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The Pierre Auger Collaboration has reported an excess in the number of muonsof a few tens of percent over expectations computed using extrapolation ofhadronic interaction models tuned to accommodate LHC data. Very recently, weproposed an explanation for the muon excess assuming the formation of adeconfined quark matter (fireball) state in central collisions ofultrarelativistic cosmic rays with air nuclei. At the first stage of itsevolution the fireball contains gluons as well as $u$ and $d$ quarks. The veryhigh baryochemical potential inhibits gluons from fragmenting into $u \bar u$and $d \bar d$, and so they fragment predominantly into $s \bar s$ pairs. Inthe hadronization which follows this leads to the strong suppression of pionsand hence photons, but allows heavy hadrons to be emitted carrying awaystrangeness. In this manner, the extreme imbalance of hadron to photon contentprovides a way to enhance the muon content of the air shower. In thiscommunication we study theoretical systematics from hadronic interaction modelsused to describe the cascades of secondary particles produced in the fireballexplosion. We study the predictions of one of the leading LHC-tuned modelsQGSJET II-04 considered in the Auger analysis.

Probing QCD approach to thermal equilibrium with ultrahigh energy cosmic rays