Unusual Near-horizon Cosmic-ray-like Events Observed by ANITA-IV

Abstract

ANITA's fourth long-duration balloon flight in late 2016 detected 29 cosmic-ray (CR)-like events on a background of $0.37_{-0.17}^{+0.27}$ anthropogenic events. CRs are mainly seen in reflection off the Antarctic ice sheets, creating a characteristic phase-inverted waveform polarity. However, four of the below-horizon CR-like events show anomalous non-inverted polarity, a $p=5.3\times 10^{-4}$ chance if due to background. All anomalous events are from locations near the horizon; ANITA-IV observed no steeply-upcoming anomalous events similar to the two such events seen in prior flights.

6 pages, 4 figures, to appear in Physical Review Letters. Supplemental material (reference 17) available from corresponding author

References in corpus (6)

• The Antarctic Impulsive Transient Antenna Ultra-high Energy Neutrino Detector Design, Performance, and Sensitivity for 2006-2007 Balloon Flight
• Observations of the Askaryan Effect in Ice
• Constraints on the ultra-high energy cosmic neutrino flux from the fourth flight of ANITA
• The Payload for Ultrahigh Energy Observations (PUEO): A White Paper
• First Experimental Characterization of Microwave Emission from Cosmic Ray Air Showers
• Experimental tests of sub-surface reflectors as an explanation for the ANITA anomalous events

Cited by in corpus (17)

• The Payload for Ultrahigh Energy Observations (PUEO): A White Paper
• Tau Neutrinos in the Next Decade: from GeV to EeV
• Probing New Physics at Future Tau Neutrino Telescopes
• Analysis of a Tau Neutrino Origin for the Near-Horizon Air Shower Events Observed by the Fourth Flight of the Antarctic Impulsive Transient Antenna (ANITA)
• The ANITA Anomalous Events and Axion Quark Nuggets
• The POEMMA (Probe of Extreme Multi-Messenger Astrophysics) Observatory
• TAROGE-M: Radio Antenna Array on Antarctic High Mountain for Detecting Near-Horizontal Ultra-High Energy Air Showers
• Gravitational focusing effects on streaming dark matter as a new detection concept
• Experimental tests of sub-surface reflectors as an explanation for the ANITA anomalous events
• Tau depolarization at very high energies for neutrino telescopes
• A search for the anomalous events detected by ANITA using the Pierre Auger Observatory
• Cosmic Rays and the Askaryan Effect Reveal Subsurface Structure and Buried Ice on the Moon
• Characterization of Atmosphere-Skimming Cosmic-Ray Showers in High-Altitude Experiments
• Radio Emission from Atmosphere-Skimming Cosmic Ray Showers in High-Altitude Balloon-Borne Experiments
• POEMMA-Balloon with Radio: A multi-messenger, multi-detector balloon payload
• A possible solution to the mystery of the ANITA anomalous events
• Multi-Modal Clustering Events observed by Horizon-10T and Axion Quark Nuggets