The Antarctic Impulsive Transient Antenna, or ANITA, has detected two unusual signals.
ANITA floats on a helium balloon 37000 meters high for a month at a time. It searches for the signals of high-energy particles from space, including lightweight, ghostly particles called neutrinos. Those neutrinos can interact within Antarctica’s ice, producing radio waves that are picked up by ANITA’s antennas.
It appears to be from extremely energetic neutrinos shooting skyward from within the Earth. But high-energy neutrinos can’t pass through as much material as lower-energy neutrinos can. So although high-energy neutrinos can skim the edges of the planet, they won’t survive a pass straight through.
Either new high-energy neutrinos have been detected that are less likely to react to the Earth’s matter or there was some kind of error in the analysis.
The ANITA collaboration have reported observation of two anomalous events that appear to be εcr≈0.6 EeV cosmic ray showers emerging from the Earth with exit angles of 27∘ and 35∘, respectively. While EeV-scale upgoing showers have been anticipated as a result of astrophysical tau neutrinos converting to tau leptons during Earth passage, the observed exit angles are much steeper than expected in Standard Model (SM) scenarios. Indeed, under conservative extrapolations of the SM interactions, there is no particle that can propagate through the Earth with probability p>10−6 at these energies and exit angles. We explore here whether “beyond the Standard Model” (BSM) particles are required to explain the ANITA events, if correctly interpreted, and conclude that they are. Seeking confirmation or refutation of the physical phenomenon of sub-EeV Earth-emergent cosmic rays in data from other facilities, we find support for the reality of the ANITA events, and three candidate analog events, among the Extremely High Energy Northern Track neutrinos of the IceCube Neutrino Observatory. Properties of the implied BSM particle are anticipated, at least in part, by those predicted for the “stau” slepton (τ̃ R) in some supersymmetric models of the fundamental interactions, wherein the stau manifests as the next-to-lowest mass supersymmetric partner particle.