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...se Emission in Air Showers… 103 coherent up to about 10 MHz whereas in dense materials, the shower has dimensions on the order of a meter, and is coherent up to about 10 GHz (however, materials such as ice are only radio-transparent up to about 1 GHz). [7] Cherenkov radiation, the dominant source of radio emission in dense materials for ultra-high energy particles, develops here as a result of a ~20% excess of charge from positron annihilation and Compton scattering of shower electrons. The process is facilitated by the density of the material, and is far stronger than any such effect in air. [8] This effect also dominates other emissions such as optical Cherenkov radiation or fluorescence for energies above about 1016 eV, making it well suited to the observation of UHE cosmic rays. [9] This is because the energy of visible Cherenkov radiation EC is proportional to the energy of the primary particle EP, but that EC is proportional to EP 2 for radio Cherenkov radiation. If the primary particle (in this case, a neutrino) has high enough energy, radio Cherenkov dominates the emission. [8] Despite the fact that Askaryan predicted this effect in the early 1960’s, experimental evidence was ...

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...ements performed at SLAC using silica sand in 2000 [2] and again in using salt in 2002. [11] Once the so-called Askaryan effect was confirmed, experiments searching for ultra-high energy neutrinos via radio emission in dense materials began to develop. The first such experiment was the Goldstone Lunar Ultra-high energy neutrino Experiment (GLUE) in 1999. [12] Radio Ice Cherenkov Experiment (RICE) is currently under operation [10]; ANtarctic Impulsive Transient Antenna (ANITA) successfully launched a prototype ANITA-LITE in 2003 and is set to fly a full-scale version of the experiment in 2006. [16] Finally, Salt dome Shower Array (SalSA) is currently under development. [11] 2. The Physics of Radio Emission in Air Showers Before the 1960s, most experiments detected cosmic rays via scintillators and photomultiplier tubes in optical frequencies. After Galbraith and Jelley discovered extensive air showers (EAS) were accompanied by Cherenkov radiation in the 1950s, Jelley questioned if the radiation extended to radio frequencies, and thus whether or not current optical detectors could be supplemented with radio detectors. Kahn and Lerche, 102 E.R. Lusczek and later Colgate, showed that coher...

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... uses radio Cherenkov emission in Antarctic ice to detect ultra-high energy neutrinos with an effective volume of 106 km3. ANITA-LITE, a prototype of ANITA, was launched on December 17, 2003 and flew for 18 days, piggybacked on the TIGER balloon payload. [16] The flight successfully showed that Antarctica is a suitably RFquiet environment for neutrino detection, and provided a test of detector design. Figure 1 shows ANITA-LITE’s constraints on neutrino fluxes as related to the neutrino flux from the Z-burst model, which, when taken with GLUE [12] and FORTE [13] results, rules it out entirely. [17] The full-scale version of ANITA will be the first neutrino experiment with enough sensitivity to effectively probe GZK neutrinos, also shown in figure 1. Its first flight is scheduled for December 2006. [16] Figure 1. Neutrino fluxes constrained by AMANDA, RICE, GLUE, FORTE, and ANITALITE, plus predicted GZK fluxes and projected ANITA results. Courtesy of the ANITA collaboration. [17] 104 E.R. Lusczek Salt dome Shower Array (SalSA) is a proposed experiment that will look for UHE neutrinos in salt domes. Saltzberg et al.’s accelerator tests performed in June of 2002 successfully confirmed seve...