Hadron Production in 120 GeV/$c$ Proton-Carbon Interactions

This thesis presents multiplicity measurements of $\pi^\pm$, $p/\bar{p}$, and $K^\pm$ in 120 GeV/$c$ proton-carbon interactions. The measurements were made using data collected at the NA61/SHINE experiment in 2016 and 2017. The experimental data sets were recorded using two complementary detector configurations, with increased phase space coverage in 2017 due to the addition of new subdetectors. This thesis details the design, construction, and performance of these detectors. Comparisons of the measured hadron multiplicities show significant discrepancies with popular Monte Carlo models, indicating the need for improvement in hadron production modeling. These multiplicity measurements can be used by Monte Carlo modeling groups to improve the models, and will also help current and future long-baseline neutrino oscillation experiments estimate neutrino beam fluxes with higher accuracy.