Observation of an Unusual Upward-Going Cosmic-Ray-like Event in the Third Flight of ANITA

• Published in: Physical Review Letters
• Main Authors: Gorham, P. W., Rotter, B., Allison, P., Banerjee, O., Batten, L., Beatty, J. J., Bechtol, K., Belov, K., Besson, D. Z., Binns, W. R., Bugaev, V., Cao, P., Chen, C. C., Chen, C. H., Chen, P., Clem, J. M., Connolly, A., Cremonesi, L., Dailey, B., Deaconu, C., Dowkontt, P. F., Fox, B. D., Gordon, J. W. H., Hast, C., Hill, B., Hughes, K., Huang, J. J., Hupe, R., Israel, M. H., Javaid, A., Lam, J., Liewer, K. M., Lin, S. Y., Liu, T. C., Ludwig, A., Macchiarulo, L., Matsuno, S., Miki, C., Mulrey, K., Nam, J., Naudet, C. J., Nichol, R. J., Novikov, A., Oberla, E., Olmedo, M., Prechelt, R., Prohira, S., Rauch, B. F., Roberts, J. M., Romero-Wolf, A., Russell, J. W., Saltzberg, D., Seckel, D., Schoorlemmer, H., Shiao, J., Stafford, S., Stockham, J., Stockham, M., Strutt, B., Varner, G. S., Vieregg, A. G., Wang, S. H., Wissel, S. A.
• Language: unknown
• Published: 2023
• Subjects: 79 ASTRONOMY AND ASTROPHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Antarctic; The Antarctic; Antarc*
• Online Access: http://www.osti.gov/servlets/purl/1490161; https://www.osti.gov/biblio/1490161; https://doi.org/10.1103/physrevlett.121.161102

We report here on an upward traveling, radio-detected cosmic-ray-like impulsive event with characteristics closely matching an extensive air shower. This event, observed in the third flight of the Antarctic Impulsive Transient Antenna (ANITA), a NASA-sponsored long-duration balloon payload, is consistent with a similar event reported in a previous flight. These events could be produced by the atmospheric decay of an upward-propagating τ lepton produced by a ν τ interaction, although their relatively steep arrival angles create tension with the standard model neutrino cross section. Each of the two events have a posteriori background estimates of ≲ 10 - 2 events. If these are generated by τ -lepton decay, then either the charged-current ν τ cross section is suppressed at EeV energies, or the events arise at moments when the peak flux of a transient neutrino source was much larger than the typical expected cosmogenic background neutrinos.