Air showers observed with E>1020 eV pose a problem since protons at such energies cannot survive a long journey through the 2.7 K microwave background. It is suggested that they are initiated instead by neutrinos which become strongly interacting through exchanges of gauge bosons associated with generation-changing neutral currents, a suggestion which is supported by calculations in a dualized standard model recently proposed. In turn, the suggestion bounds the mass of the gauge bosons and gives estimates for the branching ratios of FCNC s, c, b, and t meson decays which are accessible to experiments now being planned.
@article{arxiv.hep-ph/9705463,
title = {Possible Explanation for $E > 10^{20}$ eV Air Showers with Flavour-Changing Neutral Currents},
author = {J. Bordes and H. M. Chan and J. Faridani and J. Pfaudler and S. T. Tsou},
journal= {arXiv preprint arXiv:hep-ph/9705463},
year = {2007}
}