Cosmic Ray Spectrum “Knee”: A Herald of New Physics?

We argue that the knee in the cosmic ray spectrum at energies E > ∼ 10 15.5 eV is due to “new physics”, namely to a channel in the high energy ( > ∼ TeV in the CM) proton interactions hitherto unaccounted for in estimating the energies of the air shower cosmic rays. The new interaction transfers part of the primary particle’s energy to modes which do not trigger the experimental arragement (neutrinos, lightest supersymmetric particle, gravitons ) thus underestimating its true energy. We show that this underestimate leads naturally to the observed break (the “knee”) in the inferred cosmic ray spectrum. The suggestion we advance fits nicely to current theoretical extensions of the Standard Model (supersymmetry, technicolor, low scale gravity) where new physics at the TeV scale manifests with the distinct signature of missing energy. We present a simple model where the new physics proceeds via gluon fusion and assuming a single power law for the galactic (E < ∼ 10 18.5 eV) cosmic ray spectrum, we produce a good fit to the data in the 10 − 1018.5 eV range. Our proposal should be testable in laboratory experiments (LHC) in the near future and, should it be proven correct, it would signal besides the presence of new physics in high energy interactions, a drastically different interpretation of the sources and acceleration of cosmic rays.