes” (also highest gain holes) • Weakest in summer, strongest in winter. • Consistent with anthropogenic source • Also consistent with solar flare source??? Circumstantial evidence. Investigating now. Have looked (sans success) for shadowing - but RF bkgnd. probably doesn’t track visible.

28. Field-of-view dependence on n • Because of refractive effects, viewing volume of in-air antennas is VERY sensitive to knowledge of index-of-refraction (Fig.)

29. Can ANITA see RICE Tx? • For 300 V p-p Tx coupled to TEM horn, Z~50 Ohm, r~106 m, E~1 mV/m (~10 Vthermal) • CW may be better, using spectral analysis • Other alternatives - broadcast from SIPLE / Dome C / McMurdo / Vostok / AGO’s...

30. LPM effect and uncertainties • UHE e- no longer see “distinct” nuclear scatterers in medium=>brem quasi-continuous. • Perform coherent sum of scattering amplitudes over “coherence length”. • Feynman diagrams cancel pairwise • Brem xsct reduced, shower is “elongated” • Established effect (measured by Stu Klein), however, untested (obviously) at >PeV energies • Uncertainties remain (e.g., above 200 PeV, photonuclear interactions competitive with brem? If so: a) photoproduction of hadrons in shower, b) higher interaction xsct=>elongation reduced.

31. LPM and hadronic showers 2. 1. 3 m k 0. f f e 1. - V g o L 2. - 3. - 1. 2. 3. 4. 5. 6. Log E PeV s “Hadronic” Es = 20% En Without LPM With LPM

32. Future Plans • 3-year proposal submitted to NSF for 800K June 1. • At usual rate of RICE funding, expect 50K-80K • Focus on improving DAQ (pg/sk high BW ANITA digitizer, will require at least one dedicated gradstud) • ICECUBE digitizers probably too low in BW • Hope for co-deployment with ICECUBE using ANITA digitizers + updated trigger formation hardware/software. • DS: X-RICE

33. Systematics (see astro-ph/0206371)

34. RICE, review and current status • 1995-99: development and deployment • 1996: main funding (230K MRI) • 1999: 130K supplement • Since total budget averages ~50K/yr: • have relied heavily on undergrad/grad students rather than hiring postdocs (3 Goldwaters!) • design compromises: coax signal transmission, off-the-shelf electronics (digital scopes + CAMAC) • NO experimental results without the help of AMANDA!! • 1999-2002: calibration, analysis, simulation, publication • 2002: first papers appear (2) in Astropart. Phys.