Phased arrays: A strategy to lower the energy threshold for neutrinos

¹ Physics Dept., California Polytechnic State Univ., San Luis Obispo CA, 93407 USA
² Dept. of Physics, Univ. of California Berkeley, Berkeley, CA, 94720 USA
³ Kavli Instit. for Cosmological Physics, Univ. of Chicago, Chicago, Illinois 60637, USA
⁴ Wisconsin IceCube Particle Astrophysics Center, Univ. of Wisconsin-Madison, Madison, WI 53703, USA
⁵ Dept. of Physics and Astronomy, Univ. of California Los Angeles, Los Angeles, CA 90095, USA
⁶ Dept. of Physics and Astronomy, Univ. College London, London, United Kingdom
⁷ Dept. of Physics, Univ. of Chicago, Chicago, IL 60637, USA
⁸ Electrical Engineering Dept., California Polytechnic State Univ., San Luis Obispo, CA 93407, USA
⁹ Dept. of Physics and Astronomy, Univ. of Hawaii, Manoa, HI 96822, USA
¹⁰ Jet Propulsion Laboratory, California Instit. of Technology, Pasadena, CA 91109, USA
¹¹ Dept. of Astronomy and Astrophysics, Univ. of Chicago, Chicago, IL 60637, USA
¹² Department of Physics, Enrico Fermi Institute, Univ. of Chicago, Chicago, Illinois 60637, USA

^* e-mail: swissel@calpoly.edu

Published online: 15 March 2017

Abstract

In-ice radio arrays are optimized for detecting the highest energy, cosmogenic neutrinos expected to be produced though cosmic ray interactions with background photons. However, there are two expected populations of high energy neutrinos: the astrophysical flux observed by IceCube (~1 PeV) and the cosmogenic flux (~ 10¹⁷ eV or 100 PeV). Typical radio arrays employ a noise-riding trigger, which limits their minimum energy threshold based on the background noise temperature of the ice. Phased radio arrays could lower the energy threshold by combining the signals from several channels before triggering, thereby improving the signal-to-noise at the trigger level. Reducing the energy threshold would allow radio experiments to more efficiently overlap with optical Cherenkov neutrino telescopes as well as for more efficient searches for cosmogenic neutrinos. We discuss the proposed technique and prototypical phased arrays deployed in an anechoic chamber and at Greenland’s Summit Station.