Measurements in the Forward Phase-Space with the CMS Experiment and their Impact on Physics of Extensive Air Showers

The astrophysical interpretation of ultra-high energy cosmic rays is based on detection of extensive air showers in indirect measurements. Hadronic interaction models that are needed for such analyses require parameters to be adjusted to collider data since soft particle production cannot be calculated from first principles. Within this work, the program CRMC was developed that unifies all air shower hadronic interaction models and supports the output formats used by collider experiments. Almost all LHC experiments have adopted the use these hadronic interaction models thanks to CRMC. The program can even be used in detector simulations to make direct comparison to reconstructed quantities from which the cosmic ray and the particle physics communities benefit immensely. Furthermore, nuclear effects were studied with the CMS experiments at the LHC. The production cross section was derived in recent proton-lead collision data at sqrt(s(NN)) = 5.02 TeV in order to study nuclear effects. The measurement constrains corrections on the cross section calculation known from theory. Diffractive collisions that influence the energy transport in air showers were studied with the CASTOR calorimeter. Only half of the tested models show a good agreement to the data. The highlight of this work is a global likelihood analysis that not only directly connects measurements in the forward phase-space to the physics of air showers but achieves to constrain parameters of hadronic interaction models from astrophysical priors. The analysis method has the potential to revolutionise how model parameters are tuned in the future and it is planned to extend this further.