ANtarctic Impulsive Transient Antenna (ANITA) is a NASA long duration balloon mission that tests the fundamental nature of high energy physics and astrophysics through ultra-high energy neutrino astrophysics. Neutrinos and gravitational waves are the only direct astrophysical messengers that reach earth unattenuated through space at all energies. ANITA probes both the nature of the sources of these extreme particles, and the fundamental interactions of high energy physics at extreme scales.
The ANITA instrument aims to detect ultra-high energy neutrinos through two independent channels. The first is via the Askaryan effect – coherent radio emission that is produced by the cascade of particles created in a high-energy particle interaction in a dielectric material. The second is via radio emission from upward-going showers of particles in the atmosphere, induced by a tau neutrino interactions in the Earth and the subsequent decay of the daughter tau lepton.
ANITA is unique in that it monitors an extremely large instantaneous volume of ice and atmosphere, which is a requirement for searching for these extremely energetic neutrinos. From 40 km above the surface, ANITA monitors a large volume of ice in Antarctica looking for fast neutrino-induced Askaryan signals, and a large volume of atmosphere looking for neutrino-induced air showers. ANITA has flown four times, and has produced world-leading constraints on the ultra-high energy neutrino flux in the 10^19.5 – 10^20 eV range.
A next-generation balloon-borne payload, PUEO, has been proposed, which will significantly improve on the sensitivity of ANITA, with more antenna collecting area and improved trigger technology that can more efficiently distinguish neutrino-like signals from background.
Abigail Vieregg
Senior Member