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

P. Gorham, Granlibakken 2007 Science roots: the 60’s… : 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! – : Askaryan’s hypothesis remained unconfirmed – : Argonne & SLAC beamtests confirm strong radio Cherenkov from showers in silica sand – , salt & ice also tested, all confirmed Saltzberg, et al PRL 2001 Goprham, et al PRD 2004

P. Gorham, Granlibakken of 21 Measurements for Cosmic rays  predict Neutrinos Neither origin nor acceleration mechanism known for cosmic rays above eV, after 40 years! A paradox: No nearby sources observed distant sources excluded due to collisions with microwave bkg Neutrinos at 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

P. Gorham, Granlibakken 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 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

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

P. Gorham, Granlibakken 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

P. Gorham, Granlibakken 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

P. Gorham, Granlibakken of 21 ANITA-lite Prototype flight 2004 Piggyback Mission of Opportunity on the 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 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

P. Gorham, Granlibakken 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

P. Gorham, Granlibakken 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)

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

P. Gorham, Granlibakken 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)

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

P. Gorham, Granlibakken 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

P. Gorham, Granlibakken 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

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

P. Gorham, Granlibakken 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

P. Gorham, Granlibakken of % of triggers: incoherent thermal noise

P. Gorham, Granlibakken 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)

P. Gorham, Granlibakken 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