Unusual Near-Horizon Cosmic-Ray-like Events Observed by ANITA-IV

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; 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

doi:10.1103/PhysRevLett.126.071103

Unusual Near-Horizon Cosmic-Ray-like Events Observed by ANITA-IV

Phys Rev Lett. 2021 Feb 19;126(7):071103. doi: 10.1103/PhysRevLett.126.071103.

Authors

P W Gorham¹, A Ludwig², C Deaconu², P Cao³, P Allison⁴, O Banerjee⁴, L Batten⁵, D Bhattacharya⁶, J J Beatty⁴, K Belov⁷, W R Binns⁸, V Bugaev⁸, C H Chen⁹, P Chen⁹, Y Chen⁹, J M Clem³, L Cremonesi⁵, B Dailey⁴, P F Dowkontt⁸, B D Fox¹, J W H Gordon⁴, C Hast¹⁰, B Hill¹, S Y Hsu⁹, J J Huang⁹, K Hughes⁴, R Hupe⁴, M H Israel⁸, T C Liu¹¹, L Macchiarulo¹, S Matsuno¹, K McBride⁴, C Miki¹, J Nam⁹, C J Naudet⁷, R J Nichol⁵, A Novikov^{12

13}, E Oberla², M Olmedo¹, R Prechelt¹, B F Rauch⁸, J M Roberts¹, A Romero-Wolf⁷, B Rotter¹, J W Russell¹, D Saltzberg¹⁴, D Seckel³, H Schoorlemmer¹⁵, J Shiao⁹, S Stafford⁴, J Stockham¹², M Stockham¹², B Strutt¹⁴, M S Sutherland², G S Varner¹, A G Vieregg², S H Wang⁹, S A Wissel¹⁶

Affiliations

¹ Department of Physics and Astronomy, University of Hawaii, Manoa, Hawaii 96822, USA.
² Department of Physics, Enrico Fermi Institute, Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637, USA.
³ Department of Physics, University of Delaware, Newark, Delaware 19716, USA.
⁴ Department of Physics, Center for Cosmology and AstroParticle Physics, The Ohio State University, Columbus, Ohio 43210, USA.
⁵ Department of Physics and Astronomy, University College London, WC1E 6BT London, United Kingdom.
⁶ Department of Mathematics, George Washington University, Washington, D.C. 20052, USA.
⁷ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA.
⁸ Department of Physics and McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
⁹ Department of Physics, Graduate Institute of Astrophysics, and Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei 10617, Taiwan.
¹⁰ SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
¹¹ Department of Electrophysics, National Yang-Ming Chiao Tung University, Hsinchu 30010, Taiwan.
¹² Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA.
¹³ National Research Nuclear University, Moscow Engineering Physics Institute, Moscow 115409, Russia.
¹⁴ Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA.
¹⁵ Max-Planck-Institute für Kernphysik, 69029 Heidelberg, Germany.
¹⁶ Department of Physics, Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, Pennsylvania 16801, USA.

PMID: 33666466
DOI: 10.1103/PhysRevLett.126.071103

Abstract

ANITA's fourth long-duration balloon flight in 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 phase-inverted waveform polarity. However, four of the below-horizon CR-like events show anomalous noninverted polarity, a p=5.3×10^{-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.