1. 1 Radio detection of high energy particles in dense media, & ANITA Peter Gorham University of Hawaii Manoa Department of Physics & Astronomy Co-Is: S. Barwick, UCI; J. Beatty, OSU, W. Binns, M. Israel, Wash. U. St. Louis, M. DuVernois, U. Minn., K. Liewer & C. Naudet, JPL/NASA; D. Saltzberg, UCLA, G. Varner, UH Manoa

2. P. Gorham, Granlibakken 2007 Science roots: the 60’s…++ 1962: G. Askaryan predicts coherent radio Cherenkov from particle showers in solid dielectrics – His applications? Ultra-high energy cosmic rays & neutrinos – Mid-60’s: Jelley & collaborators see radio impulses from high energy cosmic ray air showers – -- from geo-sychrotron emission, not radio Cherenkov, false alarm! – 1970-2000: Askaryan’s hypothesis remained unconfirmed – 2000-2001: Argonne & SLAC beamtests confirm strong radio Cherenkov from showers in silica sand – 2004-2006, salt & ice also tested, all confirmed Saltzberg, et al PRL 2001 Goprham, et al PRD 2004

3. P. Gorham, Granlibakken 2007 3 of 21 Measurements for Cosmic rays  predict Neutrinos Neither origin nor acceleration mechanism known for cosmic rays above 10 19 eV, after 40 years! A paradox: No nearby sources observed distant sources excluded due to collisions with microwave bkg Neutrinos at 10 17-19 eV required by standard-model physics Lack of neutrinos:  UHECRs not hadrons?!  Lorentz invariance wrong?!  New physics? galactic Extra- galactic “GZK cutoff ” process p,  +   pions, e+e- GZK neutrinos

4. P. Gorham, Granlibakken 2007 4 of 21 Neutrinos: The only long-range messengers at ultra-high energies Photons lost above 30 TeV: pair production on IR & 3K  wave background Charged particles: scattered by B-fields or 3K bkg photons at all energies But we know there are sources up to at least 10 20 eV Ergo: Study of the highest energy processes and particles throughout the universe requires ultra-high energy neutrino detectors Region not observable In photons or Charged particles

5. P. Gorham, Granlibakken 2007 5 of 21 How to detect UHE neutrinos? Ice RF clarity: 1.2 km(!) attenuation length Effective “telescope” aperture: ~250 km 3 sr @ 10 18.5 eV ~10 4 @ km 3 sr 10 19 eV (Area of Antarctica ~ area of Moon) ~4km deep ice! Typical balloon field of regard

6. P. Gorham, Granlibakken 2007 6 of 21 ANITA Gondola & Payload Antenna array Overall height ~8m Solar panels Antarctic Impulsive Transient Antenna--ANITA NASA start in 2003, first LDB launch in ‘06-07, 10 day baseline mission Ultra-broadband antenna array, views large portion of ice sheet looking for Askaryan impulses Instantaneous balloon field of view ~320ps Measured impulse response Quad-ridged-horn dual-pol antenna (lower panels removed here) DAQ & flight computer

7. P. Gorham, Granlibakken 2007 7 of 21 ANITA as a neutrino telescope ANITA sees a band of sky just below the “visible” horizon The band is different for different longitudes of the balloon Pulse-phase interferometer (150ps timing) gives intrinsic resolution of <0.5 o elevation by ~1 o azimuth for arrival direction of radio pulse Neutrino direction constrained to ~<2 o in elevation by earth absorption, and by ~3-5 o in azimuth by polarization angle

8. P. Gorham, Granlibakken 2007 8 of 21 ANITA-lite Prototype flight 2004 Piggyback Mission of Opportunity on the 03- 04 TIGER* flight, completed mid-January 04 ANITA prototypes & off-the-shelf hardware used 2 dual-pol. ANITA antennas w/ low-noise amps 4 channels at 1 GHz RF bandwidth, 2 GHz sampling 18.4 days flight time, set the best current limits on UHE neutrino fluxes Paved the way for a full-scale ANITA payload *Trans-Iron Galactic Element Recorder

9. P. Gorham, Granlibakken 2007 9 of 21 June 2006, SLAC T486: “Little Antarctica” Stanford Linear accelerator Particle (e - ) bunches with composite energy same as UHE neutrinos Best possible calibration for ANITA

10. P. Gorham, Granlibakken 2007 10 of 21 ANITA & Askaryan effect in ice Impulses are band-limited, highly polarized, as expected Very strong--need 20dB ‘pads’ on inputs--signals are +95dB compared to Antarctic neutrino signals, since we are much closer 10 ns

11. P. Gorham, Granlibakken 2007 11 of 21 Nov. 2006, Antarctica: Putting it together The Long Duration Balloon Base at Williams field ~7 miles out on Ross Ice shelf, smooth, flat ice, 80m deep a first-class field operation, run by NASA’s Columbia Scientific Balloon Facility (Palestine Texas)

12. P. Gorham, Granlibakken 2007 12 of 21 ANITA “hangtest,” Sunday 12/3/06 Final pre-flight checkout Payload is ready for launch

13. P. Gorham, Granlibakken 2007 13 of 21 Launch: December 15, 2007 ANITA at float (123Kft) See through amateur telescope from the South Pole Size of the Rose Bowl! (thanks to James Roth)

14. P. Gorham, Granlibakken 2007 14 of 21 Landing…~360 miles from S.Pole Ouch! What a drag… But instrument & data OK

15. P. Gorham, Granlibakken 2007 15 of 21 ANITA flight path 35 days, 3.5 orbits Anomalous Polar Vortex conditions Stayed much further “west” than average In view of stations (Pole & MCM) ~30% of time

16. P. Gorham, Granlibakken 2007 16 of 21 Flight sensitivity snapshot (preliminary) ANITA sensitivity floor defined by thermal (kT) noise from ice + sky Thermal noise floor seen throughout most of flight—but punctuated by station & satellite noise Significant fraction (>40%) of time with pristine conditions  T~ 50K (Sun+Gal. Center) ~ 200K T anti-correlated to altitude: higher altitude at higher sun angle sun+GC higher  farther off main antenna beam

17. P. Gorham, Granlibakken 2007 17 of 21 Validation data: borehole pulser RF Impulses from borehole antenna at Williams field Detected at payload out to 300-400 km, consistent with expected sensitivity Will allow trigger & pointing calibration

18. P. Gorham, Granlibakken 2007 18 of 21 Trigger pattern, borehole pulser Trigger pattern requires >3 antennas (9 of 24 signal channels) in both upper and lower 16-antenna rings Negligible accidentals, but ~4-5Hz from thermal noise But Thermal noise is incoherent in spatial & temporal character

19. P. Gorham, Granlibakken 2007 19 of 21 99.99+% of triggers: incoherent thermal noise

20. P. Gorham, Granlibakken 2007 20 of 21 ANITA’s potential science impact ANITA-lite: 18.4 days of data, net 40% livetime with 60% analysis efficiency for detection Z-burst UHECR model ( annihilation -->hadrons) excluded:  expect 6-50 events, see none Highest Toplogical defect models also excluded ANITA projected sensitivity (3 flights):  e    included, full-mixing assumed  45 days exposure at 67% efficiency assumed  We are roughly within a factor of 2 with 1 st flight Strongest limits: all radio ’06-07 flight (preliminary)

21. P. Gorham, Granlibakken 2007 21 of 21 Summary & Plans ANITA may have first glimpse of the ultra-high energy neutrino universe already on disk Data disks returned from Antarctica a couple of weeks ago Two independent blind analyses just getting started Preliminary results by late summer? ANITA II proposed to fly in 2008