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 $0.37^{+0.27}_{-0.17}$ 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.
- Publication:
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arXiv e-prints
- Pub Date:
- August 2020
- DOI:
- 10.48550/arXiv.2008.05690
- arXiv:
- arXiv:2008.05690
- Bibcode:
- 2020arXiv200805690A
- Keywords:
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- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 6 pages, 4 figures, to appear in Physical Review Letters. Supplemental material (reference 17) available from corresponding author