Thesis defense of Julian Alexander Boelhauve

The impact of precision measurements in high-energy particle physics on astroparticle physics is illuminated in this thesis. Two measurements of light-hadron production performed with the LHCb experiment at CERN are presented. In the first measurement, the differential cross-section of prompt production of long-lived charged particles in proton–proton collisions at a centre-of-mass energy of 13 TeV is determined. The analysis is conducted in intervals of particle kinematics, and the two particle charges are studied separately. In the second measurement, the differential cross-sections of prompt production of charged pions, charged kaons and (anti)protons are analogously determined in two systems: collisions of protons with lead ions at a nucleon–nucleon centre-of-mass energy of 8.16 TeV and proton–proton collisions at 13 TeV. Moreover, hadron-production ratios and nuclear-modification factors are measured. Comparisons with contemporary hadronic-interaction models reveal that none of the models is capable of describing all the observables within the measurement uncertainties. The light-hadron composition measured in proton–proton collisions resembles the decrease in charged-pion production needed in the models to explain the Muon Puzzle in high-energy air showers.