A new trigger for detection of PeV to EeV neutrinos using a phased radio array

The detection of high energy neutrinos (1015 -1020 eV or 1-105 PeV) is an important step toward understanding the most energetic cosmic accelerators, and would enable tests of fundamental physics at energy scales that cannot easily be achieved on Earth. In this energy range, there are two expected populations of neutrinos: the astrophysical flux observed with IceCube at lower energies (- 1 PeV) and the predicted cosmogenic flux at higher energies (- 1018 eV). Radio detector arrays such as RICE, ANITA, ARA, and ARIANNA exploit the Askaryan effect and the radio transparency of glacial ice, which together enable enormous volumes of ice to be monitored with sparse instrumentation. We describe here the design for a phased radio array that would lower the energy threshold of radio techniques to the PeV scale, allowing measurement of the astrophysical flux observed with IceCube over an extended energy range. Meaningful energy overlap with optical Cherenkov experiments could be used for energy calibration. The phased radio array design would also provide efficient coverage of the large effective volume required to discover cosmogenic neutrinos.