Extreme Energy Particle Astrophysics with ANITA-V - Washington University Co-I

This is a Co-I proposal that should be cross-referenced to the University of Hawaii proposal titled “Extreme Energy Particle Astrophysics with ANITA-V”, for which Peter Gorham is the Principal Investigator. ANITA seeks to detect and elucidate the sources of the highest energy particles in the universe via measurements of cosmogenic ultra-high energy neutrinos. Such neutrinos are in many cases predicted to be the only unattenuated astrophysical messengers that arrive at Earth with precise directional information, since neutrinos are neutral particles with very weak interactions with matter in intergalactic space. Neutrinos that ANITA seeks to detect will signal the presence of the most extreme astrophysical accelerators and environments, and complement the information available via electromagnetic messengers from gamma-rays to radio waves. ANITA uses a long-duration balloon payload equipped with 48 dual-polarization horn antennas to detect radio impulses in the frequency range 200-1200 MHz, within which the properties of cold Antarctic ice include extreme radio-transparency and depths of up to 4 km. If a neutrino interacts anywhere within the ice sheet in ANITA's view from stratospheric altitudes, we can detect the emerging radio impulse and determine its direction and other characteristics with high precision. This in turn allows us to select candidate neutrinos from among the thermal and anthropogenic backgrounds with high confidence, and to derive angular information about the arrival direction of such candidates as well. Recently ANITA analysis investigated a new detection channel, which focuses on tau-lepton-generating neutrinos, which lead to a unique experimental signature for which ANITA has potentially very high sensitivity, and a candidate event has been detected in prior data. This new detection channel has added to the variety of methods by which ANITA continues to improve its sensitivity and reach into predicted models for cosmogenic neutrinos, for which ANITA has among the best constraints of any detector to date. ANITA is currently the only active NASA mission with the capability to measure ultra-high energy neutrinos, and ANITA's ultra-high energy neutrino sensitivity while on orbit is unmatched by any other instrument, ground- or space-based. As such it is a direct contributor to our understanding of the origin and evolution of the universe, through astrophysical messengers that provide unique information about the most extreme and energetic objects in the cosmos.