Characteristics of Four Upward-pointing Cosmic-ray-like Events Observed with ANITA

• Main Authors: Gorham, P. W., Nam, J., Romero-Wolf, A., Hoover, S., Allison, P., Banerjee, O., Beatty, J. J., Belov, K., Besson, D. Z., Binns, W. R., Bugaev, V., Cao, P., Chen, C., Chen, P., Clem, J. M., Connolly, A., Dailey, B., Deaconu, C., Cremonesi, L., Dowkonnt, P. F., Duvernois, M. A., Field, R. C., Fox, B. D., Goldstein, D., Gordon, J., Hast, C., Hebert, C. L., Hill, B., Hughes, K., Hupe, R., Israel, M. H., Javaid, A., Kowalski, J., Lam, J., Learned, J. G., Liewer, K. M., Liu, T. C., Link, J. T., Lusczek, E., Matsuno, S., Mercurio, B. C., Miki, C., Miocinovic, P., Mottram, M., Mulrey, K., Naudet, C. J., Ng, J., Nichol, R. J., Palladino, K., Rauch, B. F., Reil, K., Roberts, J., Rosen, M., Rotter, B., Russell, J., Ruckman, L., Saltzberg, D., Seckel, D., Schoorlemmer, H., Stafford, S., Stockham, J., Stockham, M., Strutt, B., Tatem, K., Varner, G. S., Vieregg, A. G., Walz, D., Wissel, S. A., Wu, F.
• Format: Text
• Language: unknown
• Published: arXiv 2016
• Subjects: High Energy Astrophysical Phenomena astro-ph.HE; FOS Physical sciences; Antarctic; The Antarctic; Antarc*
• Online Access: https://dx.doi.org/10.48550/arxiv.1603.05218; https://arxiv.org/abs/1603.05218

We report on four radio-detected cosmic-ray (CR) or CR-like events observed with the Antarctic Impulsive Transient Antenna (ANITA), a NASA-sponsored long-duration balloon payload. Two of the four were previously identified as stratospheric CR air showers during the ANITA-I flight. A third stratospheric CR was detected during the ANITA-II flight. Here we report on characteristics these three unusual CR events, which develop nearly horizontally, 20-30~km above the surface of the Earth. In addition, we report on a fourth steeply upward-pointing ANITA-I CR-like radio event which has characteristics consistent with a primary that emerged from the surface of the ice. This suggests a possible $τ$-lepton decay as the origin of this event, but such an interpretation would require significant suppression of the Standard Model $τ$-neutrino cross section. : 5pp,4 figures, referees' comments addressed, this version accepted to Phys. Rev. Letters. Supplemental PDF material available; see source files