Characteristics of Four Upward-pointing Cosmic-ray-like Events Observed   with ANITA
  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 $\tau$-lepton decay as the origin of this event, but such an interpretation would require significant suppression of the Standard Model ${\tau}$-neutrino cross section. 
P.W.Gorham, J.Nam, A.Romero-Wolf, S.Hoover, P.Allison, O.Banerjee,   J.J.Beatty, K.Belov, D.Z.Besson, W.R.Binns, V.Bugaev, P...
astro-ph.HE