Spencer Klein, LBNL & UC Berkeley n GZK Neutrinos n Radiodetection The moon as a cosmic target n ANITA – floating over Antarctica n Future experiments in Antarctic ice n Conclusions

p  e+e-e+e- ++ ++ ++  (3 0 K) 2 , 1 e 1  :1 e,: 1  Oscillations Probing the EHE Cosmos At energies above 4  eV energies, only have a cosmic (> 100 Mpc) range. u Other particles interact with the 3K cosmic microwave background radiation   pair produce & heavier nuclei photodissociate Protons are excited to  + u Greisen-Zatsepin-Kuzmin (GZK) interactions from in-flight p   + excitation are ‘GZK neutrinos’  “Guaranteed’ signal’ n Protons & nuclei bend in interstellar magnetic fields Accelerator (AGN?)

GZK Neutrinos n Flux depends on cosmic-ray spectrum & composition energy spectrum probes cosmic evolution out to redshift ~ 3-5 u As redshift increases, the cosmic microwave photons are more energetic F Protons interact at lower energies. spectrum peaks just below eV ( e,  ) with a 2 nd peak at eV ( e ) u All experiments focus on higher energy peak  from ,K decay have e :  :   1:2:0 u Oscillations alter this to a nearly 1:1:1 ratio Engel, Stanev, Seckel, PRD 64, (2001) ,K decay Neutron  decay

Neutrino Interactions Cross-section is large enough so that are absorbed in earth  are either horizontal or down-going  Measure  N from zenith angle distribution F Sensitive to low-x parton distributions & some new physics n Radio signals come from EM and hadronic showers n 20% of neutrino energy goes into a hadronic shower 80% of e energy produces an electromagnetic shower u EM showers are elongated by LPM effect, altering radio emission  Many higher energy (>10 20 eV) experiments ignore e showers For E > eV, e &  interact hadronically, limiting growth in shower length L. Gerhardt & SK, 2010 LPM Hadronic Bethe-Heitler Full Log 10 Shower Length (m) Log 10 E (eV)

Radio Emission from Showers n Showers contain ~ 20% more e - than e + u Compton scattering of atomic e - in target u Positron annihilation on atomic e - n For wavelengths > transverse size of the shower, the net charge emits Cherenkov radiation coherently.  Radio energy ~ E 2 u Maximum frequency ~ few GHz F Medium dependent u Radiation at Cherenkov angle F Angular distribution broadens at lower frequencies. n Studies with 25 GeV e - beams at SLAC incident on salt, sand and ice targets u Confirmed theoretical calculations SLAC data:D. Saltzberg et al., PRL 86, 2802 (2001) Angles: O. Scholten et al. J.Phys.Conf.Ser. 81, (2007) Emission Angle 2.2 GHz 100 MHz SLAC data Shower Energy (eV) E field 1 m) Shower Energy (eV) Relative Intensity Frequency (MHz)

Zooming in on Neutrinos n Radio waves from the moon u 240,000 km range increases threshold to >>10 20 eV F Above most of GZK energy spectrum n FORTE satellite: radio pulses from Greenland n ANITA Balloon Experiment circled Antarctica  Looking down, for interactions in ice F Up to 650 km from detector u Closer than the moon; threshold eV F Upper portion of GZK peak n Antennas Embedded in Antarctic ice u Pioneered by RICE experiment u Detectors can reach eV threshold, F Most of the GZK spectrum u ARA and ARIANNA experiments at prototype stage

Lunar Signals n Sensitive volume depends on frequency u Radio absorption length ~ 9 m/f(GHz) sets maximum sensitive depth u High frequency searches see radio waves near the Cherenkov cone - near edge (limb) of moon u Lower frequency searches see a broader angular range F Larger active volume n But… there is more radio energy at high frequencies n Backgrounds from cosmic-ray moon showers T. R. Jaeger et al., arXiv:

Lower frequency Experiments n Westerbork 64 m dish u MHz u No events in 47 hours of observation n Low frequency array for radio astronomy (LOFAR) u 36 stations in Northwest Europe F MHz 48 antennas/station F MHz 96 antennas/station n Square Kilometer Array u Proposed radio telescope array with 1 km 2 collecting area F In South Africa or Australia O. Scholten et al., PRL 103, (2009).

Higher Frequency Experiments n Australia Telescope Compact Array u 6 nights of data with 6 22 m dishes F Beam size matches the moon u 600 MHz bandwidth ( GHz) F De-dispersion filter needed n Resun u 45 hours of data with 4 25-m VLA (very large array) dishes u 1.45 GHz u 50 MHz bandwidth u Resun-B is planned Lunaska - C. W. James et al., PRD 81, (2010) Resun – T. R. Jaeger et al., arXiv:

Lunar results n Thresholds >> eV u Small fraction of GZK spectrum u Probes exotic models, like topological defects n Multi-dish apparatus reach lower thresholds n Lower frequency experiments (NuMoon) have higher thresholds, but a larger effective volume, giving them lower limits n Lunaska (ATCA) presented two limits for different models of lunar surface roughness Log 10 E (GeV) E 2  (E) (GeV cm -2 s -1 sr -1 ) Log 10 E (GeV) E 2  (E) (EeV km -2 s -1 sr -1 ) GZK

ANITA Balloon n Two flights u 35 day flight in 2006/7 u 31 day flight in 2008 u Altitude ~ 35 km n 40 (32) horn antenna search for radio pulses out to the horizon ( ~ 650 km) u Separate channels for vertical and horizontal polarization u 26.7 M trigger on broadband pulses F Mostly thermal noise n Calibrations from buried transmitters buried measure signal propagation through ice, firn and snow-air interface.

