Radio detection of high energy particles in dense media, & ANITA

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. 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 P. Gorham, Granlibakken 2007 Goprham, et al PRD 2004

3. p, g + g(3K) pions, e+e- • GZK neutrinos “GZK cutoff ” process Measurements for Cosmic rays  predict Neutrinos • Neither origin nor acceleration mechanism known for cosmic rays above 1019 eV, after 40 years! • A paradox: • No nearby sources observed • distant sources excluded due to collisions with microwave bkg • Neutrinos at 1017-19 eV required by standard-model physics • Lack of neutrinos: • UHECRs not hadrons?! • Lorentz invariance wrong?! • New physics? galactic Extra- galactic P. Gorham, Granlibakken 2007

4. Neutrinos: The only long-range messengers at ultra-high energies Region not observable In photons or Charged particles • Photons lost above 30 TeV:pair production on IR & 3K mwave background • Charged particles:scattered by B-fields or 3K bkg photons at all energies • But we know there are sources up to at least1020 eV • Ergo: Study of the highest energy processes and particles throughout the universe requires ultra-high energy neutrino detectors P. Gorham, Granlibakken 2007

5. How to detect UHE neutrinos? Typical balloon field of regard ~4km deep ice! Ice RF clarity: 1.2 km(!) attenuation length • Effective “telescope” aperture: • ~250 km3 sr @ 1018.5 eV • ~104 @ km3 sr 1019 eV • (Area of Antarctica ~ area of Moon) P. Gorham, Granlibakken 2007

6. Antarctic Impulsive Transient Antenna--ANITA ANITA Gondola & Payload • 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 DAQ & flight computer Solar panels Antenna array Instantaneous balloon field of view (lower panels removed here) Overall height ~8m ~320ps Measured impulse response Quad-ridged-horn dual-pol antenna P. Gorham, Granlibakken 2007

7. 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 <0.5o elevation by ~1o azimuth for arrival direction of radio pulse • Neutrino direction constrained to ~<2o in elevation by earth absorption, and by ~3-5o in azimuth by polarization angle P. Gorham, Granlibakken 2007

8. 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 P. Gorham, Granlibakken 2007

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

10. 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 P. Gorham, Granlibakken 2007

11. 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) P. Gorham, Granlibakken 2007

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

13. 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) P. Gorham, Granlibakken 2007

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

15. 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 P. Gorham, Granlibakken 2007

16. Flight sensitivity snapshot (preliminary) <Tant>~ 200K • 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 DT~ 50K (Sun+Gal. Center) • T anti-correlated to altitude: • higher altitude at higher sun angle • sun+GC higher  farther off main antenna beam P. Gorham, Granlibakken 2007

17. 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 P. Gorham, Granlibakken 2007

18. 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 P. Gorham, Granlibakken 2007

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

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

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 P. Gorham, Granlibakken 2007