Analyzing Cosmic Ray Data Collected with the Belle II Detector

This thesis studies cosmic ray muons recorded with the Belle II detector. The goal is to measure the angular flux distribution of these muons. Special attention is given to the challenges that arise because the detector was designed for collisions at the SuperKEKB accelerator and not for particles entering from above. Cosmic ray events are selected and corrected using Monte Carlo simulations. Detector effects, reconstruction inefficiencies, and trigger responses are taken into account using a response matrix. The measured angular distribution is found to follow the expected cos^2(α) behavior. The results show that the Belle II detector can be used to study cosmic ray muons and provide a basis for future improvements and extended measurements.