Study of the Hoyle State in 12C using the Lund-York-Cologne-Calorimeter (LYCCA) array

This thesis presents an analysis of the particle-decay behavior of excited 12C states using the LYCCA detector setup. The setup was upgraded to 24 mounted DSSSDs and 18 AIDA FEE data acquisition modules, allowing for the detection of over 3×10^10 scattered ions across two experiments performed in December 2019 and January 2020. Among these, more than 6 × 10^6 particle-decay events, consisting of 4 alpha particles each, of the Hoyle state decay were identified and analyzed, representing the largest dataset for Hoyle state decay studies to date. The thesis details a series of methodological improvements, including the development of a new event-analysis pipeline, time-walk correction, and refined analysis logic, which collectively improved the precision and efficiency of data processing. Additionally, new gate conditions and detector position offset corrections were implemented to enhance data selection and spatial resolution. The calibration and analysis tools developed during this work also contributed to reducing the time required from data acquisition to center-of mass frame analysis of the detected particles. These developments have improved the capabilities of the LYCCA setup, providing a solid foundation for future studies of excited nuclear states and their decay pathways. While the energy resolution in the center-of-mass frame of the particle decay of the excited Carbon nuclei did not allow for establishing a new upper limit, the measured branching ratios are consistent with previous studies, providing additional data points for investigating the structure of higher-lying states in 12C. Additionally, ongoing improvements in the data analysis pipeline have shown promising results for future studies, even on the current dataset.