Testing models of new physics with UHE air shower observations

Understand

Several air shower observatories have established that the number of muons produced in UHE air showers is significantly larger than that predicted by models.

• We argue that the only solution to this muon deficit, compatible with the observed Xmax distributions, is to reduce the transfer of energy from the hadronic shower into the EM shower, by reducing the production or decay of pi0s.
• We present four different models of new physics, each with a theoretical rationale, which can accomplish this.
• One has a pure proton composition and three have mixed composition.