In the case of the upward-pointing cosmic rays, Fox and his colleagues argue that they are consistent with some of the predicted characteristics of the “stau,” the supersymmetric partner of the tau, which cannot be explained using the Standard Model of physics. The supersymmetric models predict that as a stau passes through Earth from space, it decays into a tau lepton and an as yet undetected lowest-mass supersymmetric particle before emerging on the other side of Earth—where the tau lepton could be registered by instruments like ANITA.

To arrive at this conclusion, Fox and his colleagues first demonstrated that the events observed by ANITA are not interpretable within the Standard Model. In the first place, the trajectories of the particles are “highly improbable” under the Standard Model. As Fox and his colleagues argue, to produce these trajectories using the Standard Model would require neutrino fluxes, or the number of neutrinos hitting a certain area in a certain amount of time, “well in excess” of those that have been cataloged by various cosmic ray observatories. Furthermore, they argued that the steepness of the angles of the cosmic rays are also highly improbable within the Standard Model.