ANITA Results n Cuts remove thermal, payload & anthropogenic noise, and misreconstructions n 5 events remain u 3 horizontally polarized events are likely reflected signals from cosmic- ray air showers n 2 vertically polarized events are consistent with signal u Expected background 1  0.4 n Upper limit constrains ‘interesting’ GZK models n ANITA-3 flight requested w/ more antennas and better trigger Waveform from a candidate event Time (ns) Log 10 E (GeV) E  (E) (km -2 yr -1 ster -1 ) Posters by Abigail Vieregg and Eric Grashorn

Antarctic In-Ice Detectors n Sensitive to most of GZK spectrum u Key to probe cosmic evolution u Thresholds ~ eV n Planned Target Volume 100 km 3  100 GZK in 3-5 years  Measure  N n Two funded proposals funded for prototype installations u Sensitivity scales with $$$ F -- > No plots showing effective area… u ARA at the South Pole u ARIANNA on the Ross Ice Shelf n Logistics in Antarctica can be tough u Winter power… Cos(  z ) # Events Plot by Amy Connolly

Askaryan Radio Array (ARA) n Radio antenna clusters in 200 m deep holes at the South Pole u Clusters on km triangular grid n Series of prototypes deployed in IceCube holes n Attenuation length > 500 m u Measurement sensitive to reflection coefficient of ice-rock interface n Electronics under discussion u Possible variation: more, but simpler channels, with time-over- threshold electronics n Hole drilling and power options being studied Poster by Kara Hoffman

ARA stations and antenna clusters 4 receiver strings + 1 buried calibration transmitter/cluster Prototype Development in progress Multiple antennas for up/down discrimination

ARIANNA concept n In Moore’s Bay on the Ross Ice Shelf u ~ 570 m of ice floating on seawater F The smooth ice-water interface reflects radio waves like a mirror u 110 km from McMurdo station n Sensitive to downward-going neutrinos u Larger solid angle n Reflection increases collection area n Stations with 4-8 dipole antennas in shallow trenches u 4-8 m antenna separation gives directional info u Orientations measure pulse polarization Dotted lines show reflected signal Signal reflection from interface Ice Water S. Barwick, NIM A602, 279 (2009).

ARIANNA in the Field n Site characteristics studied in 2007 & 2009 u Ice thickness 572  6 m u Radio attenuation length ~ 500 m F Ice-water interface attenuation < 3 db n Prototype deployed in Dec u 4 Log-periodic dipole antennas F ~ 50 MHz to 1 GHz F 2 GS/s waveform digitizer readouts u Triggered on >=2/4 antennas F After temporary internet connection was removed, triggers were thermal noise u Solar and wind power generators F It worked well until the sun set u Iridium Modem n Design of a 7-station array is mostly funded and in progress L. Gerhardt et al., arXiv: ; D. Saltzburg et al., submitted to Astropart. Phys.

ARA and ARIANNA FactorARAARIANNA Radio Atten.Length m ? m AcceptanceHorizontalHorizontal + Downgoing LogisticsDrilling, South Pole m elevation Green Field Site

Conclusions n Neutrino interactions at energies above eV produce substantial coherent radio Cherenkov emission. u The radio energy increases as the square of the neutrino energy. u These signals have been studied in beam tests at SLAC. n Many experiments have searched for radio emission from cosmic neutrino interactions. u Radio-telescope arrays have searched for signals of n interactions in the moon, with a threshold E > eV. u The ANITA balloon experiment has set limits that constrain current predictions on the GZK neutrino flux. u The proposed ARIANNA and ARA radio detectors will emplace radio antennas on the Ross Ice Shelf and at the South Pole respectively.  Sensitive to the entire GZK energy range Can probe cosmic evolution of high-energy sources.  They will also measure  N at EHE energies

UHE Neutrino Posters n Recent Results and Future Prospects of the South Pole Acoustic Test Setup u Rolf Nahnhauer n UHE neutrino detection with the surface detector of the Pierre Auger Observatory u Jose Luis Navarro n New Results from the ANITA Search for Ultra-High Energy Neutrinos u Abigail Vieregg n ANITA and the Highest Energy Cosmic Rays u Eric Grashorn n The Askaryan Radio Array u Kara Hoffman n The GEM-EUSO Mission to Explore the Extreme Universe u Gustavo Medina Tanco n A small Air Shower Particle Detector Array dedicated to UHE neutrinos u Didier Lebrun

Backup Slides

Shower SLAC n Pulses of GeV e- were directed into a large cube of ice u Radiation studied by ANITA detector n Frequency & angular distributions matched theory u Refraction affects angular dist. n Previous expts. with salt and sand targets ANITA Collab., 2007

Ray Tracing in Antarctic Ice n The varying density near the surface causes radio waves to refract n Density profile measured with boreholes. n Slowest transition to pure ice in central Antarctica Depth (m) Density (Mg/m 3 )