Constraints on the ultra-high energy cosmic neutrino flux from the fourth flight of ANITA

Understand

The ANtarctic Impulsive Transient Antenna (ANITA) NASA long-duration balloon payload completed its fourth flight in December 2016, after 28 days of flight time.

• ANITA is sensitive to impulsive broadband radio emission from interactions of ultra-high-energy neutrinos in polar ice (Askaryan emission).
• We present the results of two separate blind analyses searching for signals from Askaryan emission in the data from the fourth flight of ANITA.
• The more sensitive analysis, with a better expected limit, has a background estimate of $0.64^{+0.69}_{-0.45}$ and an analysis efficiency of $82\pm2\%$.