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arXiv · 2008.05690

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

ANITA Collaboration·P. W. Gorham·A. Ludwig·C. Deaconu·P. Cao·P. Allison·O. Banerjee·L. Batten·D. Bhattacharya·J. J. Beatty·K. Belov·W. R. Binns·V. Bugaev·C. H. Chen·P. Chen·Y. Chen·J. M. Clem·L. Cremonesi·B. Dailey·P. F. Dowkontt·B. D. Fox·J. W. H. Gordon·C. Hast·B. Hill·S. Y. Hsu·J. J. Huang·K. Hughes·R. Hupe·M. H. Israel·T. C. Liu·L. Macchiarulo·S. Matsuno·K. McBride·C. Miki·J. Nam·C. J. Naudet·R. J. Nichol·A. Novikov·E. Oberla·M. Olmedo·R. Prechelt·S. Prohira·B. F. Rauch·J. M. Roberts·A. Romero-Wolf·B. Rotter·J. W. Russell·D. Saltzberg·D. Seckel·H. Schoorlemmer·J. Shiao·S. Stafford·J. Stockham·M. Stockham·B. Strutt·M. S. Sutherland·G. S. Varner·A. G. Vieregg·S. H. Wang·S. A. Wissel
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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.

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ANITA Collaboration, P. W. Gorham, A. Ludwig, C. Deaconu, P. Cao, P. Allison, O. Banerjee, L. Batten, D. Bhattacharya, J. J. Beatty, K. Belov, W. R. Binns, V. Bugaev, C. H. Chen, P. Chen, Y. Chen, J. M. Clem, L. Cremonesi, B. Dailey, P. F. Dowkontt, B. D. Fox, J. W. H. Gordon, C. Hast, B. Hill, S. Y. Hsu, J. J. Huang, K. Hughes, R. Hupe, M. H. Israel, T. C. Liu, L. Macchiarulo, S. Matsuno, K. McBride, C. Miki, J. Nam, C. J. Naudet, R. J. Nichol, A. Novikov, E. Oberla, M. Olmedo, R. Prechelt, S. Prohira, B. F. Rauch, J. M. Roberts, A. Romero-Wolf, B. Rotter, J. W. Russell, D. Saltzberg, D. Seckel, H. Schoorlemmer, J. Shiao, S. Stafford, J. Stockham, M. Stockham, B. Strutt, M. S. Sutherland, G. S. Varner, A. G. Vieregg, S. H. Wang, S. A. Wissel. 2020-08-13. Unusual Near-horizon Cosmic-ray-like Events Observed by ANITA-IV. https://doi.org/10.1103/physrevlett.126.071103

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